rel-38
217 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Hou Tao
|
667ea9b6cf |
bpf: Cancel the running bpf_timer through kworker for PREEMPT_RT
BugLink: https://bugs.launchpad.net/bugs/2111953
[ Upstream commit 58f038e6d209d2dd862fcf5de55407855856794d ]
During the update procedure, when overwrite element in a pre-allocated
htab, the freeing of old_element is protected by the bucket lock. The
reason why the bucket lock is necessary is that the old_element has
already been stashed in htab->extra_elems after alloc_htab_elem()
returns. If freeing the old_element after the bucket lock is unlocked,
the stashed element may be reused by concurrent update procedure and the
freeing of old_element will run concurrently with the reuse of the
old_element. However, the invocation of check_and_free_fields() may
acquire a spin-lock which violates the lockdep rule because its caller
has already held a raw-spin-lock (bucket lock). The following warning
will be reported when such race happens:
BUG: scheduling while atomic: test_progs/676/0x00000003
3 locks held by test_progs/676:
#0: ffffffff864b0240 (rcu_read_lock_trace){....}-{0:0}, at: bpf_prog_test_run_syscall+0x2c0/0x830
#1: ffff88810e961188 (&htab->lockdep_key){....}-{2:2}, at: htab_map_update_elem+0x306/0x1500
#2: ffff8881f4eac1b8 (&base->softirq_expiry_lock){....}-{2:2}, at: hrtimer_cancel_wait_running+0xe9/0x1b0
Modules linked in: bpf_testmod(O)
Preemption disabled at:
[<ffffffff817837a3>] htab_map_update_elem+0x293/0x1500
CPU: 0 UID: 0 PID: 676 Comm: test_progs Tainted: G ... 6.12.0+ #11
Tainted: [W]=WARN, [O]=OOT_MODULE
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)...
Call Trace:
<TASK>
dump_stack_lvl+0x57/0x70
dump_stack+0x10/0x20
__schedule_bug+0x120/0x170
__schedule+0x300c/0x4800
schedule_rtlock+0x37/0x60
rtlock_slowlock_locked+0x6d9/0x54c0
rt_spin_lock+0x168/0x230
hrtimer_cancel_wait_running+0xe9/0x1b0
hrtimer_cancel+0x24/0x30
bpf_timer_delete_work+0x1d/0x40
bpf_timer_cancel_and_free+0x5e/0x80
bpf_obj_free_fields+0x262/0x4a0
check_and_free_fields+0x1d0/0x280
htab_map_update_elem+0x7fc/0x1500
bpf_prog_9f90bc20768e0cb9_overwrite_cb+0x3f/0x43
bpf_prog_ea601c4649694dbd_overwrite_timer+0x5d/0x7e
bpf_prog_test_run_syscall+0x322/0x830
__sys_bpf+0x135d/0x3ca0
__x64_sys_bpf+0x75/0xb0
x64_sys_call+0x1b5/0xa10
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
...
</TASK>
It seems feasible to break the reuse and refill of per-cpu extra_elems
into two independent parts: reuse the per-cpu extra_elems with bucket
lock being held and refill the old_element as per-cpu extra_elems after
the bucket lock is unlocked. However, it will make the concurrent
overwrite procedures on the same CPU return unexpected -E2BIG error when
the map is full.
Therefore, the patch fixes the lock problem by breaking the cancelling
of bpf_timer into two steps for PREEMPT_RT:
1) use hrtimer_try_to_cancel() and check its return value
2) if the timer is running, use hrtimer_cancel() through a kworker to
cancel it again
Considering that the current implementation of hrtimer_cancel() will try
to acquire a being held softirq_expiry_lock when the current timer is
running, these steps above are reasonable. However, it also has
downside. When the timer is running, the cancelling of the timer is
delayed when releasing the last map uref. The delay is also fixable
(e.g., break the cancelling of bpf timer into two parts: one part in
locked scope, another one in unlocked scope), it can be revised later if
necessary.
It is a bit hard to decide the right fix tag. One reason is that the
problem depends on PREEMPT_RT which is enabled in v6.12. Considering the
softirq_expiry_lock lock exists since v5.4 and bpf_timer is introduced
in v5.15, the bpf_timer commit is used in the fixes tag and an extra
depends-on tag is added to state the dependency on PREEMPT_RT.
Fixes:
|
||
 Daniel Borkmann
|
6b4c6acf77 |
bpf: Add MEM_WRITE attribute
BugLink: https://bugs.launchpad.net/bugs/2097575 [ Upstream commit 6fad274f06f038c29660aa53fbad14241c9fd976 ] Add a MEM_WRITE attribute for BPF helper functions which can be used in bpf_func_proto to annotate an argument type in order to let the verifier know that the helper writes into the memory passed as an argument. In the past MEM_UNINIT has been (ab)used for this function, but the latter merely tells the verifier that the passed memory can be uninitialized. There have been bugs with overloading the latter but aside from that there are also cases where the passed memory is read + written which currently cannot be expressed, see also 4b3786a6c539 ("bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error"). Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20241021152809.33343-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov <ast@kernel.org> Stable-dep-of: 8ea607330a39 ("bpf: Fix overloading of MEM_UNINIT's meaning") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com> Signed-off-by: Stefan Bader <stefan.bader@canonical.com> |
||
|
Daniel Borkmann
|
637deaf56f |
bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error
BugLink: https://bugs.launchpad.net/bugs/2089340 [ Upstream commit 4b3786a6c5397dc220b1483d8e2f4867743e966f ] For all non-tracing helpers which formerly had ARG_PTR_TO_{LONG,INT} as input arguments, zero the value for the case of an error as otherwise it could leak memory. For tracing, it is not needed given CAP_PERFMON can already read all kernel memory anyway hence bpf_get_func_arg() and bpf_get_func_ret() is skipped in here. Also, the MTU helpers mtu_len pointer value is being written but also read. Technically, the MEM_UNINIT should not be there in order to always force init. Removing MEM_UNINIT needs more verifier rework though: MEM_UNINIT right now implies two things actually: i) write into memory, ii) memory does not have to be initialized. If we lift MEM_UNINIT, it then becomes: i) read into memory, ii) memory must be initialized. This means that for bpf_*_check_mtu() we're readding the issue we're trying to fix, that is, it would then be able to write back into things like .rodata BPF maps. Follow-up work will rework the MEM_UNINIT semantics such that the intent can be better expressed. For now just clear the *mtu_len on error path which can be lifted later again. Fixes: |
||
|
Daniel Borkmann
|
f48688033c |
bpf: Fix helper writes to read-only maps
BugLink: https://bugs.launchpad.net/bugs/2089340
[ Upstream commit 32556ce93bc45c730829083cb60f95a2728ea48b ]
Lonial found an issue that despite user- and BPF-side frozen BPF map
(like in case of .rodata), it was still possible to write into it from
a BPF program side through specific helpers having ARG_PTR_TO_{LONG,INT}
as arguments.
In check_func_arg() when the argument is as mentioned, the meta->raw_mode
is never set. Later, check_helper_mem_access(), under the case of
PTR_TO_MAP_VALUE as register base type, it assumes BPF_READ for the
subsequent call to check_map_access_type() and given the BPF map is
read-only it succeeds.
The helpers really need to be annotated as ARG_PTR_TO_{LONG,INT} | MEM_UNINIT
when results are written into them as opposed to read out of them. The
latter indicates that it's okay to pass a pointer to uninitialized memory
as the memory is written to anyway.
However, ARG_PTR_TO_{LONG,INT} is a special case of ARG_PTR_TO_FIXED_SIZE_MEM
just with additional alignment requirement. So it is better to just get
rid of the ARG_PTR_TO_{LONG,INT} special cases altogether and reuse the
fixed size memory types. For this, add MEM_ALIGNED to additionally ensure
alignment given these helpers write directly into the args via *<ptr> = val.
The .arg*_size has been initialized reflecting the actual sizeof(*<ptr>).
MEM_ALIGNED can only be used in combination with MEM_FIXED_SIZE annotated
argument types, since in !MEM_FIXED_SIZE cases the verifier does not know
the buffer size a priori and therefore cannot blindly write *<ptr> = val.
Fixes:
|
||
|
Daniel Borkmann
|
4822ba084f |
bpf: Fix bpf_strtol and bpf_strtoul helpers for 32bit
BugLink: https://bugs.launchpad.net/bugs/2089340
[ Upstream commit cfe69c50b05510b24e26ccb427c7cc70beafd6c1 ]
The bpf_strtol() and bpf_strtoul() helpers are currently broken on 32bit:
The argument type ARG_PTR_TO_LONG is BPF-side "long", not kernel-side "long"
and therefore always considered fixed 64bit no matter if 64 or 32bit underlying
architecture.
This contract breaks in case of the two mentioned helpers since their BPF_CALL
definition for the helpers was added with {unsigned,}long *res. Meaning, the
transition from BPF-side "long" (BPF program) to kernel-side "long" (BPF helper)
breaks here.
Both helpers call __bpf_strtoll() with "long long" correctly, but later assigning
the result into 32-bit "*(long *)" on 32bit architectures. From a BPF program
point of view, this means upper bits will be seen as uninitialised.
Therefore, fix both BPF_CALL signatures to {s,u}64 types to fix this situation.
Now, changing also uapi/bpf.h helper documentation which generates bpf_helper_defs.h
for BPF programs is tricky: Changing signatures there to __{s,u}64 would trigger
compiler warnings (incompatible pointer types passing 'long *' to parameter of type
'__s64 *' (aka 'long long *')) for existing BPF programs.
Leaving the signatures as-is would be fine as from BPF program point of view it is
still BPF-side "long" and thus equivalent to __{s,u}64 on 64 or 32bit underlying
architectures.
Note that bpf_strtol() and bpf_strtoul() are the only helpers with this issue.
Fixes:
|
||
 Kumar Kartikeya Dwivedi
|
bdbaaa2750 |
bpf: Defer work in bpf_timer_cancel_and_free
BugLink: https://bugs.launchpad.net/bugs/2078289
[ Upstream commit a6fcd19d7eac1335eb76bc16b6a66b7f574d1d69 ]
Currently, the same case as previous patch (two timer callbacks trying
to cancel each other) can be invoked through bpf_map_update_elem as
well, or more precisely, freeing map elements containing timers. Since
this relies on hrtimer_cancel as well, it is prone to the same deadlock
situation as the previous patch.
It would be sufficient to use hrtimer_try_to_cancel to fix this problem,
as the timer cannot be enqueued after async_cancel_and_free. Once
async_cancel_and_free has been done, the timer must be reinitialized
before it can be armed again. The callback running in parallel trying to
arm the timer will fail, and freeing bpf_hrtimer without waiting is
sufficient (given kfree_rcu), and bpf_timer_cb will return
HRTIMER_NORESTART, preventing the timer from being rearmed again.
However, there exists a UAF scenario where the callback arms the timer
before entering this function, such that if cancellation fails (due to
timer callback invoking this routine, or the target timer callback
running concurrently). In such a case, if the timer expiration is
significantly far in the future, the RCU grace period expiration
happening before it will free the bpf_hrtimer state and along with it
the struct hrtimer, that is enqueued.
Hence, it is clear cancellation needs to occur after
async_cancel_and_free, and yet it cannot be done inline due to deadlock
issues. We thus modify bpf_timer_cancel_and_free to defer work to the
global workqueue, adding a work_struct alongside rcu_head (both used at
_different_ points of time, so can share space).
Update existing code comments to reflect the new state of affairs.
Fixes:
|
||
|
Kumar Kartikeya Dwivedi
|
1e80b985ac |
bpf: Fail bpf_timer_cancel when callback is being cancelled
BugLink: https://bugs.launchpad.net/bugs/2078289
[ Upstream commit d4523831f07a267a943f0dde844bf8ead7495f13 ]
Given a schedule:
timer1 cb timer2 cb
bpf_timer_cancel(timer2); bpf_timer_cancel(timer1);
Both bpf_timer_cancel calls would wait for the other callback to finish
executing, introducing a lockup.
Add an atomic_t count named 'cancelling' in bpf_hrtimer. This keeps
track of all in-flight cancellation requests for a given BPF timer.
Whenever cancelling a BPF timer, we must check if we have outstanding
cancellation requests, and if so, we must fail the operation with an
error (-EDEADLK) since cancellation is synchronous and waits for the
callback to finish executing. This implies that we can enter a deadlock
situation involving two or more timer callbacks executing in parallel
and attempting to cancel one another.
Note that we avoid incrementing the cancelling counter for the target
timer (the one being cancelled) if bpf_timer_cancel is not invoked from
a callback, to avoid spurious errors. The whole point of detecting
cur->cancelling and returning -EDEADLK is to not enter a busy wait loop
(which may or may not lead to a lockup). This does not apply in case the
caller is in a non-callback context, the other side can continue to
cancel as it sees fit without running into errors.
Background on prior attempts:
Earlier versions of this patch used a bool 'cancelling' bit and used the
following pattern under timer->lock to publish cancellation status.
lock(t->lock);
t->cancelling = true;
mb();
if (cur->cancelling)
return -EDEADLK;
unlock(t->lock);
hrtimer_cancel(t->timer);
t->cancelling = false;
The store outside the critical section could overwrite a parallel
requests t->cancelling assignment to true, to ensure the parallely
executing callback observes its cancellation status.
It would be necessary to clear this cancelling bit once hrtimer_cancel
is done, but lack of serialization introduced races. Another option was
explored where bpf_timer_start would clear the bit when (re)starting the
timer under timer->lock. This would ensure serialized access to the
cancelling bit, but may allow it to be cleared before in-flight
hrtimer_cancel has finished executing, such that lockups can occur
again.
Thus, we choose an atomic counter to keep track of all outstanding
cancellation requests and use it to prevent lockups in case callbacks
attempt to cancel each other while executing in parallel.
Reported-by: Dohyun Kim <dohyunkim@google.com>
Reported-by: Neel Natu <neelnatu@google.com>
Fixes:
|
||
 Benjamin Tissoires
|
0e628569a3 |
bpf: replace bpf_timer_init with a generic helper
BugLink: https://bugs.launchpad.net/bugs/2078289 [ Upstream commit 56b4a177ae6322173360a93ea828ad18570a5a14 ] No code change except for the new flags argument being stored in the local data struct. Signed-off-by: Benjamin Tissoires <bentiss@kernel.org> Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-2-6c986a5a741f@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> Stable-dep-of: d4523831f07a ("bpf: Fail bpf_timer_cancel when callback is being cancelled") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Portia Stephens <portia.stephens@canonical.com> Signed-off-by: Stefan Bader <stefan.bader@canonical.com> |
||
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Benjamin Tissoires
|
3a49d56e38 |
bpf: make timer data struct more generic
BugLink: https://bugs.launchpad.net/bugs/2078289 [ Upstream commit be2749beff62e0d63cf97fe63cabc79a68443139 ] To be able to add workqueues and reuse most of the timer code, we need to make bpf_hrtimer more generic. There is no code change except that the new struct gets a new u64 flags attribute. We are still below 2 cache lines, so this shouldn't impact the current running codes. The ordering is also changed. Everything related to async callback is now on top of bpf_hrtimer. Signed-off-by: Benjamin Tissoires <bentiss@kernel.org> Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-1-6c986a5a741f@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> Stable-dep-of: d4523831f07a ("bpf: Fail bpf_timer_cancel when callback is being cancelled") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Portia Stephens <portia.stephens@canonical.com> Signed-off-by: Stefan Bader <stefan.bader@canonical.com> |
||
 Yonghong Song
|
7b035f3b81 |
bpf: Mark bpf_spin_{lock,unlock}() helpers with notrace correctly
BugLink: https://bugs.launchpad.net/bugs/2060097
[ Upstream commit 178c54666f9c4d2f49f2ea661d0c11b52f0ed190 ]
Currently tracing is supposed not to allow for bpf_spin_{lock,unlock}()
helper calls. This is to prevent deadlock for the following cases:
- there is a prog (prog-A) calling bpf_spin_{lock,unlock}().
- there is a tracing program (prog-B), e.g., fentry, attached
to bpf_spin_lock() and/or bpf_spin_unlock().
- prog-B calls bpf_spin_{lock,unlock}().
For such a case, when prog-A calls bpf_spin_{lock,unlock}(),
a deadlock will happen.
The related source codes are below in kernel/bpf/helpers.c:
notrace BPF_CALL_1(bpf_spin_lock, struct bpf_spin_lock *, lock)
notrace BPF_CALL_1(bpf_spin_unlock, struct bpf_spin_lock *, lock)
notrace is supposed to prevent fentry prog from attaching to
bpf_spin_{lock,unlock}().
But actually this is not the case and fentry prog can successfully
attached to bpf_spin_lock(). Siddharth Chintamaneni reported
the issue in [1]. The following is the macro definition for
above BPF_CALL_1:
#define BPF_CALL_x(x, name, ...) \
static __always_inline \
u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
typedef u64 (*btf_##name)(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)); \
u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)) \
{ \
return ((btf_##name)____##name)(__BPF_MAP(x,__BPF_CAST,__BPF_N,__VA_ARGS__));\
} \
static __always_inline \
u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__))
#define BPF_CALL_1(name, ...) BPF_CALL_x(1, name, __VA_ARGS__)
The notrace attribute is actually applied to the static always_inline function
____bpf_spin_{lock,unlock}(). The actual callback function
bpf_spin_{lock,unlock}() is not marked with notrace, hence
allowing fentry prog to attach to two helpers, and this
may cause the above mentioned deadlock. Siddharth Chintamaneni
actually has a reproducer in [2].
To fix the issue, a new macro NOTRACE_BPF_CALL_1 is introduced which
will add notrace attribute to the original function instead of
the hidden always_inline function and this fixed the problem.
[1] https://lore.kernel.org/bpf/CAE5sdEigPnoGrzN8WU7Tx-h-iFuMZgW06qp0KHWtpvoXxf1OAQ@mail.gmail.com/
[2] https://lore.kernel.org/bpf/CAE5sdEg6yUc_Jz50AnUXEEUh6O73yQ1Z6NV2srJnef0ZrQkZew@mail.gmail.com/
Fixes:
|
||
 Martin KaFai Lau
|
0281b919e1 |
bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel
The following race is possible between bpf_timer_cancel_and_free
and bpf_timer_cancel. It will lead a UAF on the timer->timer.
bpf_timer_cancel();
spin_lock();
t = timer->time;
spin_unlock();
bpf_timer_cancel_and_free();
spin_lock();
t = timer->timer;
timer->timer = NULL;
spin_unlock();
hrtimer_cancel(&t->timer);
kfree(t);
/* UAF on t */
hrtimer_cancel(&t->timer);
In bpf_timer_cancel_and_free, this patch frees the timer->timer
after a rcu grace period. This requires a rcu_head addition
to the "struct bpf_hrtimer". Another kfree(t) happens in bpf_timer_init,
this does not need a kfree_rcu because it is still under the
spin_lock and timer->timer has not been visible by others yet.
In bpf_timer_cancel, rcu_read_lock() is added because this helper
can be used in a non rcu critical section context (e.g. from
a sleepable bpf prog). Other timer->timer usages in helpers.c
have been audited, bpf_timer_cancel() is the only place where
timer->timer is used outside of the spin_lock.
Another solution considered is to mark a t->flag in bpf_timer_cancel
and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free,
it busy waits for the flag to be cleared before kfree(t). This patch
goes with a straight forward solution and frees timer->timer after
a rcu grace period.
Fixes:
|
||
 Andrii Nakryiko
|
d17aff807f |
Revert BPF token-related functionality
This patch includes the following revert (one conflicting BPF FS patch and three token patch sets, represented by merge commits): - revert |
||
 Alexei Starovoitov
|
852486b35f |
x86/cfi,bpf: Fix bpf_exception_cb() signature
As per the earlier patches, BPF sub-programs have bpf_callback_t signature and CFI expects callers to have matching signature. This is violated by bpf_prog_aux::bpf_exception_cb(). [peterz: Changelog] Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/CAADnVQ+Z7UcXXBBhMubhcMM=R-dExk-uHtfOLtoLxQ1XxEpqEA@mail.gmail.com Link: https://lore.kernel.org/r/20231215092707.910319166@infradead.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
 Peter Zijlstra
|
e4c0033989 |
bpf: Fix dtor CFI
Ensure the various dtor functions match their prototype and retain their CFI signatures, since they don't have their address taken, they are prone to not getting CFI, making them impossible to call indirectly. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20231215092707.799451071@infradead.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
 Daniel Xu
|
7489723c2e |
bpf: xdp: Register generic_kfunc_set with XDP programs
Registering generic_kfunc_set with XDP programs enables some of the newer BPF features inside XDP -- namely tree based data structures and BPF exceptions. The current motivation for this commit is to enable assertions inside XDP bpf progs. Assertions are a standard and useful tool to encode intent. Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Link: https://lore.kernel.org/r/d07d4614b81ca6aada44fcb89bb6b618fb66e4ca.1702594357.git.dxu@dxuuu.xyz Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
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Andrii Nakryiko
|
4cbb270e11 |
bpf: take into account BPF token when fetching helper protos
Instead of performing unconditional system-wide bpf_capable() and perfmon_capable() calls inside bpf_base_func_proto() function (and other similar ones) to determine eligibility of a given BPF helper for a given program, use previously recorded BPF token during BPF_PROG_LOAD command handling to inform the decision. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231130185229.2688956-8-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Hou Tao
|
169410eba2 |
bpf: Check rcu_read_lock_trace_held() before calling bpf map helpers
These three bpf_map_{lookup,update,delete}_elem() helpers are also
available for sleepable bpf program, so add the corresponding lock
assertion for sleepable bpf program, otherwise the following warning
will be reported when a sleepable bpf program manipulates bpf map under
interpreter mode (aka bpf_jit_enable=0):
WARNING: CPU: 3 PID: 4985 at kernel/bpf/helpers.c:40 ......
CPU: 3 PID: 4985 Comm: test_progs Not tainted 6.6.0+ #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
RIP: 0010:bpf_map_lookup_elem+0x54/0x60
......
Call Trace:
<TASK>
? __warn+0xa5/0x240
? bpf_map_lookup_elem+0x54/0x60
? report_bug+0x1ba/0x1f0
? handle_bug+0x40/0x80
? exc_invalid_op+0x18/0x50
? asm_exc_invalid_op+0x1b/0x20
? __pfx_bpf_map_lookup_elem+0x10/0x10
? rcu_lockdep_current_cpu_online+0x65/0xb0
? rcu_is_watching+0x23/0x50
? bpf_map_lookup_elem+0x54/0x60
? __pfx_bpf_map_lookup_elem+0x10/0x10
___bpf_prog_run+0x513/0x3b70
__bpf_prog_run32+0x9d/0xd0
? __bpf_prog_enter_sleepable_recur+0xad/0x120
? __bpf_prog_enter_sleepable_recur+0x3e/0x120
bpf_trampoline_6442580665+0x4d/0x1000
__x64_sys_getpgid+0x5/0x30
? do_syscall_64+0x36/0xb0
entry_SYSCALL_64_after_hwframe+0x6e/0x76
</TASK>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231204140425.1480317-2-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
 Yafang Shao
|
fe977716b4 |
bpf: Add a new kfunc for cgroup1 hierarchy
A new kfunc is added to acquire cgroup1 of a task: - bpf_task_get_cgroup1 Acquires the associated cgroup of a task whithin a specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID. This new kfunc enables the tracing of tasks within a designated container or cgroup directory in BPF programs. Suggested-by: Tejun Heo <tj@kernel.org> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20231111090034.4248-2-laoar.shao@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
 Dave Marchevsky
|
649924b76a |
bpf: Use bpf_mem_free_rcu when bpf_obj_dropping non-refcounted nodes
The use of bpf_mem_free_rcu to free refcounted local kptrs was added
in commit
|
||
|
Dave Marchevsky
|
1500a5d9f4 |
bpf: Add KF_RCU flag to bpf_refcount_acquire_impl
Refcounted local kptrs are kptrs to user-defined types with a bpf_refcount field. Recent commits ([0], [1]) modified the lifetime of refcounted local kptrs such that the underlying memory is not reused until RCU grace period has elapsed. Separately, verification of bpf_refcount_acquire calls currently succeeds for MAYBE_NULL non-owning reference input, which is a problem as bpf_refcount_acquire_impl has no handling for this case. This patch takes advantage of aforementioned lifetime changes to tag bpf_refcount_acquire_impl kfunc KF_RCU, thereby preventing MAYBE_NULL input to the kfunc. The KF_RCU flag applies to all kfunc params; it's fine for it to apply to the void *meta__ign param as that's populated by the verifier and is tagged __ign regardless. [0]: commit |
||
 Song Liu
|
74523c06ae |
bpf: Add __bpf_dynptr_data* for in kernel use
Different types of bpf dynptr have different internal data storage. Specifically, SKB and XDP type of dynptr may have non-continuous data. Therefore, it is not always safe to directly access dynptr->data. Add __bpf_dynptr_data and __bpf_dynptr_data_rw to replace direct access to dynptr->data. Update bpf_verify_pkcs7_signature to use __bpf_dynptr_data instead of dynptr->data. Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev> Link: https://lore.kernel.org/bpf/20231107045725.2278852-2-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Hou Tao
|
fd381ce60a |
bpf: Check map->usercnt after timer->timer is assigned
When there are concurrent uref release and bpf timer init operations,
the following sequence diagram is possible. It will break the guarantee
provided by bpf_timer: bpf_timer will still be alive after userspace
application releases or unpins the map. It also will lead to kmemleak
for old kernel version which doesn't release bpf_timer when map is
released.
bpf program X:
bpf_timer_init()
lock timer->lock
read timer->timer as NULL
read map->usercnt != 0
process Y:
close(map_fd)
// put last uref
bpf_map_put_uref()
atomic_dec_and_test(map->usercnt)
array_map_free_timers()
bpf_timer_cancel_and_free()
// just return
read timer->timer is NULL
t = bpf_map_kmalloc_node()
timer->timer = t
unlock timer->lock
Fix the problem by checking map->usercnt after timer->timer is assigned,
so when there are concurrent uref release and bpf timer init, either
bpf_timer_cancel_and_free() from uref release reads a no-NULL timer
or the newly-added atomic64_read() returns a zero usercnt.
Because atomic_dec_and_test(map->usercnt) and READ_ONCE(timer->timer)
in bpf_timer_cancel_and_free() are not protected by a lock, so add
a memory barrier to guarantee the order between map->usercnt and
timer->timer. Also use WRITE_ONCE(timer->timer, x) to match the lockless
read of timer->timer in bpf_timer_cancel_and_free().
Reported-by: Hsin-Wei Hung <hsinweih@uci.edu>
Closes: https://lore.kernel.org/bpf/CABcoxUaT2k9hWsS1tNgXyoU3E-=PuOgMn737qK984fbFmfYixQ@mail.gmail.com
Fixes:
|
||
|
Dave Marchevsky
|
391145ba2a |
bpf: Add __bpf_kfunc_{start,end}_defs macros
BPF kfuncs are meant to be called from BPF programs. Accordingly, most
kfuncs are not called from anywhere in the kernel, which the
-Wmissing-prototypes warning is unhappy about. We've peppered
__diag_ignore_all("-Wmissing-prototypes", ... everywhere kfuncs are
defined in the codebase to suppress this warning.
This patch adds two macros meant to bound one or many kfunc definitions.
All existing kfunc definitions which use these __diag calls to suppress
-Wmissing-prototypes are migrated to use the newly-introduced macros.
A new __diag_ignore_all - for "-Wmissing-declarations" - is added to the
__bpf_kfunc_start_defs macro based on feedback from Andrii on an earlier
version of this patch [0] and another recent mailing list thread [1].
In the future we might need to ignore different warnings or do other
kfunc-specific things. This change will make it easier to make such
modifications for all kfunc defs.
[0]: https://lore.kernel.org/bpf/CAEf4BzaE5dRWtK6RPLnjTW-MW9sx9K3Fn6uwqCTChK2Dcb1Xig@mail.gmail.com/
[1]: https://lore.kernel.org/bpf/ZT+2qCc%2FaXep0%2FLf@krava/
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20231031215625.2343848-1-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
 Matthieu Baerts
|
05670f81d1 |
bpf: fix compilation error without CGROUPS
Our MPTCP CI complained [1] -- and KBuild too -- that it was no longer
possible to build the kernel without CONFIG_CGROUPS:
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_new':
kernel/bpf/task_iter.c:919:14: error: 'CSS_TASK_ITER_PROCS' undeclared (first use in this function)
919 | case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
| ^~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c:919:14: note: each undeclared identifier is reported only once for each function it appears in
kernel/bpf/task_iter.c:919:36: error: 'CSS_TASK_ITER_THREADED' undeclared (first use in this function)
919 | case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
| ^~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c:927:60: error: invalid application of 'sizeof' to incomplete type 'struct css_task_iter'
927 | kit->css_it = bpf_mem_alloc(&bpf_global_ma, sizeof(struct css_task_iter));
| ^~~~~~
kernel/bpf/task_iter.c:930:9: error: implicit declaration of function 'css_task_iter_start'; did you mean 'task_seq_start'? [-Werror=implicit-function-declaration]
930 | css_task_iter_start(css, flags, kit->css_it);
| ^~~~~~~~~~~~~~~~~~~
| task_seq_start
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_next':
kernel/bpf/task_iter.c:940:16: error: implicit declaration of function 'css_task_iter_next'; did you mean 'class_dev_iter_next'? [-Werror=implicit-function-declaration]
940 | return css_task_iter_next(kit->css_it);
| ^~~~~~~~~~~~~~~~~~
| class_dev_iter_next
kernel/bpf/task_iter.c:940:16: error: returning 'int' from a function with return type 'struct task_struct *' makes pointer from integer without a cast [-Werror=int-conversion]
940 | return css_task_iter_next(kit->css_it);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_destroy':
kernel/bpf/task_iter.c:949:9: error: implicit declaration of function 'css_task_iter_end' [-Werror=implicit-function-declaration]
949 | css_task_iter_end(kit->css_it);
| ^~~~~~~~~~~~~~~~~
This patch simply surrounds with a #ifdef the new code requiring CGroups
support. It seems enough for the compiler and this is similar to
bpf_iter_css_{new,next,destroy}() functions where no other #ifdef have
been added in kernel/bpf/helpers.c and in the selftests.
Fixes:
|
||
|
Hou Tao
|
e383a45902 |
bpf: Use bpf_global_percpu_ma for per-cpu kptr in __bpf_obj_drop_impl()
The following warning was reported when running "./test_progs -t test_bpf_ma/percpu_free_through_map_free": ------------[ cut here ]------------ WARNING: CPU: 1 PID: 68 at kernel/bpf/memalloc.c:342 CPU: 1 PID: 68 Comm: kworker/u16:2 Not tainted 6.6.0-rc2+ #222 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Workqueue: events_unbound bpf_map_free_deferred RIP: 0010:bpf_mem_refill+0x21c/0x2a0 ...... Call Trace: <IRQ> ? bpf_mem_refill+0x21c/0x2a0 irq_work_single+0x27/0x70 irq_work_run_list+0x2a/0x40 irq_work_run+0x18/0x40 __sysvec_irq_work+0x1c/0xc0 sysvec_irq_work+0x73/0x90 </IRQ> <TASK> asm_sysvec_irq_work+0x1b/0x20 RIP: 0010:unit_free+0x50/0x80 ...... bpf_mem_free+0x46/0x60 __bpf_obj_drop_impl+0x40/0x90 bpf_obj_free_fields+0x17d/0x1a0 array_map_free+0x6b/0x170 bpf_map_free_deferred+0x54/0xa0 process_scheduled_works+0xba/0x370 worker_thread+0x16d/0x2e0 kthread+0x105/0x140 ret_from_fork+0x39/0x60 ret_from_fork_asm+0x1b/0x30 </TASK> ---[ end trace 0000000000000000 ]--- The reason is simple: __bpf_obj_drop_impl() does not know the freeing field is a per-cpu pointer and it uses bpf_global_ma to free the pointer. Because bpf_global_ma is not a per-cpu allocator, so ksize() is used to select the corresponding cache. The bpf_mem_cache with 16-bytes unit_size will always be selected to do the unmatched free and it will trigger the warning in free_bulk() eventually. Because per-cpu kptr doesn't support list or rb-tree now, so fix the problem by only checking whether or not the type of kptr is per-cpu in bpf_obj_free_fields(), and using bpf_global_percpu_ma to these kptrs. Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20231020133202.4043247-7-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Hou Tao
|
e581a3461d |
bpf: Move the declaration of __bpf_obj_drop_impl() to bpf.h
both syscall.c and helpers.c have the declaration of __bpf_obj_drop_impl(), so just move it to a common header file. Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20231020133202.4043247-6-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
 Chuyi Zhou
|
dfab99df14 |
bpf: teach the verifier to enforce css_iter and task_iter in RCU CS
css_iter and task_iter should be used in rcu section. Specifically, in sleepable progs explicit bpf_rcu_read_lock() is needed before use these iters. In normal bpf progs that have implicit rcu_read_lock(), it's OK to use them directly. This patch adds a new a KF flag KF_RCU_PROTECTED for bpf_iter_task_new and bpf_iter_css_new. It means the kfunc should be used in RCU CS. We check whether we are in rcu cs before we want to invoke this kfunc. If the rcu protection is guaranteed, we would let st->type = PTR_TO_STACK | MEM_RCU. Once user do rcu_unlock during the iteration, state MEM_RCU of regs would be cleared. is_iter_reg_valid_init() will reject if reg->type is UNTRUSTED. It is worth noting that currently, bpf_rcu_read_unlock does not clear the state of the STACK_ITER reg, since bpf_for_each_spilled_reg only considers STACK_SPILL. This patch also let bpf_for_each_spilled_reg search STACK_ITER. Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231018061746.111364-6-zhouchuyi@bytedance.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Chuyi Zhou
|
7251d0905e |
bpf: Introduce css open-coded iterator kfuncs
This Patch adds kfuncs bpf_iter_css_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_css in open-coded iterator
style. These kfuncs actually wrapps css_next_descendant_{pre, post}.
css_iter can be used to:
1) iterating a sepcific cgroup tree with pre/post/up order
2) iterating cgroup_subsystem in BPF Prog, like
for_each_mem_cgroup_tree/cpuset_for_each_descendant_pre in kernel.
The API design is consistent with cgroup_iter. bpf_iter_css_new accepts
parameters defining iteration order and starting css. Here we also reuse
BPF_CGROUP_ITER_DESCENDANTS_PRE, BPF_CGROUP_ITER_DESCENDANTS_POST,
BPF_CGROUP_ITER_ANCESTORS_UP enums.
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-5-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Chuyi Zhou
|
c68a78ffe2 |
bpf: Introduce task open coded iterator kfuncs
This patch adds kfuncs bpf_iter_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_task in open-coded iterator
style. BPF programs can use these kfuncs or through bpf_for_each macro to
iterate all processes in the system.
The API design keep consistent with SEC("iter/task"). bpf_iter_task_new()
accepts a specific task and iterating type which allows:
1. iterating all process in the system (BPF_TASK_ITER_ALL_PROCS)
2. iterating all threads in the system (BPF_TASK_ITER_ALL_THREADS)
3. iterating all threads of a specific task (BPF_TASK_ITER_PROC_THREADS)
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Link: https://lore.kernel.org/r/20231018061746.111364-4-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Chuyi Zhou
|
9c66dc94b6 |
bpf: Introduce css_task open-coded iterator kfuncs
This patch adds kfuncs bpf_iter_css_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_css_task in open-coded
iterator style. These kfuncs actually wrapps css_task_iter_{start,next,
end}. BPF programs can use these kfuncs through bpf_for_each macro for
iteration of all tasks under a css.
css_task_iter_*() would try to get the global spin-lock *css_set_lock*, so
the bpf side has to be careful in where it allows to use this iter.
Currently we only allow it in bpf_lsm and bpf iter-s.
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-3-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Yafang Shao
|
29a7e00ffa |
bpf: Fix missed rcu read lock in bpf_task_under_cgroup()
When employed within a sleepable program not under RCU protection, the
use of 'bpf_task_under_cgroup()' may trigger a warning in the kernel log,
particularly when CONFIG_PROVE_RCU is enabled:
[ 1259.662357] WARNING: suspicious RCU usage
[ 1259.662358] 6.5.0+ #33 Not tainted
[ 1259.662360] -----------------------------
[ 1259.662361] include/linux/cgroup.h:423 suspicious rcu_dereference_check() usage!
Other info that might help to debug this:
[ 1259.662366] rcu_scheduler_active = 2, debug_locks = 1
[ 1259.662368] 1 lock held by trace/72954:
[ 1259.662369] #0: ffffffffb5e3eda0 (rcu_read_lock_trace){....}-{0:0}, at: __bpf_prog_enter_sleepable+0x0/0xb0
Stack backtrace:
[ 1259.662385] CPU: 50 PID: 72954 Comm: trace Kdump: loaded Not tainted 6.5.0+ #33
[ 1259.662391] Call Trace:
[ 1259.662393] <TASK>
[ 1259.662395] dump_stack_lvl+0x6e/0x90
[ 1259.662401] dump_stack+0x10/0x20
[ 1259.662404] lockdep_rcu_suspicious+0x163/0x1b0
[ 1259.662412] task_css_set.part.0+0x23/0x30
[ 1259.662417] bpf_task_under_cgroup+0xe7/0xf0
[ 1259.662422] bpf_prog_7fffba481a3bcf88_lsm_run+0x5c/0x93
[ 1259.662431] bpf_trampoline_6442505574+0x60/0x1000
[ 1259.662439] bpf_lsm_bpf+0x5/0x20
[ 1259.662443] ? security_bpf+0x32/0x50
[ 1259.662452] __sys_bpf+0xe6/0xdd0
[ 1259.662463] __x64_sys_bpf+0x1a/0x30
[ 1259.662467] do_syscall_64+0x38/0x90
[ 1259.662472] entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[ 1259.662479] RIP: 0033:0x7f487baf8e29
[...]
[ 1259.662504] </TASK>
This issue can be reproduced by executing a straightforward program, as
demonstrated below:
SEC("lsm.s/bpf")
int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
{
struct cgroup *cgrp = NULL;
struct task_struct *task;
int ret = 0;
if (cmd != BPF_LINK_CREATE)
return 0;
// The cgroup2 should be mounted first
cgrp = bpf_cgroup_from_id(1);
if (!cgrp)
goto out;
task = bpf_get_current_task_btf();
if (bpf_task_under_cgroup(task, cgrp))
ret = -1;
bpf_cgroup_release(cgrp);
out:
return ret;
}
After running the program, if you subsequently execute another BPF program,
you will encounter the warning.
It's worth noting that task_under_cgroup_hierarchy() is also utilized by
bpf_current_task_under_cgroup(). However, bpf_current_task_under_cgroup()
doesn't exhibit this issue because it cannot be used in sleepable BPF
programs.
Fixes:
|
||
|
Dave Marchevsky
|
4ac4546821 |
bpf: Introduce task_vma open-coded iterator kfuncs
This patch adds kfuncs bpf_iter_task_vma_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_task_vma in open-coded
iterator style. BPF programs can use these kfuncs directly or through
bpf_for_each macro for natural-looking iteration of all task vmas.
The implementation borrows heavily from bpf_find_vma helper's locking -
differing only in that it holds the mmap_read lock for all iterations
while the helper only executes its provided callback on a maximum of 1
vma. Aside from locking, struct vma_iterator and vma_next do all the
heavy lifting.
A pointer to an inner data struct, struct bpf_iter_task_vma_data, is the
only field in struct bpf_iter_task_vma. This is because the inner data
struct contains a struct vma_iterator (not ptr), whose size is likely to
change under us. If bpf_iter_task_vma_kern contained vma_iterator directly
such a change would require change in opaque bpf_iter_task_vma struct's
size. So better to allocate vma_iterator using BPF allocator, and since
that alloc must already succeed, might as well allocate all iter fields,
thereby freezing struct bpf_iter_task_vma size.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231013204426.1074286-4-davemarchevsky@fb.com
|
||
 David Vernet
|
d6247ecb6c |
bpf: Add ability to pin bpf timer to calling CPU
BPF supports creating high resolution timers using bpf_timer_* helper functions. Currently, only the BPF_F_TIMER_ABS flag is supported, which specifies that the timeout should be interpreted as absolute time. It would also be useful to be able to pin that timer to a core. For example, if you wanted to make a subset of cores run without timer interrupts, and only have the timer be invoked on a single core. This patch adds support for this with a new BPF_F_TIMER_CPU_PIN flag. When specified, the HRTIMER_MODE_PINNED flag is passed to hrtimer_start(). A subsequent patch will update selftests to validate. Signed-off-by: David Vernet <void@manifault.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Song Liu <song@kernel.org> Acked-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/bpf/20231004162339.200702-2-void@manifault.com |
||
|
Kumar Kartikeya Dwivedi
|
7d3460632d |
bpf: Fix bpf_throw warning on 32-bit arch
On 32-bit architectures, the pointer width is 32-bit, while we try to
cast from a u64 down to it, the compiler complains on mismatch in
integer size. Fix this by first casting to long which should match
the pointer width on targets supported by Linux.
Fixes:
|
||
|
Kumar Kartikeya Dwivedi
|
fd548e1a46 |
bpf: Disallow fentry/fexit/freplace for exception callbacks
During testing, it was discovered that extensions to exception callbacks had no checks, upon running a testcase, the kernel ended up running off the end of a program having final call as bpf_throw, and hitting int3 instructions. The reason is that while the default exception callback would have reset the stack frame to return back to the main program's caller, the replacing extension program will simply return back to bpf_throw, which will instead return back to the program and the program will continue execution, now in an undefined state where anything could happen. The way to support extensions to an exception callback would be to mark the BPF_PROG_TYPE_EXT main subprog as an exception_cb, and prevent it from calling bpf_throw. This would make the JIT produce a prologue that restores saved registers and reset the stack frame. But let's not do that until there is a concrete use case for this, and simply disallow this for now. Similar issues will exist for fentry and fexit cases, where trampoline saves data on the stack when invoking exception callback, which however will then end up resetting the stack frame, and on return, the fexit program will never will invoked as the return address points to the main program's caller in the kernel. Instead of additional complexity and back and forth between the two stacks to enable such a use case, simply forbid it. One key point here to note is that currently X86_TAIL_CALL_OFFSET didn't require any modifications, even though we emit instructions before the corresponding endbr64 instruction. This is because we ensure that a main subprog never serves as an exception callback, and therefore the exception callback (which will be a global subprog) can never serve as the tail call target, eliminating any discrepancies. However, once we support a BPF_PROG_TYPE_EXT to also act as an exception callback, it will end up requiring change to the tail call offset to account for the extra instructions. For simplicitly, tail calls could be disabled for such targets. Noting the above, it appears better to wait for a concrete use case before choosing to permit extension programs to replace exception callbacks. As a precaution, we disable fentry and fexit for exception callbacks as well. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-13-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
ec5290a178 |
bpf: Prevent KASAN false positive with bpf_throw
The KASAN stack instrumentation when CONFIG_KASAN_STACK is true poisons the stack of a function when it is entered and unpoisons it when leaving. However, in the case of bpf_throw, we will never return as we switch our stack frame to the BPF exception callback. Later, this discrepancy will lead to confusing KASAN splats when kernel resumes execution on return from the BPF program. Fix this by unpoisoning everything below the stack pointer of the BPF program, which should cover the range that would not be unpoisoned. An example splat is below: BUG: KASAN: stack-out-of-bounds in stack_trace_consume_entry+0x14e/0x170 Write of size 8 at addr ffffc900013af958 by task test_progs/227 CPU: 0 PID: 227 Comm: test_progs Not tainted 6.5.0-rc2-g43f1c6c9052a-dirty #26 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-2.fc39 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x4a/0x80 print_report+0xcf/0x670 ? arch_stack_walk+0x79/0x100 kasan_report+0xda/0x110 ? stack_trace_consume_entry+0x14e/0x170 ? stack_trace_consume_entry+0x14e/0x170 ? __pfx_stack_trace_consume_entry+0x10/0x10 stack_trace_consume_entry+0x14e/0x170 ? __sys_bpf+0xf2e/0x41b0 arch_stack_walk+0x8b/0x100 ? __sys_bpf+0xf2e/0x41b0 ? bpf_prog_test_run_skb+0x341/0x1c70 ? bpf_prog_test_run_skb+0x341/0x1c70 stack_trace_save+0x9b/0xd0 ? __pfx_stack_trace_save+0x10/0x10 ? __kasan_slab_free+0x109/0x180 ? bpf_prog_test_run_skb+0x341/0x1c70 ? __sys_bpf+0xf2e/0x41b0 ? __x64_sys_bpf+0x78/0xc0 ? do_syscall_64+0x3c/0x90 ? entry_SYSCALL_64_after_hwframe+0x6e/0xd8 kasan_save_stack+0x33/0x60 ? kasan_save_stack+0x33/0x60 ? kasan_set_track+0x25/0x30 ? kasan_save_free_info+0x2b/0x50 ? __kasan_slab_free+0x109/0x180 ? kmem_cache_free+0x191/0x460 ? bpf_prog_test_run_skb+0x341/0x1c70 kasan_set_track+0x25/0x30 kasan_save_free_info+0x2b/0x50 __kasan_slab_free+0x109/0x180 kmem_cache_free+0x191/0x460 bpf_prog_test_run_skb+0x341/0x1c70 ? __pfx_bpf_prog_test_run_skb+0x10/0x10 ? __fget_light+0x51/0x220 __sys_bpf+0xf2e/0x41b0 ? __might_fault+0xa2/0x170 ? __pfx___sys_bpf+0x10/0x10 ? lock_release+0x1de/0x620 ? __might_fault+0xcd/0x170 ? __pfx_lock_release+0x10/0x10 ? __pfx_blkcg_maybe_throttle_current+0x10/0x10 __x64_sys_bpf+0x78/0xc0 ? syscall_enter_from_user_mode+0x20/0x50 do_syscall_64+0x3c/0x90 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 RIP: 0033:0x7f0fbb38880d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f3 45 12 00 f7 d8 64 89 01 48 RSP: 002b:00007ffe13907de8 EFLAGS: 00000206 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007ffe13908708 RCX: 00007f0fbb38880d RDX: 0000000000000050 RSI: 00007ffe13907e20 RDI: 000000000000000a RBP: 00007ffe13907e00 R08: 0000000000000000 R09: 00007ffe13907e20 R10: 0000000000000064 R11: 0000000000000206 R12: 0000000000000003 R13: 0000000000000000 R14: 00007f0fbb532000 R15: 0000000000cfbd90 </TASK> The buggy address belongs to stack of task test_progs/227 KASAN internal error: frame info validation failed; invalid marker: 0 The buggy address belongs to the virtual mapping at [ffffc900013a8000, ffffc900013b1000) created by: kernel_clone+0xcd/0x600 The buggy address belongs to the physical page: page:00000000b70f4332 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11418f flags: 0x2fffe0000000000(node=0|zone=2|lastcpupid=0x7fff) page_type: 0xffffffff() raw: 02fffe0000000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffffc900013af800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffc900013af880: 00 00 00 f1 f1 f1 f1 00 00 00 f3 f3 f3 f3 f3 00 >ffffc900013af900: 00 00 00 00 00 00 00 00 00 00 00 f1 00 00 00 00 ^ ffffc900013af980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffc900013afa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== Disabling lock debugging due to kernel taint Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Acked-by: Andrey Konovalov <andreyknvl@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-11-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Kumar Kartikeya Dwivedi
|
f18b03faba |
bpf: Implement BPF exceptions
This patch implements BPF exceptions, and introduces a bpf_throw kfunc to allow programs to throw exceptions during their execution at runtime. A bpf_throw invocation is treated as an immediate termination of the program, returning back to its caller within the kernel, unwinding all stack frames. This allows the program to simplify its implementation, by testing for runtime conditions which the verifier has no visibility into, and assert that they are true. In case they are not, the program can simply throw an exception from the other branch. BPF exceptions are explicitly *NOT* an unlikely slowpath error handling primitive, and this objective has guided design choices of the implementation of the them within the kernel (with the bulk of the cost for unwinding the stack offloaded to the bpf_throw kfunc). The implementation of this mechanism requires use of add_hidden_subprog mechanism introduced in the previous patch, which generates a couple of instructions to move R1 to R0 and exit. The JIT then rewrites the prologue of this subprog to take the stack pointer and frame pointer as inputs and reset the stack frame, popping all callee-saved registers saved by the main subprog. The bpf_throw function then walks the stack at runtime, and invokes this exception subprog with the stack and frame pointers as parameters. Reviewers must take note that currently the main program is made to save all callee-saved registers on x86_64 during entry into the program. This is because we must do an equivalent of a lightweight context switch when unwinding the stack, therefore we need the callee-saved registers of the caller of the BPF program to be able to return with a sane state. Note that we have to additionally handle r12, even though it is not used by the program, because when throwing the exception the program makes an entry into the kernel which could clobber r12 after saving it on the stack. To be able to preserve the value we received on program entry, we push r12 and restore it from the generated subprogram when unwinding the stack. For now, bpf_throw invocation fails when lingering resources or locks exist in that path of the program. In a future followup, bpf_throw will be extended to perform frame-by-frame unwinding to release lingering resources for each stack frame, removing this limitation. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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|
Yonghong Song
|
36d8bdf75a |
bpf: Add alloc/xchg/direct_access support for local percpu kptr
Add two new kfunc's, bpf_percpu_obj_new_impl() and
bpf_percpu_obj_drop_impl(), to allocate a percpu obj.
Two functions are very similar to bpf_obj_new_impl()
and bpf_obj_drop_impl(). The major difference is related
to percpu handling.
bpf_rcu_read_lock()
struct val_t __percpu_kptr *v = map_val->percpu_data;
...
bpf_rcu_read_unlock()
For a percpu data map_val like above 'v', the reg->type
is set as
PTR_TO_BTF_ID | MEM_PERCPU | MEM_RCU
if inside rcu critical section.
MEM_RCU marking here is similar to NON_OWN_REF as 'v'
is not a owning reference. But NON_OWN_REF is
trusted and typically inside the spinlock while
MEM_RCU is under rcu read lock. RCU is preferred here
since percpu data structures mean potential concurrent
access into its contents.
Also, bpf_percpu_obj_new_impl() is restricted such that
no pointers or special fields are allowed. Therefore,
the bpf_list_head and bpf_rb_root will not be supported
in this patch set to avoid potential memory leak issue
due to racing between bpf_obj_free_fields() and another
bpf_kptr_xchg() moving an allocated object to
bpf_list_head and bpf_rb_root.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230827152744.1996739-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Dave Marchevsky
|
5861d1e8db |
bpf: Allow bpf_spin_{lock,unlock} in sleepable progs
Commit
|
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|
Dave Marchevsky
|
7e26cd12ad |
bpf: Use bpf_mem_free_rcu when bpf_obj_dropping refcounted nodes
This is the final fix for the use-after-free scenario described in
commit
|
||
 Kui-Feng Lee
|
5426700e68 |
bpf: fix bpf_dynptr_slice() to stop return an ERR_PTR.
Verify if the pointer obtained from bpf_xdp_pointer() is either an error or
NULL before returning it.
The function bpf_dynptr_slice() mistakenly returned an ERR_PTR. Instead of
solely checking for NULL, it should also verify if the pointer returned by
bpf_xdp_pointer() is an error or NULL.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/bpf/d1360219-85c3-4a03-9449-253ea905f9d1@moroto.mountain/
Fixes:
|
||
 Alexei Starovoitov
|
6f5a630d7c |
bpf, net: Introduce skb_pointer_if_linear().
Network drivers always call skb_header_pointer() with non-null buffer. Remove !buffer check to prevent accidental misuse of skb_header_pointer(). Introduce skb_pointer_if_linear() instead. Reported-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Jakub Kicinski <kuba@kernel.org> Link: https://lore.kernel.org/r/20230718234021.43640-1-alexei.starovoitov@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Dave Marchevsky
|
c3c510ce43 |
bpf: Add 'owner' field to bpf_{list,rb}_node
As described by Kumar in [0], in shared ownership scenarios it is
necessary to do runtime tracking of {rb,list} node ownership - and
synchronize updates using this ownership information - in order to
prevent races. This patch adds an 'owner' field to struct bpf_list_node
and bpf_rb_node to implement such runtime tracking.
The owner field is a void * that describes the ownership state of a
node. It can have the following values:
NULL - the node is not owned by any data structure
BPF_PTR_POISON - the node is in the process of being added to a data
structure
ptr_to_root - the pointee is a data structure 'root'
(bpf_rb_root / bpf_list_head) which owns this node
The field is initially NULL (set by bpf_obj_init_field default behavior)
and transitions states in the following sequence:
Insertion: NULL -> BPF_PTR_POISON -> ptr_to_root
Removal: ptr_to_root -> NULL
Before a node has been successfully inserted, it is not protected by any
root's lock, and therefore two programs can attempt to add the same node
to different roots simultaneously. For this reason the intermediate
BPF_PTR_POISON state is necessary. For removal, the node is protected
by some root's lock so this intermediate hop isn't necessary.
Note that bpf_list_pop_{front,back} helpers don't need to check owner
before removing as the node-to-be-removed is not passed in as input and
is instead taken directly from the list. Do the check anyways and
WARN_ON_ONCE in this unexpected scenario.
Selftest changes in this patch are entirely mechanical: some BTF
tests have hardcoded struct sizes for structs that contain
bpf_{list,rb}_node fields, those were adjusted to account for the new
sizes. Selftest additions to validate the owner field are added in a
further patch in the series.
[0]: https://lore.kernel.org/bpf/d7hyspcow5wtjcmw4fugdgyp3fwhljwuscp3xyut5qnwivyeru@ysdq543otzv2
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Suggested-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230718083813.3416104-4-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
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Dave Marchevsky
|
0a1f7bfe35 |
bpf: Introduce internal definitions for UAPI-opaque bpf_{rb,list}_node
Structs bpf_rb_node and bpf_list_node are opaquely defined in
uapi/linux/bpf.h, as BPF program writers are not expected to touch their
fields - nor does the verifier allow them to do so.
Currently these structs are simple wrappers around structs rb_node and
list_head and linked_list / rbtree implementation just casts and passes
to library functions for those data structures. Later patches in this
series, though, will add an "owner" field to bpf_{rb,list}_node, such
that they're not just wrapping an underlying node type. Moreover, the
bpf linked_list and rbtree implementations will deal with these owner
pointers directly in a few different places.
To avoid having to do
void *owner = (void*)bpf_list_node + sizeof(struct list_head)
with opaque UAPI node types, add bpf_{list,rb}_node_kern struct
definitions to internal headers and modify linked_list and rbtree to use
the internal types where appropriate.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230718083813.3416104-3-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
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|
Dave Marchevsky
|
7793fc3bab |
bpf: Make bpf_refcount_acquire fallible for non-owning refs
This patch fixes an incorrect assumption made in the original
bpf_refcount series [0], specifically that the BPF program calling
bpf_refcount_acquire on some node can always guarantee that the node is
alive. In that series, the patch adding failure behavior to rbtree_add
and list_push_{front, back} breaks this assumption for non-owning
references.
Consider the following program:
n = bpf_kptr_xchg(&mapval, NULL);
/* skip error checking */
bpf_spin_lock(&l);
if(bpf_rbtree_add(&t, &n->rb, less)) {
bpf_refcount_acquire(n);
/* Failed to add, do something else with the node */
}
bpf_spin_unlock(&l);
It's incorrect to assume that bpf_refcount_acquire will always succeed in this
scenario. bpf_refcount_acquire is being called in a critical section
here, but the lock being held is associated with rbtree t, which isn't
necessarily the lock associated with the tree that the node is already
in. So after bpf_rbtree_add fails to add the node and calls bpf_obj_drop
in it, the program has no ownership of the node's lifetime. Therefore
the node's refcount can be decr'd to 0 at any time after the failing
rbtree_add. If this happens before the refcount_acquire above, the node
might be free'd, and regardless refcount_acquire will be incrementing a
0 refcount.
Later patches in the series exercise this scenario, resulting in the
expected complaint from the kernel (without this patch's changes):
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 207 at lib/refcount.c:25 refcount_warn_saturate+0xbc/0x110
Modules linked in: bpf_testmod(O)
CPU: 1 PID: 207 Comm: test_progs Tainted: G O 6.3.0-rc7-02231-g723de1a718a2-dirty #371
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:refcount_warn_saturate+0xbc/0x110
Code: 6f 64 f6 02 01 e8 84 a3 5c ff 0f 0b eb 9d 80 3d 5e 64 f6 02 00 75 94 48 c7 c7 e0 13 d2 82 c6 05 4e 64 f6 02 01 e8 64 a3 5c ff <0f> 0b e9 7a ff ff ff 80 3d 38 64 f6 02 00 0f 85 6d ff ff ff 48 c7
RSP: 0018:ffff88810b9179b0 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
RDX: 0000000000000202 RSI: 0000000000000008 RDI: ffffffff857c3680
RBP: ffff88810027d3c0 R08: ffffffff8125f2a4 R09: ffff88810b9176e7
R10: ffffed1021722edc R11: 746e756f63666572 R12: ffff88810027d388
R13: ffff88810027d3c0 R14: ffffc900005fe030 R15: ffffc900005fe048
FS: 00007fee0584a700(0000) GS:ffff88811b280000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005634a96f6c58 CR3: 0000000108ce9002 CR4: 0000000000770ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
bpf_refcount_acquire_impl+0xb5/0xc0
(rest of output snipped)
The patch addresses this by changing bpf_refcount_acquire_impl to use
refcount_inc_not_zero instead of refcount_inc and marking
bpf_refcount_acquire KF_RET_NULL.
For owning references, though, we know the above scenario is not possible
and thus that bpf_refcount_acquire will always succeed. Some verifier
bookkeeping is added to track "is input owning ref?" for bpf_refcount_acquire
calls and return false from is_kfunc_ret_null for bpf_refcount_acquire on
owning refs despite it being marked KF_RET_NULL.
Existing selftests using bpf_refcount_acquire are modified where
necessary to NULL-check its return value.
[0]: https://lore.kernel.org/bpf/20230415201811.343116-1-davemarchevsky@fb.com/
Fixes:
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|
Dave Marchevsky
|
cc0d76cafe |
bpf: Fix __bpf_{list,rbtree}_add's beginning-of-node calculation
Given the pointer to struct bpf_{rb,list}_node within a local kptr and
the byte offset of that field within the kptr struct, the calculation changed
by this patch is meant to find the beginning of the kptr so that it can
be passed to bpf_obj_drop.
Unfortunately instead of doing
ptr_to_kptr = ptr_to_node_field - offset_bytes
the calculation is erroneously doing
ptr_to_ktpr = ptr_to_node_field - (offset_bytes * sizeof(struct bpf_rb_node))
or the bpf_list_node equivalent.
This patch fixes the calculation.
Fixes:
|
||
 Daniel Rosenberg
|
3bda08b636 |
bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)
bpf_dynptr_slice(_rw) uses a user provided buffer if it can not provide a pointer to a block of contiguous memory. This buffer is unused in the case of local dynptrs, and may be unused in other cases as well. There is no need to require the buffer, as the kfunc can just return NULL if it was needed and not provided. This adds another kfunc annotation, __opt, which combines with __sz and __szk to allow the buffer associated with the size to be NULL. If the buffer is NULL, the verifier does not check that the buffer is of sufficient size. Signed-off-by: Daniel Rosenberg <drosen@google.com> Link: https://lore.kernel.org/r/20230506013134.2492210-2-drosen@google.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
 Feng Zhou
|
b5ad4cdc46 |
bpf: Add bpf_task_under_cgroup() kfunc
Add a kfunc that's similar to the bpf_current_task_under_cgroup. The difference is that it is a designated task. When hook sched related functions, sometimes it is necessary to specify a task instead of the current task. Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/r/20230506031545.35991-2-zhoufeng.zf@bytedance.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
 Joanne Koong
|
361f129f3c |
bpf: Add bpf_dynptr_clone
The cloned dynptr will point to the same data as its parent dynptr, with the same type, offset, size and read-only properties. Any writes to a dynptr will be reflected across all instances (by 'instance', this means any dynptrs that point to the same underlying data). Please note that data slice and dynptr invalidations will affect all instances as well. For example, if bpf_dynptr_write() is called on an skb-type dynptr, all data slices of dynptr instances to that skb will be invalidated as well (eg data slices of any clones, parents, grandparents, ...). Another example is if a ringbuf dynptr is submitted, any instance of that dynptr will be invalidated. Changing the view of the dynptr (eg advancing the offset or trimming the size) will only affect that dynptr and not affect any other instances. One example use case where cloning may be helpful is for hashing or iterating through dynptr data. Cloning will allow the user to maintain the original view of the dynptr for future use, while also allowing views to smaller subsets of the data after the offset is advanced or the size is trimmed. Signed-off-by: Joanne Koong <joannelkoong@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20230420071414.570108-5-joannelkoong@gmail.com |
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|
Joanne Koong
|
26662d7347 |
bpf: Add bpf_dynptr_size
bpf_dynptr_size returns the number of usable bytes in a dynptr. Signed-off-by: Joanne Koong <joannelkoong@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20230420071414.570108-4-joannelkoong@gmail.com |