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bpf: put uprobe link's path and task in release callback

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BugLink: https://bugs.launchpad.net/bugs/2065400

commit e9c856cabefb71d47b2eeb197f72c9c88e9b45b0 upstream.

There is no need to delay putting either path or task to deallocation
step. It can be done right after bpf_uprobe_unregister. Between release
and dealloc, there could be still some running BPF programs, but they
don't access either task or path, only data in link->uprobes, so it is
safe to do.

On the other hand, doing path_put() in dealloc callback makes this
dealloc sleepable because path_put() itself might sleep. Which is
problematic due to the need to call uprobe's dealloc through call_rcu(),
which is what is done in the next bug fix patch. So solve the problem by
releasing these resources early.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240328052426.3042617-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>
This commit is contained in:
Andrii Nakryiko
2024-03-27 22:24:25 -07:00
committed by Stefan Bader
parent b16f257cd3
commit ed16d56c7a
1 changed files with 3 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/trace/bpf_trace.c
+3 -3
View File
@@ -3142,6 +3142,9 @@ static void bpf_uprobe_multi_link_release(struct bpf_link *link)
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
if (umulti_link->task)
put_task_struct(umulti_link->task);
path_put(&umulti_link->path);
}
static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
@@ -3149,9 +3152,6 @@ static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
struct bpf_uprobe_multi_link *umulti_link;
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
if (umulti_link->task)
put_task_struct(umulti_link->task);
path_put(&umulti_link->path);
kvfree(umulti_link->uprobes);
kfree(umulti_link);
}