From 3deb12c788c385e17142ce6ec50f769852fcec65 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" Date: Mon, 21 Oct 2024 12:25:26 +0200 Subject: [PATCH 1/2] mptcp: init: protect sched with rcu_read_lock Enabling CONFIG_PROVE_RCU_LIST with its dependence CONFIG_RCU_EXPERT creates this splat when an MPTCP socket is created: ============================= WARNING: suspicious RCU usage 6.12.0-rc2+ #11 Not tainted ----------------------------- net/mptcp/sched.c:44 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 no locks held by mptcp_connect/176. stack backtrace: CPU: 0 UID: 0 PID: 176 Comm: mptcp_connect Not tainted 6.12.0-rc2+ #11 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: dump_stack_lvl (lib/dump_stack.c:123) lockdep_rcu_suspicious (kernel/locking/lockdep.c:6822) mptcp_sched_find (net/mptcp/sched.c:44 (discriminator 7)) mptcp_init_sock (net/mptcp/protocol.c:2867 (discriminator 1)) ? sock_init_data_uid (arch/x86/include/asm/atomic.h:28) inet_create.part.0.constprop.0 (net/ipv4/af_inet.c:386) ? __sock_create (include/linux/rcupdate.h:347 (discriminator 1)) __sock_create (net/socket.c:1576) __sys_socket (net/socket.c:1671) ? __pfx___sys_socket (net/socket.c:1712) ? do_user_addr_fault (arch/x86/mm/fault.c:1419 (discriminator 1)) __x64_sys_socket (net/socket.c:1728) do_syscall_64 (arch/x86/entry/common.c:52 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) That's because when the socket is initialised, rcu_read_lock() is not used despite the explicit comment written above the declaration of mptcp_sched_find() in sched.c. Adding the missing lock/unlock avoids the warning. Fixes: 1730b2b2c5a5 ("mptcp: add sched in mptcp_sock") Cc: stable@vger.kernel.org Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/523 Reviewed-by: Geliang Tang Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Simon Horman Link: https://patch.msgid.link/20241021-net-mptcp-sched-lock-v1-1-637759cf061c@kernel.org Signed-off-by: Jakub Kicinski --- net/mptcp/protocol.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 6d0e201c3eb2..d263091659e0 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2864,8 +2864,10 @@ static int mptcp_init_sock(struct sock *sk) if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net)) return -ENOMEM; + rcu_read_lock(); ret = mptcp_init_sched(mptcp_sk(sk), mptcp_sched_find(mptcp_get_scheduler(net))); + rcu_read_unlock(); if (ret) return ret; From 5513dc1d8fec929006548dde4acdabdc54379beb Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" Date: Mon, 21 Oct 2024 12:25:28 +0200 Subject: [PATCH 2/2] selftests: mptcp: list sysctl data Listing all the values linked to the MPTCP sysctl knobs was not exercised in MPTCP test suite. Let's do that to avoid any regressions, but also to have a kernel with a debug kconfig verifying more assumptions. For the moment, we are not interested by the output, only to avoid crashes and warnings. Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Simon Horman Link: https://patch.msgid.link/20241021-net-mptcp-sched-lock-v1-3-637759cf061c@kernel.org Signed-off-by: Jakub Kicinski --- tools/testing/selftests/net/mptcp/mptcp_connect.sh | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh index 57325d57e4c6..b48b4e56826a 100755 --- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh @@ -259,6 +259,15 @@ check_mptcp_disabled() mptcp_lib_ns_init disabled_ns print_larger_title "New MPTCP socket can be blocked via sysctl" + + # mainly to cover more code + if ! ip netns exec ${disabled_ns} sysctl net.mptcp >/dev/null; then + mptcp_lib_pr_fail "not able to list net.mptcp sysctl knobs" + mptcp_lib_result_fail "not able to list net.mptcp sysctl knobs" + ret=${KSFT_FAIL} + return 1 + fi + # net.mptcp.enabled should be enabled by default if [ "$(ip netns exec ${disabled_ns} sysctl net.mptcp.enabled | awk '{ print $3 }')" -ne 1 ]; then mptcp_lib_pr_fail "net.mptcp.enabled sysctl is not 1 by default"