The perf_iterate_ctx() function performs RCU list traversal but currently lacks RCU read lock protection. This causes lockdep warnings when running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y:
WARNING: suspicious RCU usage kernel/events/core.c:8168 RCU-list traversed in non-reader section!!
Call Trace: lockdep_rcu_suspicious ? perf_event_addr_filters_apply perf_iterate_ctx perf_event_exec begin_new_exec ? load_elf_phdrs load_elf_binary ? lock_acquire ? find_held_lock ? bprm_execve bprm_execve do_execveat_common.isra.0 __x64_sys_execve do_syscall_64 entry_SYSCALL_64_after_hwframe
This protection was previously present but was removed in commit bd2756811766 ("perf: Rewrite core context handling"). Add back the necessary rcu_read_lock()/rcu_read_unlock() pair around perf_iterate_ctx() call in perf_event_exec().
CC: stable@vger.kernel.org Fixes: bd2756811766 ("perf: Rewrite core context handling") Signed-off-by: Breno Leitao leitao@debian.org --- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 065f9188b44a0d8ee66cc76314ae247dbe45cb57..e2adb06f8d81307b2762375474bee1c9e8a74598 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8277,7 +8277,9 @@ void perf_event_exec(void)
perf_event_enable_on_exec(ctx); perf_event_remove_on_exec(ctx); + rcu_read_lock(); perf_iterate_ctx(ctx, perf_event_addr_filters_exec, NULL, true); + rcu_read_unlock();
perf_unpin_context(ctx); put_ctx(ctx);
--- base-commit: dbb0aea70ce4b85915a52d7adf9af57bd80f330a change-id: 20250117-fix_perf_rcu-2ff93190950a
Best regards,
On Fri, Jan 17, 2025 at 06:41:07AM -0800, Breno Leitao wrote:
The perf_iterate_ctx() function performs RCU list traversal but currently lacks RCU read lock protection. This causes lockdep warnings when running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y:
WARNING: suspicious RCU usage kernel/events/core.c:8168 RCU-list traversed in non-reader section!!
Call Trace: lockdep_rcu_suspicious ? perf_event_addr_filters_apply perf_iterate_ctx perf_event_exec begin_new_exec ? load_elf_phdrs load_elf_binary ? lock_acquire ? find_held_lock ? bprm_execve bprm_execve do_execveat_common.isra.0 __x64_sys_execve do_syscall_64 entry_SYSCALL_64_after_hwframeThis protection was previously present but was removed in commit bd2756811766 ("perf: Rewrite core context handling"). Add back the necessary rcu_read_lock()/rcu_read_unlock() pair around perf_iterate_ctx() call in perf_event_exec().
Hurm, I think it got ripped out because we no longer need to refer that perf_event_ctxp[].
Anyway, please write it like so:
diff --git a/kernel/events/core.c b/kernel/events/core.c index 0f8c55990783..b77f95089d62 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8320,7 +8320,8 @@ void perf_event_exec(void)
perf_event_enable_on_exec(ctx); perf_event_remove_on_exec(ctx); - perf_iterate_ctx(ctx, perf_event_addr_filters_exec, NULL, true); + scoped_guard(rcu) + perf_iterate_ctx(ctx, perf_event_addr_filters_exec, NULL, true);
perf_unpin_context(ctx); put_ctx(ctx);
The following commit has been merged into the perf/urgent branch of tip:
Commit-ID: 0fe8813baf4b2e865d3b2c735ce1a15b86002c74 Gitweb: https://git.kernel.org/tip/0fe8813baf4b2e865d3b2c735ce1a15b86002c74 Author: Breno Leitao leitao@debian.org AuthorDate: Fri, 17 Jan 2025 06:41:07 -08:00 Committer: Ingo Molnar mingo@kernel.org CommitterDate: Mon, 24 Feb 2025 19:17:04 +01:00
perf/core: Add RCU read lock protection to perf_iterate_ctx()
The perf_iterate_ctx() function performs RCU list traversal but currently lacks RCU read lock protection. This causes lockdep warnings when running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y:
WARNING: suspicious RCU usage kernel/events/core.c:8168 RCU-list traversed in non-reader section!!
Call Trace: lockdep_rcu_suspicious ? perf_event_addr_filters_apply perf_iterate_ctx perf_event_exec begin_new_exec ? load_elf_phdrs load_elf_binary ? lock_acquire ? find_held_lock ? bprm_execve bprm_execve do_execveat_common.isra.0 __x64_sys_execve do_syscall_64 entry_SYSCALL_64_after_hwframe
This protection was previously present but was removed in commit bd2756811766 ("perf: Rewrite core context handling"). Add back the necessary rcu_read_lock()/rcu_read_unlock() pair around perf_iterate_ctx() call in perf_event_exec().
[ mingo: Use scoped_guard() as suggested by Peter ]
Fixes: bd2756811766 ("perf: Rewrite core context handling") Signed-off-by: Breno Leitao leitao@debian.org Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250117-fix_perf_rcu-v1-1-13cb9210fc6a@debian.org --- kernel/events/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index bcb09e0..7dabbca 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8321,7 +8321,8 @@ void perf_event_exec(void)
perf_event_enable_on_exec(ctx); perf_event_remove_on_exec(ctx); - perf_iterate_ctx(ctx, perf_event_addr_filters_exec, NULL, true); + scoped_guard(rcu) + perf_iterate_ctx(ctx, perf_event_addr_filters_exec, NULL, true);
perf_unpin_context(ctx); put_ctx(ctx);
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