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 locks 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 --- Changes in v2: - Use scoped_guard() instead of rcu_read_lock() as suggested by Peter Zijlstra. - Link to v1: 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 bcb09e011e9e1..7dabbcaf825a0 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);
--- base-commit: d082ecbc71e9e0bf49883ee4afd435a77a5101b6 change-id: 20250117-fix_perf_rcu-2ff93190950a
Best regards,