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@xxxxxxxxxxxxxxx
Fixes: bd2756811766 ("perf: Rewrite core context handling")
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
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@xxxxxxxxxx
---
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,
--
Breno Leitao <leitao@xxxxxxxxxx>
