[PATCH bpf-next] bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem()

[PATCH bpf-next] bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem()

[Hou Tao]

From: Hou Tao <houtao1@huawei.com>

bpf_map_lookup_percpu_elem() helper is also available for sleepable bpf
program. When BPF JIT is disabled or under 32-bit host,
bpf_map_lookup_percpu_elem() will not be inlined. Using it in a
sleepable bpf program will trigger the warning in
bpf_map_lookup_percpu_elem(), because the bpf program only holds
rcu_read_lock_trace lock. Therefore, add the missed check.

Reported-by: syzbot+dce5aae19ae4d6399986@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000176a130617420310@google.com/
Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 kernel/bpf/helpers.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index c1113b74e1e2..601500786ab4 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -130,7 +130,8 @@ const struct bpf_func_proto bpf_map_peek_elem_proto = {
 
 BPF_CALL_3(bpf_map_lookup_percpu_elem, struct bpf_map *, map, void *, key, u32, cpu)
 {
-	WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
+	WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
+		     !rcu_read_lock_bh_held());
 	return (unsigned long) map->ops->map_lookup_percpu_elem(map, key, cpu);
 }
 
-- 
2.29.2

Re: [PATCH bpf-next] bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon, 26 May 2025 14:25:34 +0800 you wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> bpf_map_lookup_percpu_elem() helper is also available for sleepable bpf
> program. When BPF JIT is disabled or under 32-bit host,
> bpf_map_lookup_percpu_elem() will not be inlined. Using it in a
> sleepable bpf program will trigger the warning in
> bpf_map_lookup_percpu_elem(), because the bpf program only holds
> rcu_read_lock_trace lock. Therefore, add the missed check.
> 
> [...]

Here is the summary with links:
  - [bpf-next] bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem()
    https://git.kernel.org/bpf/bpf-next/c/d4965578267e

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html