The commit ee971630f20f ("bpf: Allow some trace helpers for all prog
types") made bpf_get_cgroup_classid_curr helper available to all BPF
program types. This helper used __task_get_classid() which calls
task_cls_state() that requires rcu_read_lock_bh_held().
This triggers an RCU warning when called from BPF syscall programs
which run under rcu_read_lock_trace():
WARNING: suspicious RCU usage
6.15.0-rc4-syzkaller-g079e5c56a5c4 #0 Not tainted
-----------------------------
net/core/netclassid_cgroup.c:24 suspicious rcu_dereference_check() usage!
Fix this by replacing __task_get_classid() with task_cls_classid()
which handles RCU locking internally using regular rcu_read_lock() and
is safe to call from any context.
Reported-by: syzbot+b4169a1cfb945d2ed0ec@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=b4169a1cfb945d2ed0ec
Fixes: ee971630f20f ("bpf: Allow some trace helpers for all prog types")
Signed-off-by: Charalampos Mitrodimas <charmitro@xxxxxxxxxx>
---
net/core/filter.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 30e7d36790883b29174654315738e93237e21dd0..3b3f81cf674dde7d2bd83488450edad4e129bdac 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3083,7 +3083,7 @@ static const struct bpf_func_proto bpf_msg_pop_data_proto = {
#ifdef CONFIG_CGROUP_NET_CLASSID
BPF_CALL_0(bpf_get_cgroup_classid_curr)
{
- return __task_get_classid(current);
+ return task_cls_classid(current);
}
const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto = {
---
base-commit: 079e5c56a5c41d285068939ff7b0041ab10386fa
change-id: 20250608-rcu-fix-task_cls_state-0ed73f437d1e
Best regards,
--
Charalampos Mitrodimas <charmitro@xxxxxxxxxx>
