[PATCH v2] net/sched: act_api: avoid dereferencing ERR_PTR in tcf_idrinfo_destroy

[Shivani Gupta <shivani07g@gmail.com>]

syzbot reported a crash in tc_act_in_hw() during netns teardown where
tcf_idrinfo_destroy() passed an ERR_PTR(-EBUSY) value as a tc_action
pointer, leading to an invalid dereference.

Guard against ERR_PTR entries when iterating the action IDR so teardown
does not call tc_act_in_hw() on an error pointer.

Fixes: 84a7d6797e6a ("net/sched: acp_api: no longer acquire RTNL in tc_action_net_exit()")
Link: https://syzkaller.appspot.com/bug?extid=8f1c492ffa4644ff3826
Reported-by: syzbot+8f1c492ffa4644ff3826@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8f1c492ffa4644ff3826
Signed-off-by: Shivani Gupta <shivani07g@gmail.com>
---
v2:
- Drop WARN_ON_ONCE() as ERR_PTR can be expected in a corner case.
- Add Fixes: tag.

 net/sched/act_api.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index ff6be5cfe2b0..5e0a196ce66a 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -940,6 +940,9 @@ void tcf_idrinfo_destroy(const struct tc_action_ops *ops,
 	int ret;
 
 	idr_for_each_entry_ul(idr, p, tmp, id) {
+		if (IS_ERR(p)) {
+			continue;
+		}
 		if (tc_act_in_hw(p) && !mutex_taken) {
 			rtnl_lock();
 			mutex_taken = true;
-- 
2.34.1