5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Ruth <druth@xxxxxxxxxxxx>
[ Upstream commit d864319871b05fadd153e0aede4811ca7008f5d6 ]
syzbot found hanging tasks waiting on rtnl_lock [1]
A reproducer is available in the syzbot bug.
When a request to add multiple actions with the same index is sent, the
second request will block forever on the first request. This holds
rtnl_lock, and causes tasks to hang.
Return -EAGAIN to prevent infinite looping, while keeping documented
behavior.
[1]
INFO: task kworker/1:0:5088 blocked for more than 143 seconds.
Not tainted 6.9.0-rc4-syzkaller-00173-g3cdb45594619 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:0 state:D stack:23744 pid:5088 tgid:5088 ppid:2 flags:0x00004000
Workqueue: events_power_efficient reg_check_chans_work
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5409 [inline]
__schedule+0xf15/0x5d00 kernel/sched/core.c:6746
__schedule_loop kernel/sched/core.c:6823 [inline]
schedule+0xe7/0x350 kernel/sched/core.c:6838
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6895
__mutex_lock_common kernel/locking/mutex.c:684 [inline]
__mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752
wiphy_lock include/net/cfg80211.h:5953 [inline]
reg_leave_invalid_chans net/wireless/reg.c:2466 [inline]
reg_check_chans_work+0x10a/0x10e0 net/wireless/reg.c:2481
Fixes: 0190c1d452a9 ("net: sched: atomically check-allocate action")
Reported-by: syzbot+b87c222546179f4513a7@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=b87c222546179f4513a7
Signed-off-by: David Ruth <druth@xxxxxxxxxxxx>
Reviewed-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240614190326.1349786-1-druth@xxxxxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/sched/act_api.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 92477d51c49dd..52394e45bac55 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -493,7 +493,6 @@ int tcf_idr_check_alloc(struct tc_action_net *tn, u32 *index,
u32 max;
if (*index) {
-again:
rcu_read_lock();
p = idr_find(&idrinfo->action_idr, *index);
@@ -502,7 +501,7 @@ int tcf_idr_check_alloc(struct tc_action_net *tn, u32 *index,
* index but did not assign the pointer yet.
*/
rcu_read_unlock();
- goto again;
+ return -EAGAIN;
}
if (!p) {
--
2.43.0
