5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Ruth druth@chromium.org
[ 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@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b87c222546179f4513a7 Signed-off-by: David Ruth druth@chromium.org Reviewed-by: Jamal Hadi Salim jhs@mojatatu.com Link: https://lore.kernel.org/r/20240614190326.1349786-1-druth@chromium.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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) {