Patch "net: linkwatch: use system_unbound_wq" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: linkwatch: use system_unbound_wq

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-linkwatch-use-system_unbound_wq.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a7d3abde1a50db7b75376b4ded46ca86318dbb26
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Mon Aug 5 08:58:21 2024 +0000

    net: linkwatch: use system_unbound_wq
    
    [ Upstream commit 3e7917c0cdad835a5121520fc5686d954b7a61ab ]
    
    linkwatch_event() grabs possibly very contended RTNL mutex.
    
    system_wq is not suitable for such work.
    
    Inspired by many noisy syzbot reports.
    
    3 locks held by kworker/0:7/5266:
     #0: ffff888015480948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3206 [inline]
     #0: ffff888015480948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x90a/0x1830 kernel/workqueue.c:3312
     #1: ffffc90003f6fd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3207 [inline]
     , at: process_scheduled_works+0x945/0x1830 kernel/workqueue.c:3312
     #2: ffffffff8fa6f208 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:276
    
    Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Link: https://patch.msgid.link/20240805085821.1616528-1-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 35b0e39030daf..a70b2adc47a16 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -130,9 +130,9 @@ static void linkwatch_schedule_work(int urgent)
 	 * override the existing timer.
 	 */
 	if (test_bit(LW_URGENT, &linkwatch_flags))
-		mod_delayed_work(system_wq, &linkwatch_work, 0);
+		mod_delayed_work(system_unbound_wq, &linkwatch_work, 0);
 	else
-		schedule_delayed_work(&linkwatch_work, delay);
+		queue_delayed_work(system_unbound_wq, &linkwatch_work, delay);
 }