This is a note to let you know that I've just added the patch titled
net: sched: fix use-after-free in taprio_change()
to the 5.15-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-sched-fix-use-after-free-in-taprio_change.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6a3a7d52814a8ccee67d8becc5ae74ecc6f9bdb1
Author: Dmitry Antipov <dmantipov@xxxxxxxxx>
Date: Fri Oct 18 08:13:38 2024 +0300
net: sched: fix use-after-free in taprio_change()
[ Upstream commit f504465970aebb2467da548f7c1efbbf36d0f44b ]
In 'taprio_change()', 'admin' pointer may become dangling due to sched
switch / removal caused by 'advance_sched()', and critical section
protected by 'q->current_entry_lock' is too small to prevent from such
a scenario (which causes use-after-free detected by KASAN). Fix this
by prefer 'rcu_replace_pointer()' over 'rcu_assign_pointer()' to update
'admin' immediately before an attempt to schedule freeing.
Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule")
Reported-by: syzbot+b65e0af58423fc8a73aa@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa
Acked-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
Link: https://patch.msgid.link/20241018051339.418890-1-dmantipov@xxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 49831bd6a37d5..44b971ef343ce 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1612,7 +1612,8 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
taprio_start_sched(sch, start, new_admin);
- rcu_assign_pointer(q->admin_sched, new_admin);
+ admin = rcu_replace_pointer(q->admin_sched, new_admin,
+ lockdep_rtnl_is_held());
if (admin)
call_rcu(&admin->rcu, taprio_free_sched_cb);
