This is a note to let you know that I've just added the patch titled
net/sched: make psched_mtu() RTNL-less safe
to the 4.19-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-make-psched_mtu-rtnl-less-safe.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 19bfe7281d835cff53c41f2059bbd4222c112960
Author: Pedro Tammela <pctammela@xxxxxxxxxxxx>
Date: Mon Jul 10 23:16:34 2023 -0300
net/sched: make psched_mtu() RTNL-less safe
[ Upstream commit 150e33e62c1fa4af5aaab02776b6c3812711d478 ]
Eric Dumazet says[1]:
-------
Speaking of psched_mtu(), I see that net/sched/sch_pie.c is using it
without holding RTNL, so dev->mtu can be changed underneath.
KCSAN could issue a warning.
-------
Annotate dev->mtu with READ_ONCE() so KCSAN don't issue a warning.
[1] https://lore.kernel.org/all/CANn89iJoJO5VtaJ-2=_d2aOQhb0Xw8iBT_Cxqp2HyuS-zj6azw@xxxxxxxxxxxxxx/
v1 -> v2: Fix commit message
Fixes: d4b36210c2e6 ("net: pkt_sched: PIE AQM scheme")
Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Pedro Tammela <pctammela@xxxxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230711021634.561598-1-pctammela@xxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index e09ea6917c061..83a16f3bd6e6a 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -131,7 +131,7 @@ extern const struct nla_policy rtm_tca_policy[TCA_MAX + 1];
*/
static inline unsigned int psched_mtu(const struct net_device *dev)
{
- return dev->mtu + dev->hard_header_len;
+ return READ_ONCE(dev->mtu) + dev->hard_header_len;
}
static inline struct net *qdisc_net(struct Qdisc *q)
