This is a note to let you know that I've just added the patch titled
ip: Fix data-races around sysctl_ip_fwd_use_pmtu.
to the 5.18-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:
ip-fix-data-races-around-sysctl_ip_fwd_use_pmtu.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d751f13df1b6b52737cfb9a617fb8eedb96b7ac9
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date: Wed Jul 13 13:51:53 2022 -0700
ip: Fix data-races around sysctl_ip_fwd_use_pmtu.
[ Upstream commit 60c158dc7b1f0558f6cadd5b50d0386da0000d50 ]
While reading sysctl_ip_fwd_use_pmtu, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.
Fixes: f87c10a8aa1e ("ipv4: introduce ip_dst_mtu_maybe_forward and protect forwarding path against pmtu spoofing")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/net/ip.h b/include/net/ip.h
index 26fffda78cca..05fe313f72fa 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -446,7 +446,7 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
struct net *net = dev_net(dst->dev);
unsigned int mtu;
- if (net->ipv4.sysctl_ip_fwd_use_pmtu ||
+ if (READ_ONCE(net->ipv4.sysctl_ip_fwd_use_pmtu) ||
ip_mtu_locked(dst) ||
!forwarding) {
mtu = rt->rt_pmtu;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index ed01063d8f30..8363e575c455 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1397,7 +1397,7 @@ u32 ip_mtu_from_fib_result(struct fib_result *res, __be32 daddr)
struct fib_info *fi = res->fi;
u32 mtu = 0;
- if (dev_net(dev)->ipv4.sysctl_ip_fwd_use_pmtu ||
+ if (READ_ONCE(dev_net(dev)->ipv4.sysctl_ip_fwd_use_pmtu) ||
fi->fib_metrics->metrics[RTAX_LOCK - 1] & (1 << RTAX_MTU))
mtu = fi->fib_mtu;
