From: Kuniyuki Iwashima kuniyu@amazon.com
[ 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@amazon.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/ip.h | 2 +- net/ipv4/route.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/net/ip.h b/include/net/ip.h index 3f3ea86b2173..21fc0a29a8d4 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -442,7 +442,7 @@ 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) return dst_mtu(dst); diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 9280e5087159..7004e379c325 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1423,7 +1423,7 @@ 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;