From: Kuniyuki Iwashima Date: Wed, 13 Jul 2022 20:51:53 +0000 (-0700) Subject: ip: Fix data-races around sysctl_ip_fwd_use_pmtu. X-Git-Tag: v5.19~46^2~29^2~12 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=60c158dc7b1f0558f6cadd5b50d0386da0000d50;p=mirror_ubuntu-kernels.git ip: Fix data-races around sysctl_ip_fwd_use_pmtu. 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 Signed-off-by: David S. Miller --- 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 356f535f3443..91c4f60de75a 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1398,7 +1398,7 @@ 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;