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ip: Fix data-races around sysctl_ip_fwd_use_pmtu.

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While reading sysctl_ip_fwd_use_pmtu, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

Fixes: f87c10a8aa ("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>
This commit is contained in:
Kuniyuki Iwashima 2022-07-13 13:51:53 -07:00 committed by David S. Miller
parent 0968d2a441
commit 60c158dc7b
2 changed files with 2 additions and 2 deletions
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2
include/net/ip.h
View File

@ -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;

2
net/ipv4/route.c
View File

@ -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;