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authorEric Dumazet <edumazet@google.com>2017-08-16 21:09:12 +0300
committerDavid S. Miller <davem@davemloft.net>2017-08-17 02:28:47 +0300
commitc780a049f9bf442314335372c9abc4548bfe3e44 (patch)
tree9bfe8c76f75ea6d1dbc52efa95ff294d80d58c8a /net
parent81fbfe8adaf38d4f5a98c19bebfd41c5d6acaee8 (diff)
downloadlinux-c780a049f9bf442314335372c9abc4548bfe3e44.tar.xz
ipv4: better IP_MAX_MTU enforcement
While working on yet another syzkaller report, I found that our IP_MAX_MTU enforcements were not properly done. gcc seems to reload dev->mtu for min(dev->mtu, IP_MAX_MTU), and final result can be bigger than IP_MAX_MTU :/ This is a problem because device mtu can be changed on other cpus or threads. While this patch does not fix the issue I am working on, it is probably worth addressing it. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/route.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 7effa62beed3..fe877a4a72b1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1267,7 +1267,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst)
if (mtu)
return mtu;
- mtu = dst->dev->mtu;
+ mtu = READ_ONCE(dst->dev->mtu);
if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
if (rt->rt_uses_gateway && mtu > 576)