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| author | Eric Dumazet <edumazet@google.com> | 2017-08-16 11:09:12 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-08-30 10:26:25 +0200 |
| commit | 9c579acf65228945a02e674f8c5766571a63b51f (patch) | |
| tree | 2ed1f664f55b4d22fd73bb51eb8bfce6b03bfa3f /include | |
| parent | 12ee6d75d6a1e65e902aca105679d46291c16e40 (diff) | |
| download | linux-9c579acf65228945a02e674f8c5766571a63b51f.tar.gz linux-9c579acf65228945a02e674f8c5766571a63b51f.tar.bz2 linux-9c579acf65228945a02e674f8c5766571a63b51f.zip | |
ipv4: better IP_MAX_MTU enforcement
[ Upstream commit c780a049f9bf442314335372c9abc4548bfe3e44 ]
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/ip.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/net/ip.h b/include/net/ip.h index 821cedcc8e73..0cf7f5a65fe6 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -352,7 +352,7 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst, !forwarding) return dst_mtu(dst); - return min(dst->dev->mtu, IP_MAX_MTU); + return min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU); } static inline unsigned int ip_skb_dst_mtu(struct sock *sk, @@ -364,7 +364,7 @@ static inline unsigned int ip_skb_dst_mtu(struct sock *sk, return ip_dst_mtu_maybe_forward(skb_dst(skb), forwarding); } - return min(skb_dst(skb)->dev->mtu, IP_MAX_MTU); + return min(READ_ONCE(skb_dst(skb)->dev->mtu), IP_MAX_MTU); } u32 ip_idents_reserve(u32 hash, int segs); |