diff options
| author |   Eric Dumazet <edumazet@google.com> | 2017-08-16 11:09:12 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2017-08-16 16:28:47 -0700 |
| commit | c780a049f9bf442314335372c9abc4548bfe3e44 (patch) | |
| tree | 9bfe8c76f75ea6d1dbc52efa95ff294d80d58c8a | |
| parent | ptr_ring: use kmalloc_array() (diff) | |
| download | linux-dev-c780a049f9bf442314335372c9abc4548bfe3e44.tar.xz linux-dev-c780a049f9bf442314335372c9abc4548bfe3e44.zip | |
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>
| -rw-r--r-- | include/net/ip.h | 4 | ||||
| -rw-r--r-- | net/ipv4/route.c | 2 |
2 files changed, 3 insertions, 3 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); 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) |