path: root/net
diff options
authorEric Dumazet <edumazet@google.com>2013-10-15 11:54:30 -0700
committerDavid S. Miller <davem@davemloft.net>2013-10-17 16:08:08 -0400
commitc52e2421f7368fd36cbe330d2cf41b10452e39a9 (patch)
tree337ead817a96c313068b3d4b0c4f844ef23014f9 /net
parentdf709a18cae475de38ddaff63584692d50267b92 (diff)
tcp: must unclone packets before mangling them
TCP stack should make sure it owns skbs before mangling them. We had various crashes using bnx2x, and it turned out gso_size was cleared right before bnx2x driver was populating TC descriptor of the _previous_ packet send. TCP stack can sometime retransmit packets that are still in Qdisc. Of course we could make bnx2x driver more robust (using ACCESS_ONCE(shinfo->gso_size) for example), but the bug is TCP stack. We have identified two points where skb_unclone() was needed. This patch adds a WARN_ON_ONCE() to warn us if we missed another fix of this kind. Kudos to Neal for finding the root cause of this bug. Its visible using small MSS. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 6 insertions, 3 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index c6f01f2cdb3..8fad1c15568 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -986,6 +986,9 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
unsigned int mss_now)
+ /* Make sure we own this skb before messing gso_size/gso_segs */
+ WARN_ON_ONCE(skb_cloned(skb));
if (skb->len <= mss_now || !sk_can_gso(sk) ||
skb->ip_summed == CHECKSUM_NONE) {
/* Avoid the costly divide in the normal
@@ -1067,9 +1070,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
if (nsize < 0)
nsize = 0;
- if (skb_cloned(skb) &&
- skb_is_nonlinear(skb) &&
- pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+ if (skb_unclone(skb, GFP_ATOMIC))
return -ENOMEM;
/* Get a new skb... force flag on. */
@@ -2344,6 +2345,8 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
int oldpcount = tcp_skb_pcount(skb);
if (unlikely(oldpcount > 1)) {
+ if (skb_unclone(skb, GFP_ATOMIC))
+ return -ENOMEM;
tcp_init_tso_segs(sk, skb, cur_mss);
tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));