diff options
authorHerbert Xu <herbert@gondor.apana.org.au>2015-07-13 20:01:42 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-10-01 12:07:36 +0200
commit4164cda8cad7303614d211192d27a912de53a463 (patch)
parent0ba48ae94c393dc4c43b257400046feeeb9c6fad (diff)
net: Fix skb csum races when peeking
[ Upstream commit 89c22d8c3b278212eef6a8cc66b570bc840a6f5a ] When we calculate the checksum on the recv path, we store the result in the skb as an optimisation in case we need the checksum again down the line. This is in fact bogus for the MSG_PEEK case as this is done without any locking. So multiple threads can peek and then store the result to the same skb, potentially resulting in bogus skb states. This patch fixes this by only storing the result if the skb is not shared. This preserves the optimisations for the few cases where it can be done safely due to locking or other reasons, e.g., SIOCINQ. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 2 insertions, 1 deletions
diff --git a/net/core/datagram.c b/net/core/datagram.c
index f1506c7d414e..80b0fd83fac8 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -700,7 +700,8 @@ __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
if (likely(!sum)) {
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
- skb->ip_summed = CHECKSUM_UNNECESSARY;
+ if (!skb_shared(skb))
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
return sum;