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authorHerbert Xu <herbert@gondor.apana.org.au>2015-07-13 20:01:42 +0800
committerDavid S. Miller <davem@davemloft.net>2015-07-15 15:59:58 -0700
commit89c22d8c3b278212eef6a8cc66b570bc840a6f5a (patch)
treed98e7f2efe02765d1274d5655cdc38abaeb72bcc /net
parentc9805b9986ed88b7df1b14ea7d538d83f2149cf5 (diff)
downloadop-kernel-dev-89c22d8c3b278212eef6a8cc66b570bc840a6f5a.zip
op-kernel-dev-89c22d8c3b278212eef6a8cc66b570bc840a6f5a.tar.gz
net: Fix skb csum races when peeking
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>
Diffstat (limited to 'net')
-rw-r--r--net/core/datagram.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 4e9a3f6..4967262 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -657,7 +657,8 @@ __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
!skb->csum_complete_sw)
netdev_rx_csum_fault(skb->dev);
}
- skb->csum_valid = !sum;
+ if (!skb_shared(skb))
+ skb->csum_valid = !sum;
return sum;
}
EXPORT_SYMBOL(__skb_checksum_complete_head);
@@ -677,11 +678,13 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb)
netdev_rx_csum_fault(skb->dev);
}
- /* Save full packet checksum */
- skb->csum = csum;
- skb->ip_summed = CHECKSUM_COMPLETE;
- skb->csum_complete_sw = 1;
- skb->csum_valid = !sum;
+ if (!skb_shared(skb)) {
+ /* Save full packet checksum */
+ skb->csum = csum;
+ skb->ip_summed = CHECKSUM_COMPLETE;
+ skb->csum_complete_sw = 1;
+ skb->csum_valid = !sum;
+ }
return sum;
}
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