[ 078/180] net: fix a race in sock_queue_err_skb()

[Willy Tarreau]

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <eric.dumazet@xxxxxxxxx>

[ Upstream commit 110c43304db6f06490961529536c362d9ac5732f ]

As soon as an skb is queued into socket error queue, another thread
can consume it, so we are not allowed to reference skb anymore, or risk
use after free.

Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 net/core/skbuff.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 025f924..72ff527 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2989,6 +2989,8 @@ static void sock_rmem_free(struct sk_buff *skb)
  */
 int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)
 {
+	int len = skb->len;
+
 	if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=
 	    (unsigned)sk->sk_rcvbuf)
 		return -ENOMEM;
@@ -3000,7 +3002,7 @@ int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)
 
 	skb_queue_tail(&sk->sk_error_queue, skb);
 	if (!sock_flag(sk, SOCK_DEAD))
-		sk->sk_data_ready(sk, skb->len);
+		sk->sk_data_ready(sk, len);
 	return 0;
 }
 EXPORT_SYMBOL(sock_queue_err_skb);
-- 
1.7.2.1.45.g54fbc



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