From 8844f97238ca6c1ca92a5d6c69f53efd361a266f Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Mon, 16 Nov 2015 16:25:56 +0100 Subject: [PATCH] af_unix: don't append consumed skbs to sk_receive_queue In case multiple writes to a unix stream socket race we could end up in a situation where we pre-allocate a new skb for use in unix_stream_sendpage but have to free it again in the locked section because another skb has been appended meanwhile, which we must use. Accidentally we didn't clear the pointer after consuming it and so we touched freed memory while appending it to the sk_receive_queue. So, clear the pointer after consuming the skb. This bug has been found with syzkaller (http://github.com/google/syzkaller) by Dmitry Vyukov. Fixes: 869e7c62486e ("net: af_unix: implement stream sendpage support") Reported-by: Dmitry Vyukov Cc: Dmitry Vyukov Cc: Eric Dumazet Signed-off-by: Hannes Frederic Sowa Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/unix/af_unix.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 12b886f07982..a8352db5c5b5 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1800,6 +1800,7 @@ alloc_skb: * this - does no harm */ consume_skb(newskb); + newskb = NULL; } if (skb_append_pagefrags(skb, page, offset, size)) { -- 2.20.1