From 8844f97238ca6c1ca92a5d6c69f53efd361a266f Mon Sep 17 00:00:00 2001
From: Hannes Frederic Sowa <hannes@stressinduktion.org>
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 <dvyukov@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
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 12b886f07982f..a8352db5c5b54 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1800,6 +1800,7 @@ static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,
* this - does no harm
*/
consume_skb(newskb);
+ newskb = NULL;
}
if (skb_append_pagefrags(skb, page, offset, size)) {
--
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