Commit 8844f972 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by David S. Miller

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: 869e7c62 ("net: af_unix: implement stream sendpage support")
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 24cb7055
...@@ -1800,6 +1800,7 @@ static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page, ...@@ -1800,6 +1800,7 @@ static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,
* this - does no harm * this - does no harm
*/ */
consume_skb(newskb); consume_skb(newskb);
newskb = NULL;
} }
if (skb_append_pagefrags(skb, page, offset, size)) { if (skb_append_pagefrags(skb, page, offset, size)) {
......
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