net: adjust skb->truesize in ___pskb_trim()
authorEric Dumazet <edumazet@google.com>
Wed, 26 Apr 2017 16:07:46 +0000 (09:07 -0700)
committerDavid S. Miller <davem@davemloft.net>
Fri, 28 Apr 2017 20:06:47 +0000 (16:06 -0400)
Andrey found a way to trigger the WARN_ON_ONCE(delta < len) in
skb_try_coalesce() using syzkaller and a filter attached to a TCP
socket.

As we did recently in commit 158f323b9868 ("net: adjust skb->truesize in
pskb_expand_head()") we can adjust skb->truesize from ___pskb_trim(),
via a call to skb_condense().

If all frags were freed, then skb->truesize can be recomputed.

This call can be done if skb is not yet owned, or destructor is
sock_edemux().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/core/skbuff.c

index f86bf69cfb8d8bc17262cdba5d9f57a4726cd476..f1d04592ace02f32efa6e05df89c9a5e0023157f 100644 (file)
@@ -1576,6 +1576,8 @@ done:
                skb_set_tail_pointer(skb, len);
        }
 
+       if (!skb->sk || skb->destructor == sock_edemux)
+               skb_condense(skb);
        return 0;
 }
 EXPORT_SYMBOL(___pskb_trim);