[PATCH 4.10 107/129] net: adjust skb->truesize in ___pskb_trim()

[Greg Kroah-Hartman]

4.10-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Dumazet <edumazet@xxxxxxxxxx>


[ Upstream commit c21b48cc1bbf2f5af3ef54ada559f7fadf8b508b ]

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@xxxxxxxxxx>
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/skbuff.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1572,6 +1572,8 @@ done:
 		skb_set_tail_pointer(skb, len);
 	}
 
+	if (!skb->sk || skb->destructor == sock_edemux)
+		skb_condense(skb);
 	return 0;
 }
 EXPORT_SYMBOL(___pskb_trim);