From: Eric Dumazet <edumazet@google.com>
Date: Wed, 26 Apr 2017 16:07:46 +0000 (-0700)
Subject: net: adjust skb->truesize in ___pskb_trim()
X-Git-Tag: MMI-PSA29.97-13-9~5767^2~1
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=c21b48cc1bbf2f5af3ef54ada559f7fadf8b508b;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

net: adjust skb->truesize in ___pskb_trim()

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>
---

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..f1d04592ace0 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -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);