net: BUG instead of corrupting memory in pskb_expand_head

If the caller of pskb_expand_head specifies a negative nhead
we'll silently overwrite other people's memory.  This patch
makes it BUG instead.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2c218a0808b4..8bd248a64879 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -738,6 +738,8 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 #endif
         long off;
 
+        BUG_ON(nhead < 0);
+
         if (skb_shared(skb))
                 BUG();