[LLC]: Use pskb_trim_rcsum() in llc_fixup_skb().

Kernel Bugzilla #6409

If we use plain skb_trim(), that's wrong, because if
the SKB is cloned, and it can be because we unshared
it in the caller, we have to allow reallocation.  The
pskb_trim*() family of routines is therefore the most
appropriate here.

Signed-off-by: David S. Miller <davem@davemloft.net>

net/llc/llc_input.c

@@ -118,7 +118,8 @@ static inline int llc_fixup_skb(struct sk_buff *skb)
 		u16 pdulen = eth_hdr(skb)->h_proto,
 		    data_size = ntohs(pdulen) - llc_len;
 
-		skb_trim(skb, data_size);
+		if (unlikely(pskb_trim_rcsum(skb, data_size)))
+			return 0;
 	}
 	return 1;
 }