[NET]: Warn in __skb_trim if skb is paged

It's better to warn and fail rather than rarely triggering BUG on paths
that incorrectly call skb_trim/__skb_trim on a non-linear skb.

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

1 files changed, 12 insertions, 12 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 830f58fa03a2..93e4db221585 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -975,15 +975,16 @@ static inline void skb_reserve(struct sk_buff *skb, int len)
 #define NET_SKB_PAD     16
 #endif
 
-extern int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc);
+extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);
 
 static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
 {
-        if (!skb->data_len) {
-                skb->len  = len;
-                skb->tail = skb->data + len;
-        } else
-                ___pskb_trim(skb, len, 0);
+        if (unlikely(skb->data_len)) {
+                WARN_ON(1);
+                return;
+        }
+        skb->len  = len;
+        skb->tail = skb->data + len;
 }
 
 /**
@@ -993,6 +994,7 @@ static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
  *
  *      Cut the length of a buffer down by removing data from the tail. If
  *      the buffer is already under the length specified it is not modified.
+ *      The skb must be linear.
  */
 static inline void skb_trim(struct sk_buff *skb, unsigned int len)
 {
@@ -1003,12 +1005,10 @@ static inline void skb_trim(struct sk_buff *skb, unsigned int len)
 
 static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
 {
-        if (!skb->data_len) {
-                skb->len  = len;
-                skb->tail = skb->data+len;
-                return 0;
-        }
-        return ___pskb_trim(skb, len, 1);
+        if (skb->data_len)
+                return ___pskb_trim(skb, len);
+        __skb_trim(skb, len);
+        return 0;
 }
 
 static inline int pskb_trim(struct sk_buff *skb, unsigned int len)