netlink: Warn on unordered or illegal nla_nest_cancel() or nlmsg_cancel()
Calling nla_nest_cancel() in a different order as the nesting was
built up can lead to negative offsets being calculated which
results in skb_trim() being called with an underflowed unsigned
int. Warn if mark < skb->data as it's definitely a bug.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 6415835..d5869b9 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -520,8 +520,10 @@
*/
static inline void nlmsg_trim(struct sk_buff *skb, const void *mark)
{
- if (mark)
+ if (mark) {
+ WARN_ON((unsigned char *) mark < skb->data);
skb_trim(skb, (unsigned char *) mark - skb->data);
+ }
}
/**