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>
This commit is contained in:
Thomas Graf 2015-01-06 01:04:21 +01:00 committed by David S. Miller
parent a515abd777
commit 149118d893

View File

@ -520,8 +520,10 @@ static inline void *nlmsg_get_pos(struct sk_buff *skb)
*/
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);
}
}
/**