Commit 8b7b9324 authored Apr 01, 2014 by Pablo Neira Committed by David S. Miller Apr 01, 2014

netlink: don't compare the nul-termination in nla_strcmp



nla_strcmp compares the string length plus one, so it's implicitly
including the nul-termination in the comparison.

 int nla_strcmp(const struct nlattr *nla, const char *str)
 {
        int len = strlen(str) + 1;
        ...
                d = memcmp(nla_data(nla), str, len);

However, if NLA_STRING is used, userspace can send us a string without
the nul-termination. This is a problem since the string
comparison will not match as the last byte may be not the
nul-termination.

Fix this by skipping the comparison of the nul-termination if the
attribute data is nul-terminated. Suggested by Thomas Graf.

Cc: Florian Westphal <fw@strlen.de>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent ff378ca1

lib/nlattr.c

+8 −2

Original line number	Original line	Diff line number	Diff line
	@@ -303,9 +303,15 @@ int nla_memcmp(const struct nlattr nla, const void data,
	*/		*/
	int nla_strcmp(const struct nlattr nla, const char str)		int nla_strcmp(const struct nlattr nla, const char str)
	{		{
	int len = strlen(str) + 1;		int len = strlen(str);
	int d = nla_len(nla) - len;		char *buf = nla_data(nla);
			int attrlen = nla_len(nla);
			int d;

			if (attrlen > 0 && buf[attrlen - 1] == '\0')
			attrlen--;

			d = attrlen - len;
	if (d == 0)		if (d == 0)
	d = memcmp(nla_data(nla), str, len);		d = memcmp(nla_data(nla), str, len);

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