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Commit 8b7b9324 authored by Pablo Neira's avatar Pablo Neira Committed by David S. Miller
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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: default avatarPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ff378ca1

lib/nlattr.c

+8 −2
Original line number 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 len = strlen(str) + 1;

	int d = nla_len(nla) - len;

	int len = strlen(str);

	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)

		d = memcmp(nla_data(nla), str, len);