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Subject[PATCH 3.12 64/72] netlink: don't compare the nul-termination in nla_strcmp
Date
From: Pablo Neira <pablo@netfilter.org>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

[ Upstream commit 8b7b932434f5eee495b91a2804f5b64ebb2bc835 ]

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
lib/nlattr.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/nlattr.c b/lib/nlattr.c
index 18eca7809b08..fc6754720ced 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -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);

--
1.9.2


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