| From | Ben Hutchings <> | Date | Mon, 28 Apr 2014 02:11:21 +0100 | Subject | [PATCH 3.2 12/94] netlink: don't compare the nul-termination in nla_strcmp |
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3.2.58-rc1 review patch. If anyone has any objections, please let me know.
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From: Pablo Neira <pablo@netfilter.org>
[ 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: Ben Hutchings <ben@decadent.org.uk> --- lib/nlattr.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/lib/nlattr.c +++ b/lib/nlattr.c @@ -299,9 +299,15 @@ int nla_memcmp(const struct nlattr *nla, */ 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);
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