[PATCH 5.10 160/406] smackfs: Prevent underflow in smk_set_cipso()

Greg Kroah-Hartman
2023-09-17T19:27:22Z

From: Dan Carpenter <dan.carpenter@linaro.org>

[ Upstream commit 3ad49d37cf5759c3b8b68d02e3563f633d9c1aee ]

There is a upper bound to "catlen" but no lower bound to prevent
negatives. I don't see that this necessarily causes a problem but we
may as well be safe.

Fixes: e114e473771c ("Smack: Simplified Mandatory Access Control Kernel")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/smack/smackfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 3eabcc469669e..8403c91a6b297 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -895,7 +895,7 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
}

ret = sscanf(rule, "%d", &catlen);
- if (ret != 1 || catlen > SMACK_CIPSO_MAXCATNUM)
+ if (ret != 1 || catlen < 0 || catlen > SMACK_CIPSO_MAXCATNUM)
goto out;

if (format == SMK_FIXED24_FMT &&
--
2.40.1