[PATCH 5.8 303/464] Smack: prevent underflow in smk_set_cipso()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpen...@oracle.com>

[ Upstream commit 42a2df3e829f3c5562090391b33714b2e2e5ad4a ]

We have an upper bound on "maplevel" but forgot to check for negative
values.

Fixes: e114e473771c ("Smack: Simplified Mandatory Access Control Kernel")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
Signed-off-by: Casey Schaufler <ca...@schaufler-ca.com>
Signed-off-by: Sasha Levin <sas...@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 2bae1fc493d16..9c4308077574c 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -884,7 +884,7 @@ static ssize_t smk_set_cipso(struct file *file, const char 
__user *buf,
        }
 
        ret = sscanf(rule, "%d", &maplevel);
-       if (ret != 1 || maplevel > SMACK_CIPSO_MAXLEVEL)
+       if (ret != 1 || maplevel < 0 || maplevel > SMACK_CIPSO_MAXLEVEL)
                goto out;
 
        rule += SMK_DIGITLEN;
-- 
2.25.1