Smack: prevent underflow in smk_set_cipso()

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.carpenter@oracle.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 2bae1fc..9c43080 100644 (file)
--- 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;