linux-kernel - [PATCH] smackfs: Prevent underflow in smk_set

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Message-ID: <5070f3eb-55e2-44db-a97d-41f9b9878c6d@moroto.mountain>
Date:   Thu, 6 Jul 2023 08:52:39 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] smackfs: Prevent underflow in smk_set_cipso()

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@...aro.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 5590eaad241b..25f67d1b5c73 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -896,7 +896,7 @@ 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 &&
-- 
2.39.2