linux-kernel - [PATCH 5.7 144/163] Smack: slab-out-of-bounds in vsscanf

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Date:   Tue, 16 Jun 2020 17:35:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hillf Danton <hdanton@...a.com>,
        syzbot+bfdd4a2f07be52351350@...kaller.appspotmail.com,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: [PATCH 5.7 144/163] Smack: slab-out-of-bounds in vsscanf

From: Casey Schaufler <casey@...aufler-ca.com>

commit 84e99e58e8d1e26f04c097f4266e431a33987f36 upstream.

Add barrier to soob. Return -EOVERFLOW if the buffer
is exceeded.

Suggested-by: Hillf Danton <hdanton@...a.com>
Reported-by: syzbot+bfdd4a2f07be52351350@...kaller.appspotmail.com
Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/smack/smackfs.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -878,11 +878,21 @@ static ssize_t smk_set_cipso(struct file
 	else
 		rule += strlen(skp->smk_known) + 1;
 
+	if (rule > data + count) {
+		rc = -EOVERFLOW;
+		goto out;
+	}
+
 	ret = sscanf(rule, "%d", &maplevel);
 	if (ret != 1 || maplevel > SMACK_CIPSO_MAXLEVEL)
 		goto out;
 
 	rule += SMK_DIGITLEN;
+	if (rule > data + count) {
+		rc = -EOVERFLOW;
+		goto out;
+	}
+
 	ret = sscanf(rule, "%d", &catlen);
 	if (ret != 1 || catlen > SMACK_CIPSO_MAXCATNUM)
 		goto out;