[PATCH 4.9 135/212] Smack: fix another vsscanf out of bounds

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit a6bd4f6d9b07452b0b19842044a6c3ea384b0b88 ]

This is similar to commit 84e99e58e8d1 ("Smack: slab-out-of-bounds in
vsscanf") where we added a bounds check on "rule".

Reported-by: syzbot+a22c6092d003d6fe1122@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: f7112e6c9abf ("Smack: allow for significantly longer Smack labels v4")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 security/smack/smackfs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 2bfec47b8d5c5..2eba7c1e66630 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -928,6 +928,10 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
 
 	for (i = 0; i < catlen; i++) {
 		rule += SMK_DIGITLEN;
+		if (rule > data + count) {
+			rc = -EOVERFLOW;
+			goto out;
+		}
 		ret = sscanf(rule, "%u", &cat);
 		if (ret != 1 || cat > SMACK_CIPSO_MAXCATNUM)
 			goto out;
-- 
2.25.1