Smack: fix another vsscanf out of bounds

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@syzkaller.appspotmail.com
Fixes: f7112e6c9abf ("Smack: allow for significantly longer Smack labels v4")
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 840a192..2bae1fc 100644 (file)
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -905,6 +905,10 @@ 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;