Merge tag 'Smack-for-5.9' of git://github.com/cschaufler/smack-next

Pull smack updates from Casey Schaufler:
 "Minor fixes to Smack for the v5.9 release.

  All were found by automated checkers and have straightforward
  resolution"

* tag 'Smack-for-5.9' of git://github.com/cschaufler/smack-next:
  Smack: prevent underflow in smk_set_cipso()
  Smack: fix another vsscanf out of bounds
  Smack: fix use-after-free in smk_write_relabel_self()

Author: torvalds

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;
@@ -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;
@@ -2720,7 +2724,6 @@ static int smk_open_relabel_self(struct inode *inode, struct file *file)
 static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
-	struct task_smack *tsp = smack_cred(current_cred());
 	char *data;
 	int rc;
 	LIST_HEAD(list_tmp);
@@ -2745,11 +2748,21 @@ static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf,
 	kfree(data);
 
 	if (!rc || (rc == -EINVAL && list_empty(&list_tmp))) {
+		struct cred *new;
+		struct task_smack *tsp;
+
+		new = prepare_creds();
+		if (!new) {
+			rc = -ENOMEM;
+			goto out;
+		}
+		tsp = smack_cred(new);
 		smk_destroy_label_list(&tsp->smk_relabel);
 		list_splice(&list_tmp, &tsp->smk_relabel);
+		commit_creds(new);
 		return count;
 	}
-
+out:
 	smk_destroy_label_list(&list_tmp);
 	return rc;
 }