[PATCHv4 1/3]posix_acl: Add the acl pointer check

[liu weni <qingshenlwy@gmail.com>]

If the acl pointer is NULL or have some error, the acl is invalid.
The Macro of FOREACH_ACL_ENTRY will make some error.

---
Signed-off-by: Liuwenyi <qingshenlwy@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

---
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 39df95a..d4bacb9 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -76,6 +76,12 @@ posix_acl_valid(const struct posix_acl *acl)
 	unsigned int id = 0;  /* keep gcc happy */
 	int needs_mask = 0;

+	if (!acl)
+		return -EINVAL;
+
+	if (IS_ERR(acl))
+		return PTR_ERR(acl);
+
 	FOREACH_ACL_ENTRY(pa, acl, pe) {
 		if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 			return -EINVAL;