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

[liu weni <qingshenlwy@gmail.com>]

While the acl pointer is IS_ERR, We cannot get the correct return.

And the acl pointer is NULL. Oh, my god! The FOREACH_ACL_ENTRY will
call that.

---

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..4e0261b 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -213,6 +213,12 @@ posix_acl_permission(struct inode *inode, const
struct posix_acl *acl, int want)
 	const struct posix_acl_entry *pa, *pe, *mask_obj;
 	int found = 0;

+	if (!acl)
+		return -EINVAL;
+
+	if (IS_ERR(acl))
+		return PTR_ERR(acl);
+
 	FOREACH_ACL_ENTRY(pa, acl, pe) {
                 switch(pa->e_tag) {
                         case ACL_USER_OBJ: