cifs: check whether acl is valid early

Dan reported that acl is dereferenced before being checked and this is a
valid problem. Fix it be erroring out early instead of doing it later after
we've already relied on acl to be a valid pointer.

Fixes: dc1af4c4b472 ("cifs: implement set acl method")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index 6a9f03c..c647f0d 100644 (file)
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -1764,6 +1764,10 @@ int cifs_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
                rc = PTR_ERR(full_path);
                goto out;
        }
+
+       if (!acl)
+               goto out;
+
        /* return dos attributes as pseudo xattr */
        /* return alt name if available as pseudo attr */
 
@@ -1778,8 +1782,6 @@ int cifs_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 
        switch (type) {
        case ACL_TYPE_ACCESS:
-               if (!acl)
-                       goto out;
                if (sb->s_flags & SB_POSIXACL)
                        rc = cifs_do_set_acl(xid, pTcon, full_path, acl,
                                             ACL_TYPE_ACCESS,
@@ -1788,8 +1790,6 @@ int cifs_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
                break;
 
        case ACL_TYPE_DEFAULT:
-               if (!acl)
-                       goto out;
                if (sb->s_flags & SB_POSIXACL)
                        rc = cifs_do_set_acl(xid, pTcon, full_path, acl,
                                             ACL_TYPE_DEFAULT,