Btrfs: deal with NULL acl sent to btrfs_set_acl

It is legal for btrfs_set_acl to be sent a NULL acl.  This
makes sure we don't dereference it.  A similar patch was sent by
Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 1898f8555f06..fa44e92e9b8f 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -112,12 +112,14 @@ static int btrfs_set_acl(struct btrfs_trans_handle *trans,
         switch (type) {
         case ACL_TYPE_ACCESS:
                 mode = inode->i_mode;
-                ret = posix_acl_equiv_mode(acl, &mode);
-                if (ret < 0)
-                        return ret;
-                ret = 0;
-                inode->i_mode = mode;
                 name = POSIX_ACL_XATTR_ACCESS;
+                if (acl) {
+                        ret = posix_acl_equiv_mode(acl, &mode);
+                        if (ret < 0)
+                                return ret;
+                        inode->i_mode = mode;
+                }
+                ret = 0;
                 break;
         case ACL_TYPE_DEFAULT:
                 if (!S_ISDIR(inode->i_mode))