Btrfs: should add a permission check for setfacl

On btrfs, do the following
------------------
# su user1
# cd btrfs-part/
# touch aaa
# getfacl aaa
  # file: aaa
  # owner: user1
  # group: user1
  user::rw-
  group::rw-
  other::r--
# su user2
# cd btrfs-part/
# setfacl -m u::rwx aaa
# getfacl aaa
  # file: aaa
  # owner: user1
  # group: user1
  user::rwx           <- successed to setfacl
  group::rw-
  other::r--
------------------
but we should prohibit it that user2 changing user1's acl.
In fact, on ext3 and other fs, a message occurs:
  setfacl: aaa: Operation not permitted

This patch fixed it.
Signed-off-by: Shi Weihua <shiwh@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 6ef7b26724e..6b4d0cca5c7 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -160,6 +160,9 @@ static int btrfs_xattr_acl_set(struct dentry *dentry, const char *name,
         int ret;
         struct posix_acl *acl = NULL;
 
+        if (!is_owner_or_cap(dentry->d_inode))
+                return -EPERM;
+
         if (value) {
                 acl = posix_acl_from_xattr(value, size);
                 if (acl == NULL) {