vfs: ftruncate check IS_APPEND() on real upper inode

ftruncate an overlayfs inode was checking IS_APPEND() on
overlay inode, but overlay inode does not have the S_APPEND flag.

Check IS_APPEND() on real upper inode instead.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/open.c b/fs/open.c
index 949cef29c3bb..993a91d20cc7 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -193,7 +193,8 @@ static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
                 goto out_putf;
 
         error = -EPERM;
-        if (IS_APPEND(inode))
+        /* Check IS_APPEND on real upper inode */
+        if (IS_APPEND(file_inode(f.file)))
                 goto out_putf;
 
         sb_start_write(inode->i_sb);