Re: [PATCH 4.4 133/146] ovl: Copy up underlying inodes ->i_mode to overlay inode

Eryu Guan
2016-08-03T07:37:05Z

On Mon, Jul 25, 2016 at 01:56:28PM -0700, Greg Kroah-Hartman wrote:
> 4.4-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Vivek Goyal <vgoyal@redhat.com>
>
> commit 07a2daab49c549a37b5b744cbebb6e3f445f12bc upstream.
>
> Right now when a new overlay inode is created, we initialize overlay
> inode's ->i_mode from underlying inode ->i_mode but we retain only
> file type bits (S_IFMT) and discard permission bits.
>
> This patch changes it and retains permission bits too. This should allow
> overlay to do permission checks on overlay inode itself in task context.
>
> [SzM] It also fixes clearing suid/sgid bits on write.

This patch introduced a hang when writing to suid file, fstests
generic/355 could reproduce the hang easily, it only failed the test
without this patch and didn't hang the kernel.

Should we skip it for now and wait for a further fix?

(The 4.6-stable tree faces the same question)

Thanks,
Eryu

>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> Reported-by: Eryu Guan <eguan@redhat.com>
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> fs/overlayfs/inode.c | 3 +--
> fs/overlayfs/overlayfs.h | 1 +
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -412,12 +412,11 @@ struct inode *ovl_new_inode(struct super
> if (!inode)
> return NULL;
>
> - mode &= S_IFMT;
> -
> inode->i_ino = get_next_ino();
> inode->i_mode = mode;
> inode->i_flags |= S_NOATIME | S_NOCMTIME;
>
> + mode &= S_IFMT;
> switch (mode) {
> case S_IFDIR:
> inode->i_private = oe;
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -181,6 +181,7 @@ static inline void ovl_copyattr(struct i
> {
> to->i_uid = from->i_uid;
> to->i_gid = from->i_gid;
> + to->i_mode = from->i_mode;
> }
>
> /* dir.c */
>
>