linux-kernel - Re: [PATCH 4.4 133/146] ovl: Copy up underlying inodes ->i

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Date:	Wed, 3 Aug 2016 15:36:44 +0800
From:	Eryu Guan <eguan@...hat.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Vivek Goyal <vgoyal@...hat.com>,
	Miklos Szeredi <mszeredi@...hat.com>
Subject: Re: [PATCH 4.4 133/146] ovl: Copy up underlying inodes ->i_mode to
 overlay inode

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@...hat.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@...hat.com>
> Reported-by: Eryu Guan <eguan@...hat.com>
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.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@...uxfoundation.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 */
> 
>