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

[Greg Kroah-Hartman]

On Wed, Aug 03, 2016 at 04:04:55PM +0800, Eryu Guan wrote:
> On Wed, Aug 03, 2016 at 09:45:06AM +0200, Greg Kroah-Hartman wrote:
> > On Wed, Aug 03, 2016 at 03:36:44PM +0800, Eryu Guan wrote:
> > > 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@xxxxxxxxxx>
> > > > 
> > > > 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?
> > 
> > Does Linus's tree have the same problem?
> 
> Yes, 4.7 kernel hangs as well.
> 
> > 
> > > (The 4.6-stable tree faces the same question)
> > 
> > Are we just missing a patch to be applied here?
> 
> AFAICT, no patch is available to fix it yet. But I've reported the bug
> to Miklos (in RH bugzilla).

Ok, thanks, just mark whatever fix you all come up with, with a stable
marking, and I will pick up the fix when it gets merged to Linus's tree.

thanks,

greg k-h