Re: [4.13-rc1 regression] copyup crashes kernel when initializing selinux

[Eryu Guan <eguan@redhat.com>]

On Mon, Jul 17, 2017 at 01:25:03PM +0200, Miklos Szeredi wrote:
> On Mon, Jul 17, 2017 at 05:37:41PM +0800, Eryu Guan wrote:
> > Hi all,
> > 
> > I hit a kernel crash with 4.13-rc1 kernel when running fstests
> > overlay/005. And git bisect pointed first bad to this commit
> > 
> > commit 09d8b586731bf589655c2ac971532c14cf272b63
> > Author: Miklos Szeredi <mszeredi@redhat.com>
> > Date:   Tue Jul 4 22:03:16 2017 +0200
> > 
> >     ovl: move __upperdentry to ovl_inode
> > 
> >     Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> > 
> > inode_doinit_with_dentry wants to read the upper inode's xattr to get
> > selinux information, and ovl_xattr_get() calls ovl_dentry_real(), which
> > depends on dentry->d_inode, but d_inode is null and not initialized yet
> > at this moment.
> > 
> > Mount overlay without selinux context mount option and trigger copyup
> > could reproduce the crash reliably. (The crash log I appended is from a
> > bisect run, so the kernel version is not exact 4.13-rc1.)
> 
> Could you please test following patch?

This patch works for me, but I just ran overlay/005, didn't run other
tests.

Thanks,
Eryu