ACK: [SRU][F][G][H][PATCH v2] UBUNTU: SAUCE: overlayfs: fix incorrect mnt_id of files opened from map_files

[Seth Forshee]

On Mon, May 03, 2021 at 08:37:18PM +0300, Alexander Mikhalitsyn wrote:
> On Fri, 30 Apr 2021 15:37:42 -0500
> Seth Forshee <seth.forshee at canonical.com> wrote:
> 
> > On Mon, Apr 26, 2021 at 11:11:21AM +0300, alexander at mihalicyn.com wrote:
> > > From: Alexander Mikhalitsyn <alexander at mihalicyn.com>
> > > 
> > > BugLink: https://bugs.launchpad.net/bugs/1857257
> > > 
> > > The hack was introduced in ("UBUNTU: SAUCE: overlayfs: allow with
> > > shiftfs as underlay") and it broke checkpoint/restore of docker
> > > contains:
> > > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1857257
> > > 
> > > The following script can be used to trigger the issue:
> > >   #!/bin/bash
> > > 
> > >   cat > test.py << EOF
> > >   import sys
> > > 
> > >   f = open("/proc/self/maps")
> > > 
> > >   for l in f.readlines():
> > >     if "python" not in l:
> > >       continue
> > >     print(l)
> > >     s = l.split()
> > >     start, end = s[0].split("-")
> > >     fname = s[-1]
> > >     print(start, end, fname)
> > >     break
> > >   else:
> > >     sys.exit(1)
> > > 
> > >   test_file1 = open(fname)
> > >   test_file2 = open("/proc/self/map_files/%s-%s" % (start, end))
> > > 
> > >   fdinfo1 = open("/proc/self/fdinfo/%d" % test_file1.fileno()).read()
> > >   fdinfo2 = open("/proc/self/fdinfo/%d" % test_file2.fileno()).read()
> > > 
> > >   if fdinfo1 != fdinfo2:
> > >     print("FAIL")
> > >     print(test_file1)
> > >     print(fdinfo1)
> > >     print(test_file2)
> > >     print(fdinfo2)
> > >     sys.exit(1)
> > >   print("PASS")
> > >   EOF
> > >   sudo docker run -it --privileged --rm -v `pwd`:/mnt python python /mnt/test.py
> > > 
> > > Thanks to Andrei Vagin for the reproducer and investigation of this problem.
> > > 
> > > Cc: Andrei Vagin <avagin at gmail.com>
> > > Cc: Adrian Reber <areber at redhat.com>
> > > Cc: Christian Brauner <christian.brauner at ubuntu.com>
> > > Cc: Stefan Bader <stefan.bader at canonical.com>
> > > Cc: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
> > > Cc: Krzysztof Kozlowski <krzysztof.kozlowski at canonical.com>
> > > 
> > > Fixes: d24b8a5 ("UBUNTU: SAUCE: overlayfs: allow with shiftfs as underlay")
> > > Signed-off-by: Alexander Mikhalitsyn <alexander at mihalicyn.com>
> > 
> > I tested with and without this patch using the xfstests overlay tests
> > and saw no regressions. The use of vm_prfile is limited to very few use
> > cases, all within proc, so I think this change should be safe.
> > 
> > Acked-by: Seth Forshee <seth.forshee at canonical.com>
> 
> Hi, Seth
> 
> Thanks for review and testing!
> Do I need to resend this patch with your "Acked-by" tag or I need to wait for another maintainer and get second ACK?

You don't need to resend at all, though the patch will need another ack.

Also, today I became aware of a stable patch for at least 5.11 which has
conflicts with this patch. I'm testing an updated version of the patch
with the conflicts resolved, which we might need to use for at least
hirsute/impish.

Seth