Re: [PATCH for v6.3 regression] mm/mremap: fix vm_pgoff in vma_merge() case 3

[Jiri Slaby]

On 27. 04. 23, 16:27, Greg KH wrote:
> On Thu, Apr 27, 2023 at 04:09:59PM +0200, Vlastimil Babka wrote:
> > After upgrading build guests to v6.3, rpm started segfaulting for
> > specific packages, which was bisected to commit 0503ea8f5ba7 ("mm/mmap:
> > remove __vma_adjust()"). rpm is doing many mremap() operations with file
> > mappings of its db. The problem is that in vma_merge() case 3 (we merge
> > with the next vma, expanding it downwards) vm_pgoff is not adjusted as
> > it should when vm_start changes. As a result the rpm process most likely
> > sees data from the wrong offset of the file. Fix the vm_pgoff
> > calculation.
> >
> > For case 8 this is a non-functional change as the resulting vm_pgoff is
> > the same.
> >
> > Reported-and-bisected-by: Jiri Slaby <jirislaby@xxxxxxxxxx>
> > Reported-and-tested-by: Fabian Vogt <fvogt@xxxxxxxx>
> > Link: https://bugzilla.suse.com/show_bug.cgi?id=1210903
> > Fixes: 0503ea8f5ba7 ("mm/mmap: remove __vma_adjust()")
> > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > ---
> > Hi, I'm sending this patch on top of v6.3 as I think it should be
> > applied and backported to 6.3-stable rather sooner than later.
> > This means there would be a small conflict when merging mm/mm-stable
> > later. Alternatively it could be added to mm/mm-stable and upcoming 6.4
> > pull request, but then the stable backport would need adjustment.
> > It's up to Linus and Andrew.
>
> That's not how the stable tree works, sorry, it needs to be in Linus's
> tree _first_.

In upstream as:
commit 7e7757876f258d99266e7b3c559639289a2a45fe
Author: Vlastimil Babka <vbabka@xxxxxxx>
Date:   Thu Apr 27 16:09:59 2023 +0200

    mm/mremap: fix vm_pgoff in vma_merge() case 3

Please queue for 6.3.1.

thanks,
--
js
suse labs