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

[Greg KH]

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_.

thanks,

greg k-h