Re: [PATCH 6.18.y] mm/mseal: update VMA end correctly on merge

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Mar 30, 2026 at 12:00:21PM +0100, Lorenzo Stoakes (Oracle) wrote:
> Previously we stored the end of the current VMA in curr_end, and then upon
> iterating to the next VMA updated curr_start to curr_end to advance to the
> next VMA.
> 
> However, this doesn't take into account the fact that a VMA might be
> updated due to a merge by vma_modify_flags(), which can result in curr_end
> being stale and thus, upon setting curr_start to curr_end, ending up with
> an incorrect curr_start on the next iteration.
> 
> Resolve the issue by setting curr_end to vma->vm_end unconditionally to
> ensure this value remains updated should this occur.
> 
> While we're here, eliminate this entire class of bug by simply setting
> const curr_[start/end] to be clamped to the input range and VMAs, which
> also happens to simplify the logic.
> 
> Reported-by: Antonius <antonius@bluedragonsec.com>
> Closes: https://lore.kernel.org/linux-mm/CAK8a0jwWGj9-SgFk0yKFh7i8jMkwKm5b0ao9=kmXWjO54veX2g@mail.gmail.com/
> Suggested-by: David Hildenbrand (ARM) <david@kernel.org>
> Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> Reviewed-by: Pedro Falcato <pfalcato@suse.de>
> Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
> Fixes: 6c2da14ae1e0 ("mm/mseal: rework mseal apply logic")
> Cc: <stable@vger.kernel.org>
> (cherry picked from commit 88995f43fdc2045ff0b030ca054898483004de36)

Not a valid git id :(