Re: [RFC PATCH] mm/damon/core: handle region split failure in apply_min_nr_regions()

[SJ Park <sj@kernel.org>]

On Fri, 17 Jul 2026 18:03:12 -0700 SJ Park <sj@kernel.org> wrote:

> On Fri, 17 Jul 2026 17:43:00 -0700 SJ Park <sj@kernel.org> wrote:
> 
> > damon_apply_min_nr_regions() repeatedly split each region until its size
> > becomes small enough to meet the user-defined low limit of the number of
> > regions.  The loop assumes the split operation (damon_split_region_at())
> > will always succeed and create the new region.  But the operation could
> > silently fail for memory allocation failures, for example.  If such
> > failure happens and the region was the last region, the linked
> > list-based next region fetching returns invalid pointer.  As a result,
> > invalid memory dereference and corruption could happen.  Fix by breaking
> > the loop in the corner case.
> 
> Sashiko found no blocker for this series.  Sashiko sent findings to damon@
> mailing list [1], and I replied to all the comments.  Please read those for
> details.

My intention was to add this reply to other mail[1] but I only mistakenly
replied here.

This is true, though.  Sashiko found no issue in this patch.  But that means
nothing since this is an RFC.  I will repost this patch after dropping the RFC
and rebasing to latest mm-new, tomorrow.

[1] https://lore.kernel.org/20260718011322.94001-1-sj@kernel.org

> 
> [1] https://lore.kernel.org/damon/


Thanks,
SJ

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