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Subject: Re: [PATCH] mm/shrinker: avoid out-of-bounds read in
 set_shrinker_bit()
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From: Muchun Song <muchun.song@linux.dev>
In-Reply-To: <20260510183700.102475-1-devnexen@gmail.com>
Date: Mon, 11 May 2026 10:48:41 +0800
Cc: Andrew Morton <akpm@linux-foundation.org>,
 Dave Chinner <david@fromorbit.com>,
 Qi Zheng <qi.zheng@linux.dev>,
 Roman Gushchin <roman.gushchin@linux.dev>,
 linux-mm@kvack.org,
 linux-kernel@vger.kernel.org
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Message-Id: <3E00B1F3-9C41-4E41-892B-81BE19C3757C@linux.dev>
References: <20260510183700.102475-1-devnexen@gmail.com>
To: David Carlier <devnexen@gmail.com>
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> On May 11, 2026, at 02:37, David Carlier <devnexen@gmail.com> wrote:
>=20
> set_shrinker_bit() reads info->unit[shrinker_id_to_index(shrinker_id)]
> before checking shrinker_id against info->map_nr_max, so an id past =
the
> currently visible map_nr_max reads past the unit[] array before the
> WARN_ON_ONCE() catches it.
>=20
> Move the load into the bounded branch.
>=20
> Fixes: 307bececcd12 ("mm: shrinker: add a secondary array for =
shrinker_info::{map, nr_deferred}")
> Signed-off-by: David Carlier <devnexen@gmail.com>

Acked-by: Muchun Song <muchun.song@linux.dev>

Thanks.