From: "Jose A. Perez de Azpillaga" <azpijr@gmail.com>
To: "David Hildenbrand (Arm)" <david@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Liam R. Howlett" <liam@infradead.org>,
Lorenzo Stoakes <ljs@kernel.org>,
Vlastimil Babka <vbabka@kernel.org>, Jann Horn <jannh@google.com>,
Pedro Falcato <pfalcato@suse.de>,
Suren Baghdasaryan <surenb@google.com>,
Shakeel Butt <shakeel.butt@linux.dev>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org
Subject: Re: [PATCH] fs/proc/task_mmu: fix missed VMAs when reading /proc/PID/maps and friends
Date: Sun, 25 Oct 2026 20:01:16 +0100 [thread overview]
Message-ID: <533c4ef7-e008-4439-be40-1aa2a074dfd8@gmail.com> (raw)
In-Reply-To: <20261025-per_vma_maps-v1-1-c4eec45b9387@kernel.org>
On 10/25/26 11:43 AM, David Hildenbrand (Arm) wrote:
[snip]
> Fixes: 5631da56c9a8 ("fs/proc/task_mmu: read proc/pid/maps under per-vma lock")
> Fixes: ea3085dd7a4e ("fs/proc/task_mmu: read proc/pid/{smaps|numa_maps} under per-vma lock")
> Fixes: 0e985559d72a ("proc/task_mmu: read proc/pid/smaps_rollup under per-vma lock")
PROCMAP_QUERY does the same fresh lookup, shouldn't d9d1c2d81797
("fs/proc/task_mmu: execute PROCMAP_QUERY ioctl under per-vma locks") be
here as well? (commit tracked down by an LLM)
[snip]
> There is the issue with seqcount overflows that Lorenzo is tackling. It
> probably interacts here as well? Likely, but that's an independent issue
> to resolve.
the saved seq is reset on every m_start() and query, so a wrap would
need 2^31 write locks inside one read() or ioctl, I don't think it
matters in practice :)
I tested it on x86_64 in qemu with KASAN, lockdep and DEBUG_VM on top of
mm-unstable, the maps holes I hit there are gone. Also, the code LGTM:
Reviewed-by: Jose A. Perez de Azpillaga <azpijr@gmail.com>
Tested-by: Jose A. Perez de Azpillaga <azpijr@gmail.com>
--
cheers,
jose a. p-a
next prev parent reply other threads:[~2026-10-25 19:01 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-25 10:43 [PATCH] fs/proc/task_mmu: fix missed VMAs when reading /proc/PID/maps and friends David Hildenbrand (Arm)
2026-10-25 14:55 ` Suren Baghdasaryan
2026-10-25 19:01 ` Jose A. Perez de Azpillaga [this message]
2026-10-26 10:04 ` David Hildenbrand (Arm)
2026-10-26 15:56 ` Andrew Morton
2026-10-26 13:35 ` Lorenzo Stoakes (ARM)
2026-10-26 13:38 ` Lorenzo Stoakes (ARM)
2026-10-26 16:16 ` Suren Baghdasaryan
2026-10-26 17:19 ` David Hildenbrand (Arm)
2026-10-26 17:26 ` Lorenzo Stoakes (ARM)
2026-10-26 18:01 ` Liam R. Howlett
2026-10-26 18:05 ` Lorenzo Stoakes (ARM)
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