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Sun, 25 Oct 2026 12:01:18 -0700 (PDT) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e3ebc3bcdsm10026651f8f.13.2026.10.25.12.01.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 25 Oct 2026 12:01:17 -0700 (PDT) Message-ID: <533c4ef7-e008-4439-be40-1aa2a074dfd8@gmail.com> Date: Sun, 25 Oct 2026 20:01:16 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fs/proc/task_mmu: fix missed VMAs when reading /proc/PID/maps and friends To: "David Hildenbrand (Arm)" , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Suren Baghdasaryan , Shakeel Butt Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org References: <20261025-per_vma_maps-v1-1-c4eec45b9387@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261025-per_vma_maps-v1-1-c4eec45b9387@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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 Tested-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a