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[221.241.217.81]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cad77651c2sm39542415ad.49.2026.07.05.17.19.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 05 Jul 2026 17:19:05 -0700 (PDT) Date: Mon, 06 Jul 2026 09:19:02 +0900 Message-ID: From: Hajime Tazaki To: akpm@linux-foundation.org Cc: liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, jannh@google.com, pfalcato@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: nommu: add sysctl_max_map_count() check for do_mmap() In-Reply-To: <20260705151512.5edabd9bb5d11cb6f1c6309f@linux-foundation.org> References: <20260702012830.667205-1-thehajime@gmail.com> <20260705151512.5edabd9bb5d11cb6f1c6309f@linux-foundation.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3F60414000A X-Stat-Signature: prc3k9sy885gmcdz8uzwfjgj4mikc9ce X-HE-Tag: 1783297147-421895 X-HE-Meta: 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 Am4w+rz5 pMgqvEj8TZwghwbcUbNKkx9QpG05V8+7LtrAuPH3VuEKBti2soKp8Dq2PPTirioskiWFCnD40wZkmMVjpwK2hdGFweTm57Ul3DI79H3RXpLL5OZZt9gHwm8rtv8WsRlvpUgvMJoc4P1VHFfCeq1BLwJ84WHGhGPVq1XcKxS/g3KykmIts+1n6cEGpymnxHrSlgPKijS0F3h/PKeCoD1Yhcp5UWmt8Zmy35kLcuUZ//++aaafLBxBsMYE5G7w1TKRFiHUOHSnqkZE1gXTfzrcgKruQbO0ZAYYopBoJHjehpF8CKE0JEQTyhCNcshF8GcR4pUm4vW+SDiPImzNs0QPCSSRqIrncHn+3Mk2TNpa3Uf2Sc6hzqQsTt6UDJex0kuvcchUY7Js1H7B/Y4GVSXB2Bb/92qI+CqjmD1tAKQpsUokIx8m9LXq2R3vFOoYltorGTRQtbab2g/ukFjRe1FyXgzrRBY1mx4cB4QSGpZO7IWuMxhI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 06 Jul 2026 07:15:12 +0900, Andrew Morton wrote: > > On Thu, 2 Jul 2026 10:28:30 +0900 Hajime Tazaki wrote: > > > The sysctl variable vm.max_map_count (sysctl_max_map_count) is not > > expose under !MMU case but used it wit the default vaule > > DEFAULT_MAX_MAP_COUNT as a limit of count. This is currently used when > > a vma entry is split into two chunks (split_vma()) but not used when > > allocated (do_mmap()). As a result, even if users request a large > > number of allocate memory, it will keep allocating until OOM happens. > > > > This commit introduces a check at the begining of do_mmap in nommu.c to > > prevent this situation. > > > > This is detected with a LTP (Linux Test Project) test, which linked > > below. > > AI review flagged a couple of issues in the current code, one quite > serious: > > https://sashiko.dev/#/patchset/20260702012830.667205-1-thehajime@gmail.com I will follow up with another patch for the issue detected here. btw, I found (and sashiko also detected) several typos for this particular patch. Can I send v2 patch with the additional fix, or do you prefer that I'll only send the additional patch ? anyway, thanks for your time to look at this. -- Hajime