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Fri, 21 Nov 2025 15:20:47 -0800 (PST) From: Joshua Hahn To: Vlastimil Babka Cc: David Hildenbrand , "Liam R. Howlett" , Andrew Morton , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, Kees Cook Subject: Re: [PATCH] mm/mm_init: Pull CONFIG_DEBUG_CHECK_PAGES out of CONFIG_DEBUG_VM Date: Fri, 21 Nov 2025 15:20:43 -0800 Message-ID: <20251121232044.3120695-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: kjmtixjyghsue7fawayis8xnnr66cbcc X-Rspam-User: X-Rspamd-Queue-Id: DA7DC1A0005 X-Rspamd-Server: rspam10 X-HE-Tag: 1763767248-991526 X-HE-Meta: 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 GzX4Cgak 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 21 Nov 2025 23:03:01 +0100 Vlastimil Babka wrote: > On 11/21/25 21:44, Joshua Hahn wrote: > > Use-after-free and double-free bugs can be very difficult to track down. > > The kernel is good at tracking these and preventing bad pages from being > > used/created through simple checks gated behind "check_pages_enabled". > > > > Currently, the only ways to enable this flag is by building with > > CONFIG_DEBUG_VM, or as a side effect of other checks such as > > init_on_{alloc, free}, page_poisoning, or debug_pagealloc among others. > > These solutions are powerful, but may often be too coarse in balancing > > the performance vs. safety that a user may want, particularly in > > latency-sensitie production environments. > > OK. Would a boot parameter work for you instead? It's more flexible than a > config option. Then we could perhaps also decouple it from > init_on_alloc/init_on_free as it's a bit odd side-effect for those anyway. Hi Vlastimil, thanks for the quick review! Yes, I think a boot parameter would also work perfectly fine. There's nothing in particular about making it a build config that I think is necessary here. So happy to make it a boot parameter, and also decouple it like you suggested! I'll spin up something and submit a v2. Thanks again for your review! Joshua