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b=RYGzJ9/p0iFShU47y10rrIgFqPZdTiGgb9DmbgiqklepkrzDPFw2kBC9/2zqeWEUW viaCxlogpvwX+3aCC0Sd8lUceLDljigJa9iLlCb9F10Yjlhj3iUQLny2d4YgsfoDa3 9/gwNyB3H1+V9zLO+cNJVvrzMZehr/KQStMXx3w7NBURr+o996im+MYc36G4g+NxEN se/C/q0CTuMLefGDtpMkVF12OHR0TuBO1Ct6i9ir8QX5vXEXIKFI4HlBRW8n78msRp hj62W4vFhO49wxFNmhDB+OVuLmD4BbTZ7PH5QxouxT1NQe2LKzMLX+QeyIgefcxJfB DoRApwQsIJc5A== Date: Thu, 5 Nov 2026 12:59:38 +0000 From: Harry Yoo To: "Vlastimil Babka (SUSE)" Cc: Andrey Ryabinin , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Geert Uytterhoeven , Conor Dooley , Damien Le Moal , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , kasan-dev@googlegroups.com Subject: Re: [PATCH v3 01/10] slab, kunit: pin test slabs by an extra allocation Message-ID: References: <20261105-slub_tiny_rework-v3-0-0484ce59eabb@kernel.org> <20261105-slub_tiny_rework-v3-1-0484ce59eabb@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105-slub_tiny_rework-v3-1-0484ce59eabb@kernel.org> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 413FE40005 X-Stat-Signature: bkzj55pa6h89bwmd79xqebj9f9q4nece X-Rspam-User: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793883581-354356 X-HE-Meta: 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 1XY3hpgf azAjXCRxMKvBYLc1QD1LY/LMrwoS0AAV990M3655Olf1zfuawcgQ+Tz9J7NHJMr+2xt7f84z/w+WOHrSZvCN5Aae6SMExh8VBjdviqcYqVe3iS+WJJ1d/JPlf1VbqIJ62f+fatH3HXnsKjJKlrwGp69LWDlMM73TpsE2VeA1H+LzMUGyEeL0Oxk1zV/GwaA9Hj98C2umKioR2fUzhPU7zNNdLmEk7ecirWEAkSnLleTmrNblexZhNtIg1nLZt9cHD2YJAIH9Lkm3ZUypR+btO3PL5ykZH1niGXLAafjq+IW0XSZ+uCh7LUiM0fz0sPY7DfTMIlSuDildNR+TZBdKwzulqdWaKhRV1qqhG+G2PjQU6u1vwZmBYFWlanUVSy2Gv3ioh/smYAFNP4vMPp0QZb5SIONipbj/Dr5rf Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 05, 2026 at 09:43:50AM +0100, Vlastimil Babka (SUSE) wrote: > Several of slab kunit tests allocate and free a single object from the > test cache, perform intentional UAF actions and validation, while > expecting the empty slab to stay on the partial list. > > This subtly relies on non-zero s->min_partial. It currently compile-time > defaults to a non-zero value, but in theory a sysfs write racing with > the kunit test could change it. > More importantly, the upcoming > CONFIG_SLUB_TINY changes will make it possible to run the kunit tests > with s->min_partial being a compile-time zero, which means the tests > will now do unintended UAF writes on the page allocator level, and also > report failures, as flagged by sashiko [1]. Makes sense. > To prevent this in a robust way, add an extra object allocation to the > tests, that will prevent the slab being freed. Use migrate_disable() to > prevent migration to a different NUMA node, which would place the > allocation to a different slab. > > [1] https://sashiko.dev/#/patchset/20261024-slub_tiny_rework-v2-0-bf1419ab5ffd@kernel.org?part=8 > > Signed-off-by: Vlastimil Babka (SUSE) > --- Looks good to me, Acked-by: Harry Yoo (Meta) -- Cheers, Harry / Hyeonggon