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AJvYcCVLJK0OHiI2TBrsS2JvOrNBgGa8qwd5UqW1FtfQVJZGd5srF4H6txkQPZGJfbds78i4Zo6Wu4+p4A==@kvack.org X-Gm-Message-State: AOJu0YxI56JyK/7kh1WOodzVYECEus9MHSLxKjLViZ/g0T659fvOUWXD NmtljFNJOuTnRSrsj2dC/BvjGCQCgDAsVpbgQCmdTgQl04K0Jf74FztQ4YsYvuOkFH3bIEPnrrE YAGD6dozXTh30XYSIrJ3meKp2BWeMzbwyHGFhV93K X-Gm-Gg: ASbGncuF0iWvbFStrP+xtN71oan+4W+1a/8GUnHvQGMQIoEnutwa0h0tykaEp+se1el 7SATxI2VFW4NVSAYv4chcSoWBrs3+cLma0Q2L5535a/lATO82ymBOLU8XzoyxQnjd7k3ytgIh/d iLpGMJQWvNbGuzSn5K2kqvjr6P8zkTZgV5AMCGM8FfVIDoHg92jCd/ENvbTyOHJ2UgIhrTFSmKq Sbl3JzH3eXBMYY55G87EdpzgOqE+qUD8v0qUnkkCMDlQCDMio6Pvp3gtz1hBKimeF0fFfK9ECWf ihc= X-Google-Smtp-Source: AGHT+IHw6dFIKAHzPTv9mVtUGHjBlx7WlkdXf8MR1ZgGcxSTfN3zEfUpxsIIe3xlxd6CYLBEcLBlT5+Vp1Gkw1TXYKQ= X-Received: by 2002:a17:903:2343:b0:28e:7f50:5d80 with SMTP id d9443c01a7336-2902721336cmr7056975ad.7.1759861145158; Tue, 07 Oct 2025 11:19:05 -0700 (PDT) MIME-Version: 1.0 References: <20250315025852.it.568-kees@kernel.org> <20250315031550.473587-2-kees@kernel.org> <202510071001.11497F6708@keescook> In-Reply-To: From: Marco Elver Date: Tue, 7 Oct 2025 20:18:28 +0200 X-Gm-Features: AS18NWCHLWcuBl7emRjgyAd7xCJevIo8qneqm5GOzEKlmO2F3nZsj3gxx6OmYQU Message-ID: Subject: Re: [PATCH v4 2/2] slab: Introduce kmalloc_obj() and family To: "Christoph Lameter (Ampere)" Cc: Kees Cook , Matthew Wilcox , Vlastimil Babka , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Gustavo A . R . Silva" , Bill Wendling , Justin Stitt , Jann Horn , Przemek Kitszel , Linus Torvalds , Greg Kroah-Hartman , Sasha Levin , linux-mm@kvack.org, Miguel Ojeda , Nathan Chancellor , Peter Zijlstra , Nick Desaulniers , Jonathan Corbet , Jakub Kicinski , Yafang Shao , Tony Ambardar , Alexander Lobakin , Jan Hendrik Farr , Alexander Potapenko , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-doc@vger.kernel.org, llvm@lists.linux.dev, Matteo Rizzo Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Stat-Signature: dath1mesaak5rjp9bmkckgmx1fwbcx7d X-Rspamd-Queue-Id: 8EDFD1A0007 X-Rspamd-Server: rspam09 X-HE-Tag: 1759861146-666703 X-HE-Meta: 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 V60d+3Es 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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 Tue, 7 Oct 2025 at 19:47, Christoph Lameter (Ampere) wrote: > > On Tue, 7 Oct 2025, Kees Cook wrote: > > > But all of that is orthogonal to just _having_ the type info available. > > iOS did go the path of creating basically one slab cache for each > "type" of kmalloc for security reasons. > > See https://security.apple.com/blog/towards-the-next-generation-of-xnu-memory-safety/ We can get something similar to that with: https://lore.kernel.org/all/20250825154505.1558444-1-elver@google.com/ Pending compiler support which is going to become available in a few months (probably). That version used the existing RANDOM_KMALLOC_CACHES choice of 16 slab caches, but there's no fundamental limitation to go higher. Note, this mitigation is likely not as strong as we'd like to without SLAB_VIRTUAL (or so I'm told): https://lwn.net/Articles/944647/