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b=GNNoPCnYfdqBton8YNLsVJxe0Vx6acTMuSP3LmHDTWzmprfUEf4d8l39/ANjOMBmI 6Xxd+ytmKvCuQPLFKt8s3JEkL9fDULs+kWLp52HgqZI5BCimG2ca+whU7pLZdjlG17 IwA91N00zqgrhCajC4A9PHIrzNd/dV0kfrF7mQRUt/+VO6HRQZ67D69Ls0eFaOnBX2 0pLzQa9J6WnCoPKUgpU0cKWtP+EWSKqovVNIOTwHwtEDcdhDsUbxIp37cxpE+4zEuO Q1NFP57GQdDnRiJGbUVatKjNeGrNzR+4eg8PaVb3f6g+BIXpjKj/ipCQbx9XycRQc+ MR00djAuV0QNg== Date: Sun, 30 Aug 2026 15:11:23 +0000 From: Harry Yoo To: Longlong Xia Cc: vbabka@kernel.org, akpm@linux-foundation.org, hao.li@linux.dev, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Longlong Xia Subject: Re: [PATCH v2 1/1] mm/slab_common: reject zero object_size before calculate_alignment Message-ID: References: <20260826015506.3178758-1-xialonglong2025@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260826015506.3178758-1-xialonglong2025@163.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4B48014000B X-Stat-Signature: zsqwp8oiaj1so4w4ygpf46g8hizz7hjq X-HE-Tag: 1788102689-435251 X-HE-Meta: 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 pRb2fIvm ynJ6TpzMeSiou79T95fHvnywDL/FoQB8/XOgOL8Nst2/emCMt21VPKwIlv2CJVh4BfK3QPDj5IP/pYDDBTmF+R3pd77e6SksAI0FUIU/Nhyv+55nBpuNhixM7X9tj9svkHhEY/aKjS6Yq4VyN/aOM/R9j4CBKVOJcJ9/48KL36GoKnUD7ccuicpymsU96fGQIIm15Qmf25oAoML0OYJOfucxDWhm/gHFL6MONgz/+A45I9rRiH1x81Ny7M7RPMoIgoxdRPWW9C9vIAn8Ksfb6gn8YyaDJ5ouFHYIJ1i0V+jVuawKFH85+ZY3Lvya/ViCaDjnGyplyUkOYihdPmRxlRzDHDw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 26, 2026 at 09:55:06AM +0800, Longlong Xia wrote: > From: Longlong Xia > > calculate_alignment() with SLAB_HWCACHE_ALIGN halves ralign in a > while (size <= ralign / 2) loop. When size is 0, ralign eventually > reaches 0 and the condition stays true indefinitely, hanging the > kernel. > > kmem_cache_sanity_check() rejected size > KMALLOC_MAX_SIZE but not > size == 0. Add !size to the check so a 0-size kmem_cache_create() is > caught on CONFIG_DEBUG_VM builds, where it can be diagnosed when it > surfaces. > > Suggested-by: Hao Li > Assisted-by: Codex:gpt-5.6-sol > Signed-off-by: Longlong Xia > --- > Changes in v2: > - Drop the !object_size check in __kmem_cache_create_args() that v1 > added to the always-compiled path, and keep the guard only in the > debug-only kmem_cache_sanity_check(), as suggested by Hao Li. > > Link: https://lore.kernel.org/all/20260824092454.1693745-1-xialonglong2025@163.com/ > --- The patch is small and benign enough, so: Reviewed-by: Harry Yoo (Meta) However, to be honest I don't understand why anyone would ever try to create a kmem_cache with size == 0. It doesn't make any sense. I'd strongly encourage not addressing every theoretical issue raised by an LLM that doesn't bother you or somebody else. -- Cheers, Harry / Hyeonggon