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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Uladzislau Rezki , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrey Konovalov , Marco Elver , Vincenzo Frascino , Peter Collingbourne , Will Deacon , Ryan.Roberts@arm.com, david.hildenbrand@arm.com Subject: Re: [PATCH v2 2/3] kasan: skip HW tagging for all kernel thread stacks Message-ID: References: <20260324132631.482520-1-usama.anjum@arm.com> <20260324132631.482520-3-usama.anjum@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: rw3huikpujze5zati5wxs6kh5mgomkrm X-Rspamd-Queue-Id: 08F9E180005 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1775846225-317317 X-HE-Meta: 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 7hMRkz7b MWktqQ1v1Oq1YCLuxH6i5UnpI1b97VF3XTKjvxjG4H/b/EOBt/Z55PxdqOJlOkrVY95l55iORKoW1qseyjbdjmuVqIaAlG5rpvah/zhtt0IbOW5udliBr9u/NudixamkRY4Xlf1wdtIGMkPKJw6Vvq+uOZxfbS++gWnbtEHb2w7Wzjk9MRW4aGx6KvP/ip01uy4hMB6xy1FNnLQhC5vpVtKKmWzURnAlpau07tEwbfYeIvVHIr1MHEAIGGG3ztXoTLLu0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 10, 2026 at 07:32:23PM +0100, Catalin Marinas wrote: > What the original approach might help with is use-after-realloc in case > we had a tagged pointer in a past life of a page and it still works now. > Oh well, that's I guess for other types of hardening to address like > delayed reallocation. Another thought (for a separate series) - we could try to map the stack as Untagged (unless stack tagging is enabled; needs compiler instrumentation) and enable canonical tag checking (newer addition to MTE). This way, any stray tagged pointer won't work on the stack since it needs a 0xf tag (canonical). -- Catalin