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Fri, 12 Jun 2026 17:16:53 -0700 (PDT) Received: from google.com ([2a00:79e0:2e51:8:e362:1a25:b90f:e3ee]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3081ea43b80sm5190375eec.21.2026.06.12.17.16.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jun 2026 17:16:53 -0700 (PDT) Date: Fri, 12 Jun 2026 17:16:47 -0700 From: Isaac Manjarres To: Dev Jain Cc: ryabinin.a.a@gmail.com, akpm@linux-foundation.org, corbet@lwn.net, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, workflows@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, kaleshsingh@google.com, 21cnbao@gmail.com, david@kernel.org, will@kernel.org, catalin.marinas@arm.com Subject: Re: [RFC PATCH 0/2] kasan: hw_tags: Add option to tag only at allocation time Message-ID: References: <20260612044425.763060-1-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260612044425.763060-1-dev.jain@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260612_171656_888145_1E71E69D X-CRM114-Status: GOOD ( 19.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jun 12, 2026 at 04:44:22AM +0000, Dev Jain wrote: > Introduce a boot option to tag only at allocation time of the objects. This > reduces KASAN MTE overhead, the tradeoff being reduced ability of > catching bugs. > > Now, when a memory object will be freed, it will retain the random tag it > had at allocation time. This compromises on catching UAF bugs, till the > time the object is not reallocated, at which point it will have a new > random tag. > > Hence, not catching "use-after-free-before-reallocation" and not catching > "double-free" will be the compromise for reduced KASAN overhead. > > This is an RFC because we are not clear about the performance benefit. > > Android folks, please help with testing! > > --- > Applies on Linus master (9716c086c8e8). > > Dev Jain (2): > kasan: hw_tags: Use KASAN_PAGE_REDZONE for vmalloc redzoning > kasan: hw_tags: Add boot option to elide free time poisoning > > Documentation/dev-tools/kasan.rst | 4 +++ > mm/kasan/hw_tags.c | 45 +++++++++++++++++++++++++++++-- > mm/kasan/kasan.h | 23 +++++++++++++++- > 3 files changed, 69 insertions(+), 3 deletions(-) > > -- > 2.43.0 I tested out this series on one of our devices that has MTE support, and didn't see any functional issues. One thing I did notice though, and it's independent of this patch, is that the vmalloc_oob is failing, but that happens even if these patches aren't present. Thanks, Isaac