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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> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260612044425.763060-1-dev.jain@arm.com> 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