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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> 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-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: 8i5hi65a3oktt9p8zt7ke6pewyxggyg4 X-Rspamd-Queue-Id: 3B19B180002 X-HE-Tag: 1781309816-871898 X-HE-Meta: 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 Rqq/p4I/ q+SQVi1qzd0ElulnY8oFbJGrujFxVGMS8Gt3VH6PB7UcvWFG8JkoNxeseTNFaSHB57jLyQf0ljtgJ3Xyc+UYgI0Y9mcnsKDIP4ea6Yi9hMmrW0Zd/ZRijBg5Ih1A8q/AF769dTgU9EdpJl+4p8rcLpabRAEv/84nLXLOFYTwNAk/rYMZobJh9VG1y5dYeOqlrWkVzjPofWy6nxLK6HB1k/eQbnUXCRVty9uonSo+2zqnFVcyGzpp2U/SGFdwGHqfL76X2hOZW6rup5n8B7cV9meqnom7sB4S2q9Q7nBBGep+/s2/BJdvIV90VFh3tcN5iLe7q9fmOhFkBW2iAXGp02wzfm33nWiiSXZllTLCNv6hyjxdtfwalobHef85OXrh9yYLaSdLZ5hPHfrns2nKXaBudekKSamG4KIDBKCmDQMVO5s/N5EHhW9Xm8+laCwBDU7Dm26435KXHjw2HQX2SFSrxesElK6GrqWGF5ziM1YyXLWRKc/wXN9n+vuSbQMc/pKSWqxnBee3DwsWBSUKT60RL9lAKeMlMQB6Y/cf1auQhmYOgxFTKJXwGVwIhbj5qa3oc Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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