From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8E2BE280A5A; Thu, 18 Jun 2026 13:35:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781789732; cv=none; b=ooyl01CjMJ/GuSbBaHKJ9gF4hYgUGHuSpKdcfdjhqkTJGRiLQKWGFrjsdWPMFLGf8+VwUkgBT44ASy1d5bOOVQQttF0WGeUU6E8NAZPxXXuDRe8NtUEuKQTND6O0NcyzGuyZkqPDeOnWw+oSjYd+NJh/mi/dRTSefh3/i9RKpNM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781789732; c=relaxed/simple; bh=9RXFf2anX6QtDPr4e4nEY2mr6aMgIgsi2g2c8QfoVYo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=e+350ra56ZQkLVkqd7Wz9Oa/bEmEB7CWRc3gm6omc5pn3bWpLYnPhKbSMwkFGZVBH8VahbPpJAV4/KCBCnUr4y1FpmJX96F8u03uSrV5pSDe1MjhyF7TlLrZfRPSjFBdIFaiH8HTZQtYndnCVg8+phcfINj7U1D6ITHSKbg7krY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BLS8wM+7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BLS8wM+7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F1D81F000E9; Thu, 18 Jun 2026 13:35:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781789731; bh=Rk6LmjIbCHsYPNdyORQTlWLED3QFUIZxJF66Poqak0U=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BLS8wM+7lNGipicaKQI08fr6BvpoZb8eQFBGEtcAz6VB81AbZ8KRuoXZm/Aq6wj6g xYRyXinasz+XrelPwmme8HY0hJ0ltYqS7UnTdHA7izE6XGuxihVc1nWVx+fKC1kmql GXJK3FKZnkS6zs2PST4qZc8YbPG8DmkHqC3xOi6R3Wz3pH9kxCBrsegUncuDz7o5ck StCGUVzgPGABGUhAiUQlubgvBqSbcV7T1IBtE9Mb+0+1jKP2o33viI4bIXnP2NWDEX qOD5DMWfmOGGGmSnmwPlRl8aptuhu4ojY5/eMHNHNAs7LYYDoADnvEBTngkwFmCdZ3 Qx/OQO3CyEb6Q== Message-ID: Date: Thu, 18 Jun 2026 22:35:15 +0900 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/2] kasan: hw_tags: Add option to tag only at allocation time To: Dev Jain , ryabinin.a.a@gmail.com, akpm@linux-foundation.org, corbet@lwn.net Cc: 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 References: <20260612044425.763060-1-dev.jain@arm.com> Content-Language: en-US From: Harry Yoo In-Reply-To: <20260612044425.763060-1-dev.jain@arm.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------RrLQl9DO89jp5rWKR4YTMpyy" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------RrLQl9DO89jp5rWKR4YTMpyy Content-Type: multipart/mixed; boundary="------------y0w8N2KinVP4PMHfeQRfXe6b"; protected-headers="v1" From: Harry Yoo To: Dev Jain , ryabinin.a.a@gmail.com, akpm@linux-foundation.org, corbet@lwn.net Cc: 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 Message-ID: Subject: Re: [RFC PATCH 0/2] kasan: hw_tags: Add option to tag only at allocation time References: <20260612044425.763060-1-dev.jain@arm.com> In-Reply-To: <20260612044425.763060-1-dev.jain@arm.com> --------------y0w8N2KinVP4PMHfeQRfXe6b Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi Dev, On 6/12/26 1:44 PM, 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. I think most of overhead when enabling MTE comes from loading and validing tags for every memory access (either in SYNC or ASYNC mode), rather than from storing tags. > 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. >=20 > Hence, not catching "use-after-free-before-reallocation" and not catchi= ng > "double-free" will be the compromise for reduced KASAN overhead. I doubt users who care about security enough to enable HW_TAGS KASAN are willing to compromise on security just to save a few instructions to store tags in the free path. To me, it looks like too much of a compromise on security for little performance gain. > This is an RFC because we are not clear about the performance benefit. > > Android folks, please help with testing! >=20 > --- > Applies on Linus master (9716c086c8e8). >=20 > Dev Jain (2): > kasan: hw_tags: Use KASAN_PAGE_REDZONE for vmalloc redzoning > kasan: hw_tags: Add boot option to elide free time poisoning >=20 > Documentation/dev-tools/kasan.rst | 4 +++ > mm/kasan/hw_tags.c | 45 +++++++++++++++++++++++++++++--= > mm/kasan/kasan.h | 23 +++++++++++++++- > 3 files changed, 69 insertions(+), 3 deletions(-) >=20 --=20 Cheers, Harry / Hyeonggon --------------y0w8N2KinVP4PMHfeQRfXe6b-- --------------RrLQl9DO89jp5rWKR4YTMpyy Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature.asc" -----BEGIN PGP SIGNATURE----- iHUEARYKAB0WIQQQ1ub6gR5ogjaKRmOGXBN6rc5S1gUCajP0EwAKCRCGXBN6rc5S 1jNWAQDzVUDBUPeyt5upXL1mOoO9vGDvDLtilfxpmlxg7GO2qAD/YQLyoBRsQlGb zVC6FeFHHk+biv6lxpZCj6qBEzmyqwY= =XQEH -----END PGP SIGNATURE----- --------------RrLQl9DO89jp5rWKR4YTMpyy--