linux-kernel - Re: [PATCH v2 14/14] x86: Make software tag-based kasan available

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+fCnZdhvzUs6NWxCz+PcxBf=tz5xcsHOraKT5+y+vNJb2b-Lg@mail.gmail.com>
Date: Sat, 22 Feb 2025 16:06:34 +0100
From: Andrey Konovalov <andreyknvl@...il.com>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
Cc: kees@...nel.org, julian.stecklina@...erus-technology.de, 
	kevinloughlin@...gle.com, peterz@...radead.org, tglx@...utronix.de, 
	justinstitt@...gle.com, catalin.marinas@....com, wangkefeng.wang@...wei.com, 
	bhe@...hat.com, ryabinin.a.a@...il.com, kirill.shutemov@...ux.intel.com, 
	will@...nel.org, ardb@...nel.org, jason.andryuk@....com, 
	dave.hansen@...ux.intel.com, pasha.tatashin@...een.com, 
	ndesaulniers@...gle.com, guoweikang.kernel@...il.com, dwmw@...zon.co.uk, 
	mark.rutland@....com, broonie@...nel.org, apopple@...dia.com, bp@...en8.de, 
	rppt@...nel.org, kaleshsingh@...gle.com, richard.weiyang@...il.com, 
	luto@...nel.org, glider@...gle.com, pankaj.gupta@....com, 
	pawan.kumar.gupta@...ux.intel.com, kuan-ying.lee@...onical.com, 
	tony.luck@...el.com, tj@...nel.org, jgross@...e.com, dvyukov@...gle.com, 
	baohua@...nel.org, samuel.holland@...ive.com, dennis@...nel.org, 
	akpm@...ux-foundation.org, thomas.weissschuh@...utronix.de, surenb@...gle.com, 
	kbingham@...nel.org, ankita@...dia.com, nathan@...nel.org, ziy@...dia.com, 
	xin@...or.com, rafael.j.wysocki@...el.com, andriy.shevchenko@...ux.intel.com, 
	cl@...ux.com, jhubbard@...dia.com, hpa@...or.com, 
	scott@...amperecomputing.com, david@...hat.com, jan.kiszka@...mens.com, 
	vincenzo.frascino@....com, corbet@....net, maz@...nel.org, mingo@...hat.com, 
	arnd@...db.de, ytcoode@...il.com, xur@...gle.com, morbo@...gle.com, 
	thiago.bauermann@...aro.org, linux-doc@...r.kernel.org, 
	kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, linux-mm@...ck.org, 
	linux-arm-kernel@...ts.infradead.org, x86@...nel.org
Subject: Re: [PATCH v2 14/14] x86: Make software tag-based kasan available

On Fri, Feb 21, 2025 at 3:45 PM Maciej Wieczor-Retman
<maciej.wieczor-retman@...el.com> wrote:
>
> >What's the purpose of this config option? I think we can just change
> >the value of the KASAN_SHADOW_SCALE_SHIFT define when KASAN_SW_TAGS is
> >enabled.
>
> Well, I was aiming at later adding the "default 5 if KASAN_SW_TAGS_DENSE", and
> this way it would look much cleaner than the:
>
> if KASAN_SW_TAGS
>         if KASAN_SW_TAGS_DENSE
>                 KASAN_SHADOW_SCALE_SHIFT = 5
>         else
>                 KASAN_SHADOW_SCALE_SHIFT = 4
> else
>         KASAN_SHADOW_SCALE_SHIFT = 3

I think this is fine. It's still better than adding a non-configurable
config option.

> But now that I think of it, it should be possible to overwrite the
> KASAN_SHADOW_SCALE_SHIFT from non-arch code if dense mode is enabled.

This should also work. Especially since the dense mode will probably
work for arm64 as well.

But let's keep this series self-contained.

> That's a topic for the next series but I'd imagine all architectures would
> normally use the 16 memory bytes / shadow byte and if they'd care for the dense
> mode they'd go for 32 memory bytes / shadow byte. Or do you think that's a
> faulty assumption?

Probably, but for sure I don't know, not that many architectures that
care about memory tagging yet :)