linux-kernel - Re: [PATCH 00/15] kasan: x86: arm64: risc-v: KASAN tag-based mode for x86

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Message-ID: <239de2b9-0787-4105-a481-418dbd4d861e@intel.com>
Date: Thu, 6 Feb 2025 13:41:29 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Christoph Lameter (Ampere)" <cl@...two.org>,
 Jessica Clarke <jrtc27@...c27.com>
Cc: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, luto@...nel.org,
 xin@...or.com, kirill.shutemov@...ux.intel.com, palmer@...belt.com,
 tj@...nel.org, andreyknvl@...il.com, brgerst@...il.com, ardb@...nel.org,
 dave.hansen@...ux.intel.com, jgross@...e.com, will@...nel.org,
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 julian.stecklina@...erus-technology.de, peterz@...radead.org,
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 linux-doc@...r.kernel.org, "Shutemov, Kirill" <kirill.shutemov@...el.com>
Subject: Re: [PATCH 00/15] kasan: x86: arm64: risc-v: KASAN tag-based mode for
 x86

On 2/6/25 11:11, Christoph Lameter (Ampere) wrote:
> I also see that KASAN_HW_TAGS exist but this means that the tags can only
> be used with CONFIG_KASAN which is a kernel configuration for debug
> purposes.
> 
> What we are interested in is a *production* implementation with minimal
> software overhead that will be the default on ARM64 if the appropriate
> hardware is detected. 

Ahh, interesting. I'd assumed that once folks had in-hardware tag checks
that they'd just turn on CONFIG_KASAN and be happy.  Guess not!

> That in turn will hopefully allow other software instrumentation
> that is currently used to keep small objects secure and in turn
> creates overhead.
OK, so KASAN as-is is too broad. Are you saying that the kernel
_currently_ have "software instrumentation" like SLAB
redzoning/poisoning and you'd like to see MTE used to replace those?

Are you just interested in small objects?  What counts as small?  I
assume it's anything roughly <PAGE_SIZE.