linux-kernel - Re: [PATCH v4 00/18] kasan: x86: arm64: KASAN tag-based mode for x86

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Message-ID: <rbppxnzk5qcb3xn3gexennv3erveqdndxljytqe7bsbnfa4hd4@6zvjav6iuzhi>
Date: Fri, 22 Aug 2025 09:36:40 +0200
From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
To: Ada Couprie Diaz <ada.coupriediaz@....com>
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Subject: Re: [PATCH v4 00/18] kasan: x86: arm64: KASAN tag-based mode for x86

Hello, and thanks for testing the series!

On 2025-08-21 at 13:30:28 +0100, Ada Couprie Diaz wrote:
>Hi,
>
>On 12/08/2025 14:23, Maciej Wieczor-Retman wrote:
>> [...]
>> ======= Testing
>> Checked all the kunits for both software tags and generic KASAN after
>> making changes.
>> 
>> In generic mode the results were:
>> 
>> kasan: pass:59 fail:0 skip:13 total:72
>> Totals: pass:59 fail:0 skip:13 total:72
>> ok 1 kasan
>> 
>> and for software tags:
>> 
>> kasan: pass:63 fail:0 skip:9 total:72
>> Totals: pass:63 fail:0 skip:9 total:72
>> ok 1 kasan
>I tested the series on arm64 and after fixing the build issues mentioned
>I was able to boot without issues and did not observe any regressions
>in the KASAN KUnit tests with either generic or software tags.
>
>So this is Tested-by: Ada Couprie Diaz <ada.coupriediaz@....com> (For arm64)

Thank you! I'll try to send the fixed series on monday/tuesday.

>I will note that the tests `kmalloc_memmove_negative_size` and
>`kmalloc_memmove_invalid_size` seem to be able to corrupt memory
>and lead to kernel crashes if `memmove()` is not properly instrumented,
>which I discovered while investigating [0].

What do you mean by 'properly instrumented'? Is it the intrinsic prefix thing
for gcc that you mentioned?

>> [...]
>> ======= Compilation
>> Clang was used to compile the series (make LLVM=1) since gcc doesn't
>> seem to have support for KASAN tag-based compiler instrumentation on
>> x86.
>
>Interestingly, while investigating [0], this comment slipped by me and
>I managed to compile your series for x86 with software tags using GCC,
>though it is a bit hacky.
>You need to update the CC_HAS_KASAN_SW_TAGS to pass `-mlam=u48`
>or `-mlam=u57`, as it is disabled by default, and pass `-march=arrowlake`
>for compilation (the support for software tags depends on the arch).
>You could then test with GCC (though the issue in [0] also applies to x86).

Thanks! I'll try it out :)

>
>Best,
>Ada

-- 
Kind regards
Maciej Wieczór-Retman