linux-kernel - Re: [PATCH v4] mm: x86: instrument __get/__put_kernel

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Message-ID: <CA+fCnZfQT3j=GpomTZU3pa-OiQXMOGX1tOpGdmdpMWy4a7XVEw@mail.gmail.com>
Date: Sat, 21 Sep 2024 22:49:15 +0200
From: Andrey Konovalov <andreyknvl@...il.com>
To: Sabyrzhan Tasbolatov <snovitoll@...il.com>
Cc: akpm@...ux-foundation.org, bp@...en8.de, brauner@...nel.org, 
	dave.hansen@...ux.intel.com, dhowells@...hat.com, dvyukov@...gle.com, 
	glider@...gle.com, hpa@...or.com, kasan-dev@...glegroups.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, mingo@...hat.com, 
	ryabinin.a.a@...il.com, tglx@...utronix.de, vincenzo.frascino@....com, 
	x86@...nel.org
Subject: Re: [PATCH v4] mm: x86: instrument __get/__put_kernel_nofault

On Sat, Sep 21, 2024 at 9:09 AM Sabyrzhan Tasbolatov
<snovitoll@...il.com> wrote:
>
> Instrument copy_from_kernel_nofault(), copy_to_kernel_nofault(),
> strncpy_from_kernel_nofault() where __put_kernel_nofault,
> __get_kernel_nofault macros are used.
>
> __get_kernel_nofault needs instrument_memcpy_before() which handles
> KASAN, KCSAN checks for src, dst address, whereas for __put_kernel_nofault
> macro, instrument_write() check should be enough as it's validated via
> kmsan_copy_to_user() in instrument_put_user().
>
> __get_user_size was appended with instrument_get_user() for KMSAN check in
> commit 888f84a6da4d("x86: asm: instrument usercopy in get_user() and
> put_user()") but only for CONFIG_CC_HAS_ASM_GOTO_OUTPUT.
>
> copy_from_to_kernel_nofault_oob() kunit test triggers 4 KASAN OOB
> bug reports as expected, one for each copy_from/to_kernel_nofault call.
>
> Reported-by: Andrey Konovalov <andreyknvl@...il.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=210505
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@...il.com>

I tried running the tests with this patch applied, but unfortunately
the added test fails on arm64, most likely due to missing annotations
in arm64 asm code.

We need to either mark the added test as x86-only via
KASAN_TEST_NEEDS_CONFIG_ON or add annotations for arm64.

With annotations for arm64, the test might still fail for other
architectures, but I think that's fine: hopefully relevant people will
add annotations in time. But I consider both x86 and arm64 important,
so we should keep the tests working there.

If you decide to add annotations for arm64, please also test both
KASAN_SW_TAGS and KASAN_HW_TAGS modes.

Thanks!