linux-kernel - Re: [PATCH] kmsan: Fix out-of-bounds access to shadow memory

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Message-ID: <20250910194921.GA3153735@google.com>
Date: Wed, 10 Sep 2025 19:49:21 +0000
From: Eric Biggers <ebiggers@...nel.org>
To: Alexander Potapenko <glider@...gle.com>, Marco Elver <elver@...gle.com>,
	kasan-dev@...glegroups.com
Cc: Dmitry Vyukov <dvyukov@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] kmsan: Fix out-of-bounds access to shadow memory

On Fri, Aug 29, 2025 at 09:45:00AM -0700, Eric Biggers wrote:
> Running sha224_kunit on a KMSAN-enabled kernel results in a crash in
> kmsan_internal_set_shadow_origin():
> 
>     BUG: unable to handle page fault for address: ffffbc3840291000
>     #PF: supervisor read access in kernel mode
>     #PF: error_code(0x0000) - not-present page
>     PGD 1810067 P4D 1810067 PUD 192d067 PMD 3c17067 PTE 0
>     Oops: 0000 [#1] SMP NOPTI
>     CPU: 0 UID: 0 PID: 81 Comm: kunit_try_catch Tainted: G                 N  6.17.0-rc3 #10 PREEMPT(voluntary)
>     Tainted: [N]=TEST
>     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
>     RIP: 0010:kmsan_internal_set_shadow_origin+0x91/0x100
>     [...]
>     Call Trace:
>     <TASK>
>     __msan_memset+0xee/0x1a0
>     sha224_final+0x9e/0x350
>     test_hash_buffer_overruns+0x46f/0x5f0
>     ? kmsan_get_shadow_origin_ptr+0x46/0xa0
>     ? __pfx_test_hash_buffer_overruns+0x10/0x10
>     kunit_try_run_case+0x198/0xa00

Any thoughts on this patch from the KMSAN folks?  I'd love to add
CONFIG_KMSAN=y to my crypto subsystem testing, but unfortunately the
kernel crashes due to this bug :-(

- Eric