On Thu, Sep 11, 2025 at 10:51:45AM -0700, Eric Biggers wrote:
> On Thu, Sep 11, 2025 at 11:09:17AM +0200, Alexander Potapenko wrote:
> > On Wed, Sep 10, 2025 at 9:49 PM Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
> > >
> > > 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
> >
> > Sorry, I was out in August and missed this email when digging through my inbox.
> >
> > Curiously, I couldn't find any relevant crashes on the KMSAN syzbot
> > instance, but the issue is legit.
> > Thank you so much for fixing this!
> >
> > Any chance you can add a test case for it to mm/kmsan/kmsan_test.c?
>
> Unfortunately most of the KMSAN test cases already fail on upstream,
> which makes it difficult to develop new ones:
The KMSAN test failures bisect to the following commit:
commit f90b474a35744b5d43009e4fab232e74a3024cae
Author: Vlastimil Babka <vbabka@xxxxxxx>
Date: Mon Mar 10 13:40:17 2025 +0100
mm: Fix the flipped condition in gfpflags_allow_spinning()
I'm not sure why. Apparently something related to lib/stackdepot.c.
Reverting that commit on top of upstream fixes the KMSAN tests.
- Eric
