From: Rik van Riel <riel@surriel.com>
To: Nikola Ciprich <nikola.ciprich@linuxbox.cz>,
"Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, david@kernel.org,
Mike Rapoport <rppt@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Pedro Falcato <pfalcato@suse.de>,
Kiryl Shutsemau <kas@kernel.org>,
luizcap@redhat.com, pbonzini@redhat.com,
Borislav Petkov <bp@alien8.de>,
Tal Zussman <tz2294@columbia.edu>,
Matt Fleming <matt@readmodwrite.com>
Subject: Re: hunting memory corruption bug in 6.18.x
Date: Mon, 05 Oct 2026 07:25:38 -0400 [thread overview]
Message-ID: <bd8e9b01ad88cafb12da33331f32a1ce315f590b.camel@surriel.com> (raw)
In-Reply-To: <asKdhWiJb3qXeopz@pcnci.linuxbox.cz>
On Sun, 2026-10-04 at 20:40 +0200, Nikola Ciprich wrote:
> >
>
> crash> rd -64 0xffffb18905f60000 512
>
> ffffb18905f60430: 0000000000000000 0000000000000000
> ................
> ffffb18905f60440: 0fffffff0c930020 0000000000000000
> ...............
> ffffb18905f60450: 0fffffff0c930020 fffff86eb0c30000
> ...........n...
Two copies of the exact address you crashed on,
in a vmalloc area, presumably the dentry_hashtable?
Can you use vtop to check that the different occurrences
of the 0fffffff0c930020 address in the same vmalloc
area map to the pages you found in this crash dump?
>
> crash> rd -p 0x103360000 512
>
> 103360440: 0fffffff0c930020 0000000000000000
> ...............
> 103360450: 0fffffff0c930020 fffff86eb0c30000
> ...........n...
>
The same thing when reading the page directly.
So the invalid value the CPU reads is being read from
memory, and not hallucinated by the CPU.
> crash> search -p 0x0fffffff0c930020
> 103360440: fffffff0c930020
> 103360450: fffffff0c930020
> 114c32440: fffffff0c930020
> 114c32450: fffffff0c930020
> 1ae234400: fffffff0c930020
> 1ae234420: fffffff0c930020
> 1ae234430: fffffff0c930020
> 1ae234450: fffffff0c930020
> 24f0e2400: fffffff0c930020
> 24f0e2420: fffffff0c930020
> 24f0e2430: fffffff0c930020
> 24f0e2450: fffffff0c930020
> 342c40400: fffffff0c930020
> 342c40420: fffffff0c930020
> 342c40430: fffffff0c930020
> 342c40450: fffffff0c930020
> 77475b400: fffffff0c930020
> 77475b420: fffffff0c930020
> 77475b430: fffffff0c930020
> 77475b450: fffffff0c930020
> b2fabe400: fffffff0c930020
> b2fabe420: fffffff0c930020
> b2fabe430: fffffff0c930020
> b2fabe450: fffffff0c930020
> ea2d7c400: fffffff0c930020
> ea2d7c420: fffffff0c930020
> ea2d7c430: fffffff0c930020
> ea2d7c450: fffffff0c930020
> ef7a2d400: fffffff0c930020
> ef7a2d420: fffffff0c930020
> ef7a2d430: fffffff0c930020
> ef7a2d450: fffffff0c930020
> ef7a90400: fffffff0c930020
> ef7a90420: fffffff0c930020
> ef7a90430: fffffff0c930020
> ef7a90450: fffffff0c930020
> 10371fa400: fffffff0c930020
> 10371fa420: fffffff0c930020
> 10371fa430: fffffff0c930020
> 10371fa450: fffffff0c930020
These are not random offsets in the page,
either.
These all seem to be at offsets 0, 0x20,
0x30, 0x40, or 0x50 into the page.
If you look at the other addresses, are
there any that are not at one of these
offsets?
If this is a case of "system writes
fffffff0c930020 into one of 6 slots",
there could be some at offset 0x10
too.
I'm having AI comb the kernel now for
places where we could conceivably
construct this value, and write it
into one out of 6 slots.
>
--
All Rights Reversed.
next prev parent reply other threads:[~2026-10-05 11:25 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-25 8:48 Nikola Ciprich
2026-09-25 10:05 ` Lorenzo Stoakes (ARM)
2026-09-25 12:13 ` Lorenzo Stoakes (ARM)
2026-09-26 5:58 ` Nikola Ciprich
2026-09-26 9:32 ` Lorenzo Stoakes (ARM)
2026-09-28 9:05 ` Nikola Ciprich
2026-09-29 19:11 ` Nikola Ciprich
2026-09-30 9:07 ` Lorenzo Stoakes (ARM)
2026-09-30 18:40 ` Nikola Ciprich
2026-10-01 19:40 ` Nikola Ciprich
2026-10-01 22:21 ` David Laight
2026-10-02 9:50 ` Lorenzo Stoakes (ARM)
2026-10-02 14:55 ` Nikola Ciprich
2026-10-02 19:27 ` Lorenzo Stoakes (ARM)
2026-10-04 18:40 ` Nikola Ciprich
2026-10-05 11:25 ` Rik van Riel [this message]
2026-10-05 19:02 ` Nikola Ciprich
[not found] ` <20261005132113.43548696@pumpkin>
2026-10-05 19:25 ` Nikola Ciprich
2026-10-02 22:02 ` Borislav Petkov
2026-10-04 18:45 ` Nikola Ciprich
2026-10-05 10:58 ` Rik van Riel
2026-10-05 18:05 ` Nikola Ciprich
2026-09-26 16:02 ` Luiz Capitulino
2026-09-28 8:47 ` Nikola Ciprich
2026-10-04 22:20 ` Rik van Riel
2026-10-05 9:31 ` Nikola Ciprich
2026-10-05 8:31 ` Lance Yang
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