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Subject: Re: [powerpc] Kernel crash while running LTP (bisected)
From:   Sachin Sant <sachinp@linux.ibm.com>
In-Reply-To: <84a6c480-f29b-4a73-bbb0-4908145dc4db@lucifer.local>
Date:   Tue, 17 Oct 2023 19:00:20 +0530
Cc:     linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, linux-mm@kvack.org,
        open list <linux-kernel@vger.kernel.org>
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Message-Id: <93251CB3-D144-44F5-A482-0051A398E643@linux.ibm.com>
References: <81C9E2C1-DCC3-4DDD-8466-069893398B5B@linux.ibm.com>
 <84a6c480-f29b-4a73-bbb0-4908145dc4db@lucifer.local>
To:     Lorenzo Stoakes <lstoakes@gmail.com>
Precedence: bulk


> On 17-Oct-2023, at 4:35=E2=80=AFPM, Lorenzo Stoakes =
<lstoakes@gmail.com> wrote:
>=20
> On Tue, Oct 17, 2023 at 02:46:07PM +0530, Sachin Sant wrote:
>> While running LTP tests (getpid02) on a Power10 server booted with
>> 6.6.0-rc6-next-20231016 following crash was seen:
>>=20
>> [   76.386628] Kernel attempted to read user page (d8) - exploit =
attempt? (uid: 0)
>> [   76.386649] BUG: Kernel NULL pointer dereference on read at =
0x000000d8
>> [   76.386653] Faulting instruction address: 0xc0000000004cda90
>> [   76.386658] Oops: Kernel access of bad area, sig: 11 [#1]
> [snip]
>>=20
>> Git bisect points to following patch
>>=20
>> commit 1db41d29b79ad271674081c752961edd064bbbac
>>    mm: perform the mapping_map_writable() check after call_mmap()
>>=20
>> Reverting the patch allows the test to complete.
>>=20
>> - Sachin
>=20
> Hi Sachin,
>=20
> Thanks for the report but this was triggered in another test =
previously and
> has been fixed already (apologies for the inconvenience!) see [0]. =
Andrew
> took the -fix patch and applied to mm-unstable, this should wend its =
way to
> -next in the meantime.

Ah, thank you. Yes the fix works for me.

- Sachin