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Date:   Tue, 17 Oct 2023 12:05:49 +0100
From:   Lorenzo Stoakes <lstoakes@gmail.com>
To:     Sachin Sant <sachinp@linux.ibm.com>
Cc:     linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, linux-mm@kvack.org,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [powerpc] Kernel crash while running LTP (bisected)
Message-ID: <84a6c480-f29b-4a73-bbb0-4908145dc4db@lucifer.local>
References: <81C9E2C1-DCC3-4DDD-8466-069893398B5B@linux.ibm.com>
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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:
>
> [   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]
>
> Git bisect points to following patch
>
> commit 1db41d29b79ad271674081c752961edd064bbbac
>     mm: perform the mapping_map_writable() check after call_mmap()
>
> Reverting the patch allows the test to complete.
>
> - Sachin

Hi Sachin,

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.

[0]:https://lore.kernel.org/all/c9eb4cc6-7db4-4c2b-838d-43a0b319a4f0@lucifer.local/