linux-kernel - Re: [powerpc] Kernel crash while running LTP (bisected)

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Message-Id: <93251CB3-D144-44F5-A482-0051A398E643@linux.ibm.com>
Date:   Tue, 17 Oct 2023 19:00:20 +0530
From:   Sachin Sant <sachinp@...ux.ibm.com>
To:     Lorenzo Stoakes <lstoakes@...il.com>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, linux-mm@...ck.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [powerpc] Kernel crash while running LTP (bisected)



> On 17-Oct-2023, at 4:35 PM, Lorenzo Stoakes <lstoakes@...il.com> wrote:
> 
> 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.

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

- Sachin