linux-kernel - Re: [PATCH] xfs: Fix xfs_dir2_sf_entry

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Date:   Thu, 9 Jan 2020 17:00:37 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Eric Sandeen <sandeen@...deen.net>, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: Fix xfs_dir2_sf_entry_t size check

Hi Darrick,

On 09/01/2020 16:50, Darrick J. Wong wrote:
> This sounds like gcc getting confused by the zero length array.  Though
> it's odd that randconfig breaks, but defconfig doesn't?  This sounds
> like one of the kernel gcc options causing problems.
>

This is what I started suspecting as well.

>>> 	/* size: 3, cachelines: 1, members: 3 */
>>> 	/* last cacheline: 3 bytes */
>>> };
>>>
>>> Can you please the same command on your machine, along with which arm abi is
>>> in use etc just for clarity?
>>>
>> The abi is arm32 eabihf. You can reproduce my scenario using randconfig with
>> seed 0x72F68201.
> Please send the actual .config file produced by randconfig 72f68201...
> 
>> In this case I get size 4, hence my patch.
>>
>> If I enable xfs on the defconfig though size is 3 accordingly to what you have
>> reported. I will continue the investigation.
> ...and the .config file produced by defconfig, in the hopes that someone
> will spot the culprit using differential analysis.  Assuming you haven't
> done that already.

I did not spot anything unusual yet. I am attaching the files so that someone
else can have a look in the meantime.

-- 
Regards,
Vincenzo

View attachment "def.config" of type "text/plain" (218275 bytes)

View attachment "rand.config" of type "text/plain" (113721 bytes)

Download attachment "pEpkey.asc" of type "application/pgp-keys" (14072 bytes)