linux-kernel - Re: [Cluster-devel] [BUG] fs: gfs2: possible null-pointer dereferences in gfs2_rgrp_bh

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Date:   Wed, 24 Jul 2019 17:08:47 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Steven Whitehouse <swhiteho@...hat.com>, rpeterso@...hat.com,
        agruenba@...hat.com
Cc:     cluster-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [Cluster-devel] [BUG] fs: gfs2: possible null-pointer
 dereferences in gfs2_rgrp_bh_get()

Thanks for the reply :)

On 2019/7/24 17:04, Steven Whitehouse wrote:
> Hi,
>
> On 24/07/2019 09:50, Jia-Ju Bai wrote:
>> In gfs2_rgrp_bh_get, there is an if statement on line 1191 to check 
>> whether "rgd->rd_bits[0].bi_bh" is NULL.
>
> That is how we detect whether the rgrp has already been read in, so 
> the function is skipped in the case that we've already read in the rgrp.
>
>
>> When "rgd->rd_bits[0].bi_bh" is NULL, it is used on line 1216:
>>     gfs2_rgrp_in(rgd, (rgd->rd_bits[0].bi_bh)->b_data);
>
> No it isn't. See line 1196 where bi_bh is set, and where we also bail 
> out (line 1198) in case it has not been set.
>

I overlooked the operation on line 1196...
Thanks for the pointer, I am sorry for the false report...


Best wishes,
Jia-Ju Bai