linux-kernel - Re: [PATCH 1/2] block: Rework bio_for_each_segment

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Message-ID: <5ab59623-4317-5aff-5173-d7285b5b224c@squashfs.org.uk>
Date:   Fri, 31 Mar 2023 02:10:15 +0100
From:   Phillip Lougher <phillip@...ashfs.org.uk>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        willy@...radead.org, axboe@...nel.dk,
        Ming Lei <ming.lei@...hat.com>
Subject: Re: [PATCH 1/2] block: Rework bio_for_each_segment_all()

On 30/03/2023 19:59, Phillip Lougher wrote:
> On 30/03/2023 18:55, Kent Overstreet wrote:
>> On Wed, Mar 29, 2023 at 05:50:27PM +0100, Phillip Lougher wrote:
>>> There is a problem with the above code, on testing I get the following
>>> results:
>>>
>>> Index 78018785329, offset 49, bvec.bv_len 1024: In same bio, metadata 
>>> length
>>> 32780
>>
>> Could you share how you're doing your testing? I set up a basic test
>> (created images using every compression type, tested reading them) and
>> so far I'm not able to reproduce this.
> 
> I use a very large Squashfs file that triggers the edge case.
> 
> That is too big to post, and so I'll see if I can artifically generate
> a small Squashfs filesystem that triggers the edge case.
> 
> Phillip
> 
> 

Hi,

This is a Google drive link to a file that triggers the issue.

https://drive.google.com/file/d/1-3-a1BKq62hZGQ6ynioreMSWFMuCV9B4/view?usp=sharing

To reproduce the issue

% mount -t squashfs <the file> /mnt -o errors=panic

then either one of the following will produce a panic

% ls /mnt
% find /mnt -type f | xargs wc > /dev/null


Phillip