linux-kernel - Re: [PATCH V5] loop: Add sanity check for read/write

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Message-ID: <20250520144622.3fd9592a@leda.eworm.net>
Date: Tue, 20 May 2025 14:46:22 +0200
From: Christian Hesse <mail@...rm.de>
To: "Xu, Lizhi" <Lizhi.Xu@...driver.com>
Cc: "hch@...radead.org" <hch@...radead.org>, "axboe@...nel.dk"
 <axboe@...nel.dk>, "christian@...sel.eu" <christian@...sel.eu>,
 "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "ming.lei@...hat.com" <ming.lei@...hat.com>,
 "syzbot+6af973a3b8dfd2faefdc@...kaller.appspotmail.com"
 <syzbot+6af973a3b8dfd2faefdc@...kaller.appspotmail.com>,
 "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>
Subject: Re: [PATCH V5] loop: Add sanity check for read/write_iter

"Xu, Lizhi" <Lizhi.Xu@...driver.com> on Tue, 2025/05/20 12:27:
> If it is a regular file, generic_ro_fops is used. In this case,
> isofs supports read_iter. When a regular file has a writable attribute,

Just tested with an iso file where writable flag from loopback file inside
was explicitly removed. No change.

> the problem will recur because isofs does not support write_iter.

We have two indications here that setup should happen in read-only mode:

* The underlaying filesystem is read-only
* `losetup` is called with switch `--read-only`

I would expect both to make this happy.
-- 
Best regards,
Chris

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