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

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Message-ID: <aCx5v3h9snyI_Q9w@infradead.org>
Date: Tue, 20 May 2025 05:46:55 -0700
From: "hch@...radead.org" <hch@...radead.org>
To: "Xu, Lizhi" <Lizhi.Xu@...driver.com>
Cc: "hch@...radead.org" <hch@...radead.org>,
	Christian Hesse <mail@...rm.de>,
	"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

On Tue, May 20, 2025 at 12:27:44PM +0000, Xu, Lizhi wrote:
> isofs does not support read_iter (I used a directory when testing).
> 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,
> the problem will recur because isofs does not support write_iter.

All Linux filesystems do (or at least should) point read on directories
to generic_read_dir which returns -EISDIR as reading from directories
is not supported.