linux-kernel - Re: [PATCH V3] loop: Add sanity check for read/write

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aA95UNX_BHq7GtP9@infradead.org>
Date: Mon, 28 Apr 2025 05:49:20 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Lizhi Xu <lizhi.xu@...driver.com>
Cc: hch@...radead.org, axboe@...nel.dk, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, ming.lei@...hat.com,
	syzbot+6af973a3b8dfd2faefdc@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V3] loop: Add sanity check for read/write_iter

On Sat, Apr 26, 2025 at 10:10:55AM +0800, Lizhi Xu wrote:
> +static int loop_check_backing_file(struct file *file, blk_mode_t mode, bool change)
> +{
> +	if (!file->f_op->read_iter)
> +		return -EINVAL;
> +
> +	if (((file->f_mode & FMODE_WRITE) ||
> +	     (!change && (mode & BLK_OPEN_WRITE))) &&
> +	    (!file->f_op->write_iter))
> +		return -EINVAL;

This looks a bit odd.  Both callers have the open struct file, so
we should be able to check f_mode for both cases and not need the
change flag as far as I can tell.  Or did I miss something/

If for some reason we could not pass the fmode, the helper is
probably not all that useful.