linux-kernel - Re: [PATCH] vfs: ensure mount source is set to "none" if empty string specified

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Message-ID: <20240715-abgibt-akkreditieren-7ac23ec2413c@brauner>
Date: Mon, 15 Jul 2024 14:35:39 +0200
From: Christian Brauner <brauner@...nel.org>
To: Prakash Sangappa <prakash.sangappa@...cle.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	dhowells@...hat.com, viro@...iv.linux.org.uk
Subject: Re: [PATCH] vfs: ensure mount source is set to "none" if empty
 string specified

> The issue can be easily reproduced.
>  #mount -t tmpfs "" /tmp/tdir
>  #grep "/tmp/tdir" /proc/$$/mountinfo

The kernel has accepted "" before the new mount api was introduced. So
the regression was showing "none" when userspace requested "" which got
fixed. The patch proposed right here would reintroduce the regression:

(1) 4.15
    root@b1:~# cat /proc/self/mountinfo | grep mnt
    386 28 0:52 / /mnt rw,relatime shared:223 - tmpfs  rw

(2) 5.4
    root@f1:~# cat /proc/self/mountinfo | grep mnt
    584 31 0:55 / /mnt rw,relatime shared:336 - tmpfs none rw

(3) 6.10-rc6
    root@...alhost:~# cat /proc/self/mountinfo | grep mnt
    62 130 0:60 / /mnt rw,relatime shared:135 - tmpfs  rw,inode64