linux-kernel - Re: [PATCH v3 07/12] man/man2/fsmount.2: document "new" mount API

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: <1989d90de76.d3b8b3cc73065.2447955224950374755@zohomail.com>
Date: Tue, 12 Aug 2025 13:16:13 +0400
From: Askar Safin <safinaskar@...omail.com>
To: "Aleksa Sarai" <cyphar@...har.com>
Cc: "Alejandro Colomar" <alx@...nel.org>,
	"Michael T. Kerrisk" <mtk.manpages@...il.com>,
	"Alexander Viro" <viro@...iv.linux.org.uk>,
	"Jan Kara" <jack@...e.cz>,
	"G. Branden Robinson" <g.branden.robinson@...il.com>,
	"linux-man" <linux-man@...r.kernel.org>,
	"linux-api" <linux-api@...r.kernel.org>,
	"linux-fsdevel" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"David Howells" <dhowells@...hat.com>,
	"Christian Brauner" <brauner@...nel.org>
Subject: Re: [PATCH v3 07/12] man/man2/fsmount.2: document "new" mount API

fsmount:
> Unlike open_tree(2) with OPEN_TREE_CLONE, fsmount() can only be called once in the lifetime of a filesystem instance to produce a mount object.

I don't understand what you meant here. This phrase in its current form is wrong.
Consider this scenario: we did this:
fsopen(...)
fsconfig(..., FSCONFIG_SET_STRING, "source", ...)
fsconfig(..., FSCONFIG_CMD_CREATE, ...)
fsmount(...)
fsopen(...)
fsconfig(..., FSCONFIG_SET_STRING, "source", ...)
fsconfig(..., FSCONFIG_CMD_CREATE, ...)
fsmount(...)

We used FSCONFIG_CMD_CREATE here as opposed to FSCONFIG_CMD_CREATE_EXCL, thus
it is possible that second fsmount will return mount for the same superblock.
Thus that statement "fsmount() can only be called once in the lifetime of a filesystem instance to produce a mount object"
is not true.

--
Askar Safin
https://types.pl/@safinaskar