linux-kernel - Re: [PATCH] uapi: export PROCFS_ROOT

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] [day] [month] [year] [list]

Message-ID: <20250710-visuell-joghurt-c76814720040@brauner>
Date: Thu, 10 Jul 2025 09:39:29 +0200
From: Christian Brauner <brauner@...nel.org>
To: Aleksa Sarai <cyphar@...har.com>
Cc: Christian Brauner <brauner@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] uapi: export PROCFS_ROOT_INO

On Tue, 08 Jul 2025 23:21:51 +1000, Aleksa Sarai wrote:
> The root inode of /proc having a fixed inode number has been part of the
> core kernel ABI since its inception, and recently some userspace
> programs (mainly container runtimes) have started to explicitly depend
> on this behaviour.
> 
> The main reason this is useful to userspace is that by checking that a
> suspect /proc handle has fstype PROC_SUPER_MAGIC and is PROCFS_ROOT_INO,
> they can then use openat2(RESOLVE_{NO_{XDEV,MAGICLINK},BENEATH}) to
> ensure that there isn't a bind-mount that replaces some procfs file with
> a different one. This kind of attack has lead to security issues in
> container runtimes in the past (such as CVE-2019-19921) and libraries
> like libpathrs[1] use this feature of procfs to provide safe procfs
> handling functions.
> 
> [...]

Applied to the vfs-6.17.nsfs branch of the vfs/vfs.git tree.
Patches in the vfs-6.17.nsfs branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.17.nsfs

[1/1] uapi: export PROCFS_ROOT_INO
      https://git.kernel.org/vfs/vfs/c/76fdb7eb4e1c