linux-kernel - Re: [PATCH] proc: Move fdinfo PTRACE_MODE_READ check into the inode .permission operation

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Date: Thu,  2 May 2024 12:00:03 +0200
From: Christian Brauner <brauner@...nel.org>
To: Tyler Hicks <code@...icks.com>
Cc: Christian Brauner <brauner@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Kevin Parsons <parsonskev@...il.com>,
	stable@...r.kernel.org,
	Christian Koenig <christian.koenig@....com>,
	Jann Horn <jannh@...gle.com>,
	Kalesh Singh <kaleshsingh@...gle.com>,
	Hardik Garg <hargar@...ux.microsoft.com>,
	Allen Pais <apais@...ux.microsoft.com>
Subject: Re: [PATCH] proc: Move fdinfo PTRACE_MODE_READ check into the inode .permission operation

On Tue, 30 Apr 2024 19:56:46 -0500, Tyler Hicks wrote:
> The following commits loosened the permissions of /proc/<PID>/fdinfo/
> directory, as well as the files within it, from 0500 to 0555 while also
> introducing a PTRACE_MODE_READ check between the current task and
> <PID>'s task:
> 
>  - commit 7bc3fa0172a4 ("procfs: allow reading fdinfo with PTRACE_MODE_READ")
>  - commit 1927e498aee1 ("procfs: prevent unprivileged processes accessing fdinfo dir")
> 
> [...]

Hm, a bit unfortunate that this will mean we risk regressions by fixing a
regression. But this looks sane to me and having a permission handler for
fdinfo does seem like the more natural approach instead of doing the permission
check at open time.

---

Applied to the vfs.misc branch of the vfs/vfs.git tree.
Patches in the vfs.misc 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.misc

[1/1] proc: Move fdinfo PTRACE_MODE_READ check into the inode .permission operation
      https://git.kernel.org/vfs/vfs/c/0a960ba49869