linux-kernel - Re: [PATCH] vfs: relax linkat() AT_EMPTY_PATH - aka flink()

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Date: Fri, 12 Apr 2024 11:07:36 +0200
From: Christian Brauner <brauner@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Christian Brauner <brauner@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Lutomirski <luto@...nel.org>,
	Peter Anvin <hpa@...or.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] vfs: relax linkat() AT_EMPTY_PATH - aka flink() - requirements

On Wed, 10 Apr 2024 17:10:12 -0700, Linus Torvalds wrote:
>    "The definition of insanity is doing the same thing over and over
>     again and expecting different results”
> 
> We've tried to do this before, most recently with commit bb2314b47996
> ("fs: Allow unprivileged linkat(..., AT_EMPTY_PATH) aka flink") about a
> decade ago.
> 
> [...]

So it seems that this might be worth trying. I've picked up the patch
with two modifications:

(1) added the relaxed capability check.
(2) renamed the flag to LOOKUP_LINKAT_EMPTY
(3) slight adjustment to commit message

Should show up in -next if I don't hear objections or you want to apply
this directly. Fingers crossed we don't see regressions.

---

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] vfs: relax linkat() AT_EMPTY_PATH - aka flink() - requirements
      https://git.kernel.org/vfs/vfs/c/fa75d6e377fd