Re: [PATCH v2] fs/mnt_idmapping.c: Return -EINVAL when no map is written

From: Christian Brauner <brauner@kernel.org>
To: Taylor Jackson <taylor.a.jackson@me.com>
Cc: Christian Brauner <brauner@kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
	Seth Forshee <sforshee@kernel.org>
Subject: Re: [PATCH v2] fs/mnt_idmapping.c: Return -EINVAL when no map is written
Date: Thu,  8 Feb 2024 10:13:06 +0100	[thread overview]
Message-ID: <20240208-homogen-faszination-3740f9dc34b3@brauner> (raw)
In-Reply-To: <20240208-mnt-idmap-inval-v2-1-58ef26d194e0@me.com>

On Thu, 08 Feb 2024 03:02:54 +0000, Taylor Jackson wrote:
> Currently, it is possible to create an idmapped mount using a user
> namespace without any mappings. However, this yields an idmapped
> mount that doesn't actually map the ids. With the following change,
> it will no longer be possible to create an idmapped mount when using
> a user namespace with no mappings, and will instead return EINVAL,
> an “invalid argument” error code.
> 
> [...]

Thanks for the fix!
In case you're interested, it would be worth expanding
tool/testing/selftests/mount_setattr to verify that it's now impossible to use
an empty idmapping.

But note, that currently tool/testing/selftests/mount_setattr/ is broken
because the tests assume that tmpfs cannot be idmapped which hasn't been true
for a long 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] fs/mnt_idmapping.c: Return -EINVAL when no map is written
      https://git.kernel.org/vfs/vfs/c/b4291c7fd9e5