[GIT PULL] fs fix for v5.19-rc3

[GIT PULL] fs fix for v5.19-rc3

[Christian Brauner]

Hey Linus,

/* Summary */
This fixes an issue where we fail to change the group of a file when the caller
owns the file and is a member of the group to change to. This is only relevant
on idmapped mounts. This has originally been reported against [2]. There's a
detailed description in the commit message and regression tests have been added
to xfstests at [1].

Link: https://lore.kernel.org/fstests/20220615092826.2333847-1-brauner@kernel.org [1]
Link: Link: https://github.com/lxc/lxd/issues/10537 [2]

/* Testing */
All patches are based on v5.19-rc1 and have been sitting in linux-next. No
build failures or warnings were observed. The fstests, ltp, and associated
selftests pass without regressions.

/* Conflicts */
At the time of creating this PR no merge conflicts were reported from
linux-next and no merge conflicts showed up doing a test-merge with current
mainline.

The following changes since commit f2906aa863381afb0015a9eb7fefad885d4e5a56:

  Linux 5.19-rc1 (2022-06-05 17:18:54 -0700)

are available in the Git repository at:

  git@gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux tags/fs.fixes.v5.19-rc3

for you to fetch changes up to 168f912893407a5acb798a4a58613b5f1f98c717:

  fs: account for group membership (2022-06-14 12:18:47 +0200)

Please consider pulling these changes from the signed fs.fixes.v5.19-rc3 tag.

Thanks!
Christian

----------------------------------------------------------------
fs.fixes.v5.19-rc3

----------------------------------------------------------------
Christian Brauner (1):
      fs: account for group membership

 fs/attr.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

Re: [GIT PULL] fs fix for v5.19-rc3

[pr-tracker-bot]

The pull request you sent on Wed, 15 Jun 2022 12:37:52 +0200:

> git@gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux tags/fs.fixes.v5.19-rc3

has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/979086f5e0066b4eff66e1eee123da228489985c

Thank you!

-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/prtracker.html

Re: [GIT PULL] fs fix for v5.19-rc3

[Linus Torvalds]

On Wed, Jun 15, 2022 at 3:39 AM Christian Brauner <brauner@kernel.org> wrote:
>
> This fixes an issue where we fail to change the group of a file when the caller
> owns the file and is a member of the group to change to. This is only relevant
> on idmapped mounts.

Pulled, but this code makes me go "Eww".

I do get the feeling that maybe we should have some kind of static
type help here, with "unmapped" and "filesystem mapped" uid/gid values
having different types, the same way we have kuid_t vs uid_t for
user-namespace mapping.

Because it feels like the problem here is that "kgid_t" has different
meanings depending on context.

In fact, just within that one function, we have *three* very different kgid_t's:

 - the argument to the function is a "kgid_t gid", which has *not*
been mapped into the filesystem mapping (why not?)

 - the function itself declares a "kgid_t kgid", which is the inode
group ID mapped into the mount

 - it how additionally has that thied "kgid_t mapped_gid", which is
the first 'gid' mapped into the mount

and honestly, I find that hugely confusing. The naming doesn't exactly
clarify things either (ie "gid" is a "kgid_t", not a "git_t", and so
is "kgid" - not helpful).

And being confusing with no type system support isn't a great thing.

So I'm wondering if <linux/mnt_idmapping.h> might be able to do the
same kind of things we do in <linux/uidgid.h>.

NOTE: I did not look into just how hugely painful that would be. Maybe
the above is the rantings of a madman.

              Linus

Re: [GIT PULL] fs fix for v5.19-rc3

[Christian Brauner]

On Wed, Jun 15, 2022 at 09:31:32AM -0700, Linus Torvalds wrote:
> On Wed, Jun 15, 2022 at 3:39 AM Christian Brauner <brauner@kernel.org> wrote:
> >
> > This fixes an issue where we fail to change the group of a file when the caller
> > owns the file and is a member of the group to change to. This is only relevant
> > on idmapped mounts.
> 
> Pulled, but this code makes me go "Eww".
> 
> I do get the feeling that maybe we should have some kind of static
> type help here, with "unmapped" and "filesystem mapped" uid/gid values
> having different types, the same way we have kuid_t vs uid_t for
> user-namespace mapping.
> 
> Because it feels like the problem here is that "kgid_t" has different
> meanings depending on context.
> 
> In fact, just within that one function, we have *three* very different kgid_t's:
> 
>  - the argument to the function is a "kgid_t gid", which has *not*
> been mapped into the filesystem mapping (why not?)
> 
>  - the function itself declares a "kgid_t kgid", which is the inode
> group ID mapped into the mount
> 
>  - it how additionally has that thied "kgid_t mapped_gid", which is
> the first 'gid' mapped into the mount
> 
> and honestly, I find that hugely confusing. The naming doesn't exactly
> clarify things either (ie "gid" is a "kgid_t", not a "git_t", and so
> is "kgid" - not helpful).
> 
> And being confusing with no type system support isn't a great thing.
> 
> So I'm wondering if <linux/mnt_idmapping.h> might be able to do the
> same kind of things we do in <linux/uidgid.h>.
> 
> NOTE: I did not look into just how hugely painful that would be. Maybe
> the above is the rantings of a madman.

I'm actually looking into this and have been for a while. I had thought
about this from the start but just now have time to play with this!