Re: [PATCH 0/8] creds: add {scoped_}with_kernel_creds()

[Jens Axboe <axboe@kernel.dk>]

On 11/2/25 4:12 PM, Christian Brauner wrote:
> Hey,
> 
> A few months ago I did work to make override_creds()/revert_creds()
> completely reference count free - mostly for the sake of
> overlayfs but it has been beneficial to everyone using this.
> 
> In a recent pull request from Jens that introduced another round of
> override_creds()/revert_creds() for nbd Linus asked whether we could
> avoide the prepare_kernel_creds() calls that duplicate the kernel
> credentials and then drop them again later.
> 
> Yes, we can actually. We can use the guard infrastructure to completely
> avoid the allocation and then also to never expose the temporary
> variable to hold the kernel credentials anywhere in the callers.
> 
> So add with_kernel_creds() and scoped_with_kernel_creds() for this
> purpose. Also take the opportunity to fixup the scoped_class() macro I
> introduced two cycles ago.
> 
> I've put this into kernel-6.19.cred now. Linus, not sure if you're
> paying attention but if you want you can give this a final look.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>
> ---
> Christian Brauner (8):
>       cleanup: fix scoped_class()
>       cred: add kernel_cred() helper
>       cred: make init_cred static
>       cred: add {scoped_}with_kernel_creds
>       firmware: don't copy kernel creds
>       nbd: don't copy kernel creds
>       target: don't copy kernel creds
>       unix: don't copy creds
> 
>  drivers/base/firmware_loader/main.c   | 59 +++++++++++++++--------------------
>  drivers/block/nbd.c                   | 17 ++--------
>  drivers/target/target_core_configfs.c | 14 ++-------
>  include/linux/cleanup.h               | 15 ++++-----
>  include/linux/cred.h                  | 18 +++++++++++
>  include/linux/init_task.h             |  1 -
>  init/init_task.c                      | 27 ++++++++++++++++
>  kernel/cred.c                         | 27 ----------------
>  net/unix/af_unix.c                    | 17 +++-------
>  security/keys/process_keys.c          |  2 +-
>  10 files changed, 87 insertions(+), 110 deletions(-)

Looks good to me, and love diffstats like that:

Reviewed-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe