From: Tao Cui <cuitao@kylinos.cn>

Two small cleanups on the create_user_ns() and map_write() error
paths.  Both remove code that provably cannot have an effect; no
behavior change.

  user_namespace.c:164-167: the key_put() at fail_keyring has been
  dead since it was copy-pasted from free_user_ns() in 2016
  (dbec28460a89); persistent_keyring_register is only ever assigned
  lazily from key_get_persistent(), long after create_user_ns().

  user_namespace.c:1110-1112: the map clearing at the out: label of
  map_write() only ever zeroes an already-zero map; the destination
  map is untouched on every error path, and a second write to a
  mapped namespace is rejected before parsing.

Compile-tested and A/B-tested on next-20260827: identical behavior
on vanilla and patched kernels for single-write map failures,
recovery writes and 300 rounds of userns create/destroy.

Tao Cui (2):
  userns: remove dead key_put() on the create_user_ns() error path
  userns: don't clear the install target map on map_write() failure

 kernel/user_namespace.c | 6 ------
 1 file changed, 6 deletions(-)

-- 
2.43.0

On Fri, 28 Aug 2026 17:16:57 +0800, Tao Cui wrote:
> From: Tao Cui <cuitao@kylinos.cn>
> 
> Two small cleanups on the create_user_ns() and map_write() error
> paths.  Both remove code that provably cannot have an effect; no
> behavior change.
> 
>   user_namespace.c:164-167: the key_put() at fail_keyring has been
>   dead since it was copy-pasted from free_user_ns() in 2016
>   (dbec28460a89); persistent_keyring_register is only ever assigned
>   lazily from key_get_persistent(), long after create_user_ns().
> 
> [...]

Applied to the vfs-7.4.namespace branch of the vfs/vfs.git tree.
Patches in the vfs-7.4.namespace 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: master

[1/2] userns: remove dead key_put() on the create_user_ns() error path
      https://git.kernel.org/vfs/vfs/c/fec2c3c0744b