linux-stable.git/fs/file_table.c, branch v6.9 Linux kernel stable tree Merge tag 'lsm-pr-20240312' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm 2024-03-13T03:03:34+00:00 Linus Torvalds torvalds@linux-foundation.org 2024-03-13T03:03:34+00:00 cc4a875cf3b3bc07d523ea85b8ca45da1ca4f4e6 Pull lsm updates from Paul Moore: - Promote IMA/EVM to a proper LSM This is the bulk of the diffstat, and the source of all the changes in the VFS code. Prior to the start of the LSM stacking work it was important that IMA/EVM were separate from the rest of the LSMs, complete with their own hooks, infrastructure, etc. as it was the only way to enable IMA/EVM at the same time as a LSM. However, now that the bulk of the LSM infrastructure supports multiple simultaneous LSMs, we can simplify things greatly by bringing IMA/EVM into the LSM infrastructure as proper LSMs. This is something I've wanted to see happen for quite some time and Roberto was kind enough to put in the work to make it happen. - Use the LSM hook default values to simplify the call_int_hook() macro Previously the call_int_hook() macro required callers to supply a default return value, despite a default value being specified when the LSM hook was defined. This simplifies the macro by using the defined default return value which makes life easier for callers and should also reduce the number of return value bugs in the future (we've had a few pop up recently, hence this work). - Use the KMEM_CACHE() macro instead of kmem_cache_create() The guidance appears to be to use the KMEM_CACHE() macro when possible and there is no reason why we can't use the macro, so let's use it. - Fix a number of comment typos in the LSM hook comment blocks Not much to say here, we fixed some questionable grammar decisions in the LSM hook comment blocks. * tag 'lsm-pr-20240312' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (28 commits) cred: Use KMEM_CACHE() instead of kmem_cache_create() lsm: use default hook return value in call_int_hook() lsm: fix typos in security/security.c comment headers integrity: Remove LSM ima: Make it independent from 'integrity' LSM evm: Make it independent from 'integrity' LSM evm: Move to LSM infrastructure ima: Move IMA-Appraisal to LSM infrastructure ima: Move to LSM infrastructure integrity: Move integrity_kernel_module_request() to IMA security: Introduce key_post_create_or_update hook security: Introduce inode_post_remove_acl hook security: Introduce inode_post_set_acl hook security: Introduce inode_post_create_tmpfile hook security: Introduce path_post_mknod hook security: Introduce file_release hook security: Introduce file_post_open hook security: Introduce inode_post_removexattr hook security: Introduce inode_post_setattr hook security: Align inode_setattr hook definition with EVM ... 
Pull lsm updates from Paul Moore:

 - Promote IMA/EVM to a proper LSM

   This is the bulk of the diffstat, and the source of all the changes
   in the VFS code. Prior to the start of the LSM stacking work it was
   important that IMA/EVM were separate from the rest of the LSMs,
   complete with their own hooks, infrastructure, etc. as it was the
   only way to enable IMA/EVM at the same time as a LSM.

   However, now that the bulk of the LSM infrastructure supports
   multiple simultaneous LSMs, we can simplify things greatly by
   bringing IMA/EVM into the LSM infrastructure as proper LSMs. This is
   something I've wanted to see happen for quite some time and Roberto
   was kind enough to put in the work to make it happen.

 - Use the LSM hook default values to simplify the call_int_hook() macro

   Previously the call_int_hook() macro required callers to supply a
   default return value, despite a default value being specified when
   the LSM hook was defined.

   This simplifies the macro by using the defined default return value
   which makes life easier for callers and should also reduce the number
   of return value bugs in the future (we've had a few pop up recently,
   hence this work).

 - Use the KMEM_CACHE() macro instead of kmem_cache_create()

   The guidance appears to be to use the KMEM_CACHE() macro when
   possible and there is no reason why we can't use the macro, so let's
   use it.

 - Fix a number of comment typos in the LSM hook comment blocks

   Not much to say here, we fixed some questionable grammar decisions in
   the LSM hook comment blocks.

* tag 'lsm-pr-20240312' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (28 commits)
  cred: Use KMEM_CACHE() instead of kmem_cache_create()
  lsm: use default hook return value in call_int_hook()
  lsm: fix typos in security/security.c comment headers
  integrity: Remove LSM
  ima: Make it independent from 'integrity' LSM
  evm: Make it independent from 'integrity' LSM
  evm: Move to LSM infrastructure
  ima: Move IMA-Appraisal to LSM infrastructure
  ima: Move to LSM infrastructure
  integrity: Move integrity_kernel_module_request() to IMA
  security: Introduce key_post_create_or_update hook
  security: Introduce inode_post_remove_acl hook
  security: Introduce inode_post_set_acl hook
  security: Introduce inode_post_create_tmpfile hook
  security: Introduce path_post_mknod hook
  security: Introduce file_release hook
  security: Introduce file_post_open hook
  security: Introduce inode_post_removexattr hook
  security: Introduce inode_post_setattr hook
  security: Align inode_setattr hook definition with EVM
  ...
file: add alloc_file_pseudo_noaccount() 2024-02-25T11:05:08+00:00 Christian Brauner brauner@kernel.org 2024-02-08T18:10:45+00:00 bac0a9e56e1fd14b227ab57142eca6f7bc6e6115 When we open block devices as files we want to make sure to not charge them against the open file limit of the caller as that can cause spurious failures. Link: https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-1-adbd023e19cc@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org> 
When we open block devices as files we want to make sure to not charge
them against the open file limit of the caller as that can cause
spurious failures.

Link: https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-1-adbd023e19cc@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
file: prepare for new helper 2024-02-25T11:04:13+00:00 Christian Brauner brauner@kernel.org 2024-02-08T18:08:37+00:00 0873add0e0cd74fe3c7dae3fcfd610cbc1d08bd1 In order to add a helper to open files that aren't accounted split alloc_file() and parts of alloc_file_pseudo() into helpers. One to prepare a path, another one to setup the file. Suggested-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20240129160241.GA2793@lst.de Signed-off-by: Christian Brauner <brauner@kernel.org> 
In order to add a helper to open files that aren't accounted split
alloc_file() and parts of alloc_file_pseudo() into helpers. One to
prepare a path, another one to setup the file.

Suggested-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240129160241.GA2793@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
ima: Move to LSM infrastructure 2024-02-16T04:43:46+00:00 Roberto Sassu roberto.sassu@huawei.com 2024-02-15T10:31:08+00:00 cd3cec0a02c7338ce2901c574f3935b8f6984aab Move hardcoded IMA function calls (not appraisal-specific functions) from various places in the kernel to the LSM infrastructure, by introducing a new LSM named 'ima' (at the end of the LSM list and always enabled like 'integrity'). Having IMA before EVM in the Makefile is sufficient to preserve the relative order of the new 'ima' LSM in respect to the upcoming 'evm' LSM, and thus the order of IMA and EVM function calls as when they were hardcoded. Make moved functions as static (except ima_post_key_create_or_update(), which is not in ima_main.c), and register them as implementation of the respective hooks in the new function init_ima_lsm(). Select CONFIG_SECURITY_PATH, to ensure that the path-based LSM hook path_post_mknod is always available and ima_post_path_mknod() is always executed to mark files as new, as before the move. A slight difference is that IMA and EVM functions registered for the inode_post_setattr, inode_post_removexattr, path_post_mknod, inode_post_create_tmpfile, inode_post_set_acl and inode_post_remove_acl won't be executed for private inodes. Since those inodes are supposed to be fs-internal, they should not be of interest to IMA or EVM. The S_PRIVATE flag is used for anonymous inodes, hugetlbfs, reiserfs xattrs, XFS scrub and kernel-internal tmpfs files. Conditionally register ima_post_key_create_or_update() if CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is enabled. Also, conditionally register ima_kernel_module_request() if CONFIG_INTEGRITY_ASYMMETRIC_KEYS is enabled. Finally, add the LSM_ID_IMA case in lsm_list_modules_test.c. Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> Acked-by: Chuck Lever <chuck.lever@oracle.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Christian Brauner <brauner@kernel.org> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Acked-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Paul Moore <paul@paul-moore.com> 
Move hardcoded IMA function calls (not appraisal-specific functions) from
various places in the kernel to the LSM infrastructure, by introducing a
new LSM named 'ima' (at the end of the LSM list and always enabled like
'integrity').

Having IMA before EVM in the Makefile is sufficient to preserve the
relative order of the new 'ima' LSM in respect to the upcoming 'evm' LSM,
and thus the order of IMA and EVM function calls as when they were
hardcoded.

Make moved functions as static (except ima_post_key_create_or_update(),
which is not in ima_main.c), and register them as implementation of the
respective hooks in the new function init_ima_lsm().

Select CONFIG_SECURITY_PATH, to ensure that the path-based LSM hook
path_post_mknod is always available and ima_post_path_mknod() is always
executed to mark files as new, as before the move.

A slight difference is that IMA and EVM functions registered for the
inode_post_setattr, inode_post_removexattr, path_post_mknod,
inode_post_create_tmpfile, inode_post_set_acl and inode_post_remove_acl
won't be executed for private inodes. Since those inodes are supposed to be
fs-internal, they should not be of interest to IMA or EVM. The S_PRIVATE
flag is used for anonymous inodes, hugetlbfs, reiserfs xattrs, XFS scrub
and kernel-internal tmpfs files.

Conditionally register ima_post_key_create_or_update() if
CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is enabled. Also, conditionally register
ima_kernel_module_request() if CONFIG_INTEGRITY_ASYMMETRIC_KEYS is enabled.

Finally, add the LSM_ID_IMA case in lsm_list_modules_test.c.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
security: Introduce file_release hook 2024-02-16T04:43:43+00:00 Roberto Sassu roberto.sassu@huawei.com 2024-02-15T10:31:01+00:00 f09068b5a114ed28d2df2e82a7d30dde0145dc69 In preparation for moving IMA and EVM to the LSM infrastructure, introduce the file_release hook. IMA calculates at file close the new digest of the file content and writes it to security.ima, so that appraisal at next file access succeeds. The new hook cannot return an error and cannot cause the operation to be reverted. Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> Acked-by: Christian Brauner <brauner@kernel.org> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Paul Moore <paul@paul-moore.com> 
In preparation for moving IMA and EVM to the LSM infrastructure, introduce
the file_release hook.

IMA calculates at file close the new digest of the file content and writes
it to security.ima, so that appraisal at next file access succeeds.

The new hook cannot return an error and cannot cause the operation to be
reverted.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Merge tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2024-01-12T04:11:35+00:00 Linus Torvalds torvalds@linux-foundation.org 2024-01-12T04:11:35+00:00 499aa1ca4eb6602df38afaecb88fc14edf50cdbb Pull dcache updates from Al Viro: "Change of locking rules for __dentry_kill(), regularized refcounting rules in that area, assorted cleanups and removal of weird corner cases (e.g. now ->d_iput() on child is always called before the parent might hit __dentry_kill(), etc)" * tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits) dcache: remove unnecessary NULL check in dget_dlock() kill DCACHE_MAY_FREE __d_unalias() doesn't use inode argument d_alloc_parallel(): in-lookup hash insertion doesn't need an RCU variant get rid of DCACHE_GENOCIDE d_genocide(): move the extern into fs/internal.h simple_fill_super(): don't bother with d_genocide() on failure nsfs: use d_make_root() d_alloc_pseudo(): move setting ->d_op there from the (sole) caller kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller retain_dentry(): introduce a trimmed-down lockless variant __dentry_kill(): new locking scheme d_prune_aliases(): use a shrink list switch select_collect{,2}() to use of to_shrink_list() to_shrink_list(): call only if refcount is 0 fold dentry_kill() into dput() don't try to cut corners in shrink_lock_dentry() fold the call of retain_dentry() into fast_dput() Call retain_dentry() with refcount 0 dentry_kill(): don't bother with retain_dentry() on slow path ... 
Pull dcache updates from Al Viro:
 "Change of locking rules for __dentry_kill(), regularized refcounting
  rules in that area, assorted cleanups and removal of weird corner
  cases (e.g. now ->d_iput() on child is always called before the parent
  might hit __dentry_kill(), etc)"

* tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits)
  dcache: remove unnecessary NULL check in dget_dlock()
  kill DCACHE_MAY_FREE
  __d_unalias() doesn't use inode argument
  d_alloc_parallel(): in-lookup hash insertion doesn't need an RCU variant
  get rid of DCACHE_GENOCIDE
  d_genocide(): move the extern into fs/internal.h
  simple_fill_super(): don't bother with d_genocide() on failure
  nsfs: use d_make_root()
  d_alloc_pseudo(): move setting ->d_op there from the (sole) caller
  kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller
  retain_dentry(): introduce a trimmed-down lockless variant
  __dentry_kill(): new locking scheme
  d_prune_aliases(): use a shrink list
  switch select_collect{,2}() to use of to_shrink_list()
  to_shrink_list(): call only if refcount is 0
  fold dentry_kill() into dput()
  don't try to cut corners in shrink_lock_dentry()
  fold the call of retain_dentry() into fast_dput()
  Call retain_dentry() with refcount 0
  dentry_kill(): don't bother with retain_dentry() on slow path
  ...
Merge tag 'sysctl-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux 2024-01-11T01:44:36+00:00 Linus Torvalds torvalds@linux-foundation.org 2024-01-11T01:44:36+00:00 a05aea98d4052dcd63d9d379613058e9e86c76d7 Pull sysctl updates from Luis Chamberlain: "To help make the move of sysctls out of kernel/sysctl.c not incur a size penalty sysctl has been changed to allow us to not require the sentinel, the final empty element on the sysctl array. Joel Granados has been doing all this work. In the v6.6 kernel we got the major infrastructure changes required to support this. For v6.7 we had all arch/ and drivers/ modified to remove the sentinel. For v6.8-rc1 we get a few more updates for fs/ directory only. The kernel/ directory is left but we'll save that for v6.9-rc1 as those patches are still being reviewed. After that we then can expect also the removal of the no longer needed check for procname == NULL. Let us recap the purpose of this work: - this helps reduce the overall build time size of the kernel and run time memory consumed by the kernel by about ~64 bytes per array - the extra 64-byte penalty is no longer inncurred now when we move sysctls out from kernel/sysctl.c to their own files Thomas Weißschuh also sent a few cleanups, for v6.9-rc1 we expect to see further work by Thomas Weißschuh with the constificatin of the struct ctl_table. Due to Joel Granados's work, and to help bring in new blood, I have suggested for him to become a maintainer and he's accepted. So for v6.9-rc1 I look forward to seeing him sent you a pull request for further sysctl changes. This also removes Iurii Zaikin as a maintainer as he has moved on to other projects and has had no time to help at all" * tag 'sysctl-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: sysctl: remove struct ctl_path sysctl: delete unused define SYSCTL_PERM_EMPTY_DIR coda: Remove the now superfluous sentinel elements from ctl_table array sysctl: Remove the now superfluous sentinel elements from ctl_table array fs: Remove the now superfluous sentinel elements from ctl_table array cachefiles: Remove the now superfluous sentinel element from ctl_table array sysclt: Clarify the results of selftest run sysctl: Add a selftest for handling empty dirs sysctl: Fix out of bounds access for empty sysctl registers MAINTAINERS: Add Joel Granados as co-maintainer for proc sysctl MAINTAINERS: remove Iurii Zaikin from proc sysctl 
Pull sysctl updates from Luis Chamberlain:
 "To help make the move of sysctls out of kernel/sysctl.c not incur a
  size penalty sysctl has been changed to allow us to not require the
  sentinel, the final empty element on the sysctl array. Joel Granados
  has been doing all this work.

  In the v6.6 kernel we got the major infrastructure changes required to
  support this. For v6.7 we had all arch/ and drivers/ modified to
  remove the sentinel. For v6.8-rc1 we get a few more updates for fs/
  directory only.

  The kernel/ directory is left but we'll save that for v6.9-rc1 as
  those patches are still being reviewed. After that we then can expect
  also the removal of the no longer needed check for procname == NULL.

  Let us recap the purpose of this work:

   - this helps reduce the overall build time size of the kernel and run
     time memory consumed by the kernel by about ~64 bytes per array

   - the extra 64-byte penalty is no longer inncurred now when we move
     sysctls out from kernel/sysctl.c to their own files

  Thomas Weißschuh also sent a few cleanups, for v6.9-rc1 we expect to
  see further work by Thomas Weißschuh with the constificatin of the
  struct ctl_table.

  Due to Joel Granados's work, and to help bring in new blood, I have
  suggested for him to become a maintainer and he's accepted. So for
  v6.9-rc1 I look forward to seeing him sent you a pull request for
  further sysctl changes. This also removes Iurii Zaikin as a maintainer
  as he has moved on to other projects and has had no time to help at
  all"

* tag 'sysctl-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux:
  sysctl: remove struct ctl_path
  sysctl: delete unused define SYSCTL_PERM_EMPTY_DIR
  coda: Remove the now superfluous sentinel elements from ctl_table array
  sysctl: Remove the now superfluous sentinel elements from ctl_table array
  fs: Remove the now superfluous sentinel elements from ctl_table array
  cachefiles: Remove the now superfluous sentinel element from ctl_table array
  sysclt: Clarify the results of selftest run
  sysctl: Add a selftest for handling empty dirs
  sysctl: Fix out of bounds access for empty sysctl registers
  MAINTAINERS: Add Joel Granados as co-maintainer for proc sysctl
  MAINTAINERS: remove Iurii Zaikin from proc sysctl
fs: Remove the now superfluous sentinel elements from ctl_table array 2023-12-28T12:57:57+00:00 Joel Granados j.granados@samsung.com 2023-11-21T11:35:12+00:00 9d5b9475356635d018b4d22f7e58fce32e2e89a7 This commit comes at the tail end of a greater effort to remove the empty elements at the end of the ctl_table arrays (sentinels) which will reduce the overall build time size of the kernel and run time memory bloat by ~64 bytes per sentinel (further information Link : https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/) Remove sentinel elements ctl_table struct. Special attention was placed in making sure that an empty directory for fs/verity was created when CONFIG_FS_VERITY_BUILTIN_SIGNATURES is not defined. In this case we use the register sysctl call that expects a size. Signed-off-by: Joel Granados <j.granados@samsung.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> 
This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

Remove sentinel elements ctl_table struct. Special attention was placed in
making sure that an empty directory for fs/verity was created when
CONFIG_FS_VERITY_BUILTIN_SIGNATURES is not defined. In this case we use the
register sysctl call that expects a size.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
fs: replace f_rcuhead with f_task_work 2023-12-12T13:24:13+00:00 Christian Brauner brauner@kernel.org 2023-11-30T12:49:09+00:00 372a34e66fb7f95124fadae9c600b231c35696a7 The naming is actively misleading since we switched to SLAB_TYPESAFE_BY_RCU. rcu_head is #define callback_head. Use callback_head directly and rename f_rcuhead to f_task_work. Add comments in there to explain what it's used for. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-3-e73ca6f4ea83@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org> 
The naming is actively misleading since we switched to
SLAB_TYPESAFE_BY_RCU. rcu_head is #define callback_head. Use
callback_head directly and rename f_rcuhead to f_task_work.

Add comments in there to explain what it's used for.

Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-3-e73ca6f4ea83@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>
file: massage cleanup of files that failed to open 2023-12-12T13:24:09+00:00 Al Viro viro@zeniv.linux.org.uk 2023-11-26T02:08:34+00:00 7cb537b6f6d7d6529be04139178f929d9a63b918 A file that has never gotten FMODE_OPENED will never have RCU-accessed references, its final fput() is equivalent to file_free() and if it doesn't have FMODE_BACKING either, it can be done from any context and won't need task_work treatment. Now that we have SLAB_TYPESAFE_BY_RCU we can simplify this and have other callers benefit. All of that can be achieved easier is to make fput() recoginze that case and call file_free() directly. No need to introduce a special primitive for that. It also allowed things like failing dentry_open() could benefit from that as well. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> [Christian Brauner <brauner@kernel.org>: massage commit message] Link: https://lore.kernel.org/r/20231126020834.GC38156@ZenIV Signed-off-by: Christian Brauner <brauner@kernel.org> 
A file that has never gotten FMODE_OPENED will never have RCU-accessed
references, its final fput() is equivalent to file_free() and if it
doesn't have FMODE_BACKING either, it can be done from any context and
won't need task_work treatment.

Now that we have SLAB_TYPESAFE_BY_RCU we can simplify this and have
other callers benefit. All of that can be achieved easier is to make
fput() recoginze that case and call file_free() directly.

No need to introduce a special primitive for that. It also allowed
things like failing dentry_open() could benefit from that as well.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[Christian Brauner <brauner@kernel.org>: massage commit message]
Link: https://lore.kernel.org/r/20231126020834.GC38156@ZenIV
Signed-off-by: Christian Brauner <brauner@kernel.org>