[ Upstream commit 9b9e8bb81c41fd27e7b57a1c936fde140548535f ]

Having the parent directory locked protects entries from removal
by another thread, but it does *not* protect cursors from being
moved around by lseek() - or freed, for that matter.

Fixes: 6f6107640625 ("configfs: Introduce configfs_dirent_lock")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

[ Upstream commit 10da12d352b7b2bb330a8609fdda9a58bf0e9856 ]

Normally ->s_dentry is cleared when dentry it's pointing to becomes
negative (on eviction, realistically).  However, that only happens
if dentry gets to be positive in the first place; in case of inode
allocation failure dentry never becomes positive, so ->d_iput()
is not called at all.

We do part of what normally would've been done by configfs_d_iput()
(dropping the reference to configfs_dirent) manually, but we do
not clear ->s_dentry there.  Sloppy as it is, it does not matter in
case of configfs_create_{dir,link}() - there configfs_dirent does
not survive dropping the sole reference to it.

However, for configfs_lookup() it *does* survive, with a dangling
pointer to soon to be freed dentry sitting it its ->s_dentry.

Subsequent getdents(2) in that directory will end up dereferencing
that pointer in order to pick the inode number.  Use after free...

This is the minimal fix; the right approach is to set the linkage
between dentry and configfs_dirent only after we know that we have
an inode, but that takes more surgery and the bug had been there
since 2006, so...

Fixes: 3d0f89bb1694 ("configfs: Add permission and ownership to configfs objects") # 2.6.16-rc3
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Pull file->f_path constification from Al Viro:
 "Only one thing was modifying ->f_path of an opened file - acct(2).

  Massaging that away and constifying a bunch of struct path * arguments
  in functions that might be given &file->f_path ends up with the
  situation where we can turn ->f_path into an anon union of const
  struct path f_path and struct path __f_path, the latter modified only
  in a few places in fs/{file_table,open,namei}.c, all for struct file
  instances that are yet to be opened"

* tag 'pull-f_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (23 commits)
  Have cc(1) catch attempts to modify ->f_path
  kernel/acct.c: saner struct file treatment
  configfs:get_target() - release path as soon as we grab configfs_item reference
  apparmor/af_unix: constify struct path * arguments
  ovl_is_real_file: constify realpath argument
  ovl_sync_file(): constify path argument
  ovl_lower_dir(): constify path argument
  ovl_get_verity_digest(): constify path argument
  ovl_validate_verity(): constify {meta,data}path arguments
  ovl_ensure_verity_loaded(): constify datapath argument
  ksmbd_vfs_set_init_posix_acl(): constify path argument
  ksmbd_vfs_inherit_posix_acl(): constify path argument
  ksmbd_vfs_kern_path_unlock(): constify path argument
  ksmbd_vfs_path_lookup_locked(): root_share_path can be const struct path *
  check_export(): constify path argument
  export_operations->open(): constify path argument
  rqst_exp_get_by_name(): constify path argument
  nfs: constify path argument of __vfs_getattr()
  bpf...d_path(): constify path argument
  done_path_create(): constify path argument
  ...

Pull configfs update from Andreas Hindborg:
 "Just a very small refactoring to use PTR_ERR_OR_ZERO()"

* tag 'configfs-for-v6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/a.hindborg/linux:
  configfs: use PTR_ERR_OR_ZERO() to simplify code

... and get rid of path argument - it turns into a local variable in get_target()

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

generic_delete_inode() is rather misleading for what the routine is
doing. inode_just_drop() should be much clearer.

The new naming is inconsistent with generic_drop_inode(), so rename that
one as well with inode_ as the suffix.

No functional changes.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Use the standard error pointer macro to shorten the code and simplify.

Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20250812082709.49796-1-zhao.xichao@vivo.com
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

... to be used instead of manually assigning to ->s_d_op.
All in-tree filesystem converted (and field itself is renamed,
so any out-of-tree ones in need of conversion will be caught
by compiler).

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull non-MM updates from Andrew Morton:

 - "hung_task: extend blocking task stacktrace dump to semaphore" from
   Lance Yang enhances the hung task detector.

   The detector presently dumps the blocking tasks's stack when it is
   blocked on a mutex. Lance's series extends this to semaphores

 - "nilfs2: improve sanity checks in dirty state propagation" from
   Wentao Liang addresses a couple of minor flaws in nilfs2

 - "scripts/gdb: Fixes related to lx_per_cpu()" from Illia Ostapyshyn
   fixes a couple of issues in the gdb scripts

 - "Support kdump with LUKS encryption by reusing LUKS volume keys" from
   Coiby Xu addresses a usability problem with kdump.

   When the dump device is LUKS-encrypted, the kdump kernel may not have
   the keys to the encrypted filesystem. A full writeup of this is in
   the series [0/N] cover letter

 - "sysfs: add counters for lockups and stalls" from Max Kellermann adds
   /sys/kernel/hardlockup_count and /sys/kernel/hardlockup_count and
   /sys/kernel/rcu_stall_count

 - "fork: Page operation cleanups in the fork code" from Pasha Tatashin
   implements a number of code cleanups in fork.c

 - "scripts/gdb/symbols: determine KASLR offset on s390 during early
   boot" from Ilya Leoshkevich fixes some s390 issues in the gdb
   scripts

* tag 'mm-nonmm-stable-2025-05-31-15-28' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (67 commits)
  llist: make llist_add_batch() a static inline
  delayacct: remove redundant code and adjust indentation
  squashfs: add optional full compressed block caching
  crash_dump, nvme: select CONFIGFS_FS as built-in
  scripts/gdb/symbols: determine KASLR offset on s390 during early boot
  scripts/gdb/symbols: factor out pagination_off()
  scripts/gdb/symbols: factor out get_vmlinux()
  kernel/panic.c: format kernel-doc comments
  mailmap: update and consolidate Casey Connolly's name and email
  nilfs2: remove wbc->for_reclaim handling
  fork: define a local GFP_VMAP_STACK
  fork: check charging success before zeroing stack
  fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code
  fork: clean-up ifdef logic around stack allocation
  kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count
  kernel/watchdog: add /sys/kernel/{hard,soft}lockup_count
  x86/crash: make the page that stores the dm crypt keys inaccessible
  x86/crash: pass dm crypt keys to kdump kernel
  Revert "x86/mm: Remove unused __set_memory_prot()"
  crash_dump: retrieve dm crypt keys in kdump kernel
  ...