[PATCH v2 0/4] kernfs: three standalone fixes

[Shakeel Butt <shakeel.butt@linux.dev>]

Three independent kernfs fixes, plus selftest coverage for the paths
they touch.  The fixes do not depend on each other.

Patch 1 adds tests for decoding a file handle and for a rename that
keeps the same parent.  Patches 2-4:

 - kernfs_rename_ns() takes kernfs_rename_lock only when the parent
   changes, so two same-parent renames inside one
   kernfs_path_from_node() walk can build a path that never existed.
   sysfs_warn_dup() is the only caller that can see it.

 - __kernfs_fh_to_dentry() creates inodes with no lock, so a decode
   racing rmdir() can hash an inode after the removal's ilookup()
   pass.  The inode keeps i_nlink 1, so no IN_DELETE_SELF is sent.

 - kernfs_create_link() reads the target's uid and gid unlocked, so a
   chown in between gives the link an owner the target never had.

Patch 1 applies on top of the patch [1] ("selftests: cover kernfs
dentry revalidation") with vfs-7.4.kernfs branch in vfs tree as base.

[1] http://lore.kernel.org/20260902014050.499002-1-shakeel.butt@linux.dev

Changes since v1:
http://lore.kernel.org/20260903040253.670020-1-shakeel.butt@linux.dev
- Added cover letter
- Used approppriate tags
- Updated commit messages to be more concise
- Replaced data_race() with READ_ONCE() (TJ)

Shakeel Butt (4):
  selftests: cover kernfs file handles and same-parent rename
  kernfs: take kernfs_rename_lock for same-parent renames too
  kernfs: don't lose IN_DELETE_SELF when decoding a file handle
  kernfs: fix up the unlocked attribute reads on the creation paths

 fs/kernfs/dir.c                               |  40 ++-
 fs/kernfs/kernfs-internal.h                   |   9 +-
 fs/kernfs/mount.c                             |  32 +-
 fs/kernfs/symlink.c                           |  17 +-
 tools/testing/selftests/filesystems/config    |   1 +
 .../selftests/filesystems/kernfs_test.c       | 296 +++++++++++++++++-
 6 files changed, 362 insertions(+), 33 deletions(-)


base-commit: 47fc64fb3b433abb9f2242a85ba808ac6f87df22
-- 
2.53.0-Meta