Pass the largest possible namespace id as the cursor and check that
listns() fails with ENOENT instead of starting over:

- in the unified tree

- in a type-specific tree

- in the owner tree of the caller's user namespace

Nothing can come after the largest possible id.

Link: https://patch.msgid.link/20261021-work-mount-statmount_listns_fixes-v1-6-8917a4c1bd14@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Pull misc vfs updates from Christian Brauner:
 "Fixes:

   - aio: a keyed poll completion on an epoll instance could recurse
     into the same epoll waitqueue lock when the result eventfd is
     watched by that very instance. An unprivileged process could make a
     CPU spin on the recursive lock. eventfd-backed poll completions are
     always deferred now.

   - fsnotify_inoderemove() is only called once the inode is really
     dead, no nlink and no aliases, and open_by_handle_at() can't add an
     alias to a dead inode anymore. The race could crash fsnotify or
     lose inode mark notifications.

   - devtmpfs: the conversion of the public instance to ->get_tree()
     broke reconfiguring the shared superblock's options on later mounts
     which made the boot time defaults permanent. A reconfigure context
     is kept in fc->fs_private so the parse ops can forward options to
     the underlying filesystem.

   - ufs truncated the 64-bit directory size to an unsigned int in
     ufs_last_byte(). A crafted image with a 4 GiB directory produced an
     out-of-folio read in ufs_find_entry() and, with
     CONFIG_UFS_FS_WRITE, a write into an adjacent page.

   - devpts rejects max=0 instead of silently lifting the per-instance
     pty limit. The value wrapped into ida_alloc_max() and became
     unlimited.

   - fs_pin publishes pins with the rcu list helpers so the kill paths
     reading the lists under rcu see the initialization.

   - dentry_kill() reports a Tasks-RCU quiescent state. Its
     cond_resched() is the only reschedule point on the dentry teardown
     path and cond_resched() isn't a quiescent state for Tasks-RCU, so
     Meta kept seeing rcu_tasks stalls in btrfs subvolume deletion.

   - writeback sizes foreign flushes by the target wb's dirty pages
     instead of the memcg-wide count which over or undersized a single
     bdi flush.

   - nfsd READ emitted two fsnotify access events on the iterator path
     since vfs_iocb_iter_read() already sends one. A READ on a krb5i or
     krb5p mount showed up twice in inotify.

   - pipe and splice pass a poll key when waking readers and writers so
     epoll, poll() and select() waiters only wake for the event they
     asked for.

   - the iso8859-14 Unicode to charset tables had page01 duplicated as
     page1e so 29 code points mapped to the wrong bytes and 22 that
     aren't in the charset were accepted.

   - orangefs doesn't wait for an unmount service operation that never
     returns on system shutdown and uses ssize_t for strscpy() errors.

   - __register_chrdev() checks the kobject_set_name() return value.

   - selftest fixes: the openat2 tests hardcoded O_LARGEFILE to 0x8000
     which is O_NOFOLLOW on powerpc, resolve_test makes /tmp a
     mountpoint so RESOLVE_NO_XDEV has a boundary to trip over,
     file_stressor moves into its own directory with a 30 minute
     timeout, the kernfs listxattr test skips when SELinux exposes
     security.selinux, the namespaces active reference tests wait for
     the thread via a PIDFD_THREAD pidfd since pthread_join() returns
     before exit_nsproxy_namespaces(), the idmapped_tmpfile test chowns
     its directory into the mapped range, the clone3 CLONE_CLEAR_SIGHAND
     test adds CLONE_VM so it fails for the intended reason, the pidfd
     PPID error message prints the values it compares and fscontext_ns
     gets a .gitignore.

  Cleanups:

   - vmcore prints the release of the crashed kernel from the VMCOREINFO
     note so a kdump that dies before the dump lands still says which
     kernel it was for.

   - initramfs allocates hardlink hash entries with the validated cpio
     name length instead of PATH_MAX, which put every entry in
     kmalloc-8k.

   - the unused dax_layout_busy_page() is removed,
     dax_layout_busy_page_range() becomes static and dax_folio_init()
     drops a redundant list initialization.

   - vfs_empty_path() is removed, it has had no callers since
     getname_maybe_null().

   - comment and documentation fixes in aio, bpf_fs_kfuncs,
     fs-writeback, inode, read_write, squashfs and the vfs.rst copy of
     struct file_system_type"

* tag 'vfs-7.4-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (38 commits)
  selftests/filesystems: Fix idmapped_tmpfile layer dir ownership
  selftests/namespaces: Wait for thread exit via pidfd in active-ref tests
  writeback: size foreign flushes by target wb dirty pages
  initramfs: Reduce hardlink hash allocation sizes
  fs: remove unused vfs_empty_path()
  dcache: report a Tasks-RCU quiescent state in dentry_kill()
  vmcore: report the release of the crashed kernel
  splice: pass a poll key when waking pipe readers and writers
  pipe: pass a poll key when waking writers after a resize
  orangefs: use ssize_t instead of size_t for error codes...
  orangefs_super: don't wait on service operation on system shutdown.
  docs/vfs: Fix the struct file_system_type copy
  nls: fix the Unicode to charset tables of iso8859-14
  selftests/filesystems/openat2: make /tmp a mountpoint inside private namespace
  selftests/filesystems/openat2: fix O_LARGEFILE definitions for non-arm64 architectures
  fs: fix misleading comments in read_write.c
  squashfs: fix inode number description in documentation
  fs: fix typos in comments
  fs/dax: Make dax_layout_busy_page_range() static
  fs/dax: Remove unused dax_layout_busy_page()
  ...

pthread_join() returns once exit_mm() wakes the CLEARTID futex, but the
exiting thread drops its namespace reference later, in
exit_nsproxy_namespaces(). The joining thread can therefore still see the
namespace as active, making the final open_by_handle_at() check in
thread_ns_inactive_after_exit and thread_ns_fd_keeps_active fail
intermittently.

Have the thread open a PIDFD_THREAD pidfd on itself and poll it before
pthread_join(). A pidfd becomes readable from exit_notify(), which runs
after exit_nsproxy_namespaces().

Fixes: 29f083c49982 ("selftests/namespace: first threaded active reference count test")
Fixes: ee861032381b ("selftests/namespace: second threaded active reference count test")
Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
Link: https://patch.msgid.link/20261001-selftests-namespaces-nsid_race-v1-1-25f542cf0b9c@marliere.net
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Check that a uid_map or gid_map line with a value that does not fit in
u32, or with a negative value, is rejected with EINVAL and installs
nothing, for each of the three fields.

Check that in-range lines are still accepted and read back unchanged:
a plain single-id mapping, first id 0, the largest valid first id
4294967294, and a line with extra spaces between the fields. When run
as root in the initial user namespace, also check that the largest
count, "0 0 4294967295", is accepted when written by the parent into
the uid_map of a child namespace; an unprivileged writer can only map
a single id.

Signed-off-by: Natasha Klaus <natalie.klaus@runtimeverification.com>
Link: https://patch.msgid.link/20260930112854.373184-3-natalie.klaus@runtimeverification.com
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

In timens_separate and pidns_separate both the child and the grandchild
write a 'Y' readiness byte to the same pipe, but the parent expects a
single 'Y' followed by the grandchild's pid. If the grandchild's byte
arrives first, the parent takes it for the child's and reads the pid
misaligned, ending up with a garbage value.

The parent stores that pid in self->grandchild_pid so that
FIXTURE_TEARDOWN() can kill the grandchild. A garbage pid leaves the real
grandchild alive in pause(), holding the test runner's TAP pipe open and
hanging the whole collection.

The grandchild has nothing to report, so drop its write() and leave the
child as the sole writer.

Fixes: fdb48976b637 ("selftests/namespaces: Kill grandchild in nsid fixture teardown")
Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
Link: https://patch.msgid.link/20260810-selftests-namespaces_race-v1-1-4307e833783e@marliere.net
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

When listns() is not implemented the iterator child detects ENOSYS and
exits cleanly with status PIDFD_SKIP before the parent has a chance to
signal it.  The parent sends SIGKILL (which is a harmless no-op at that
point) and then calls waitpid(), obtaining a normal-exit status.  The
subsequent ASSERT_TRUE(WIFSIGNALED(status)) therefore fails, causing the
three EFAULT-focused tests to report FAIL rather than SKIP on kernels that
do not yet carry listns() support.

After collecting the iterator's exit status, check whether it exited with
PIDFD_SKIP and issue a SKIP verdict in that case, consistent with the
behaviour of every other listns test that already handles ENOSYS correctly.

Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://patch.msgid.link/20260407-selftests-namespaces_fixes-v1-3-59109909d88b@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

The efault tests spawn two categories of child processes: namespace
children (each in its own mount namespace, for concurrent destruction) and
an iterator child that calls listns() in a tight loop.  The cleanup loop
used waitpid(-1), which reaps any child in any order. If the iterator child
exits early (e.g. because listns() returned ENOSYS) before all namespace
children have been reaped, waitpid(-1) may consume it instead.  The
subsequent targeted waitpid(iter_pid) would then block indefinitely.

Track the PIDs of the namespace children explicitly and use targeted
waitpid() calls in the cleanup loop so the iterator child cannot be
inadvertently reaped during namespace cleanup.

Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://patch.msgid.link/20260407-selftests-namespaces_fixes-v1-2-59109909d88b@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

The timens_separate and pidns_separate test cases fork a grandchild that
calls pause().  FIXTURE_TEARDOWN only kills the direct child, which is the
init process of the grandchild's namespace.  Once the child (init) exits,
the grandchild is reparented to the host init but remains alive and
continues to hold the inherited write end of the test runner's TAP pipe
open.  tap_prefix never receives EOF and blocks indefinitely, hanging the
entire test collection.

Record the grandchild PID in the fixture struct so that teardown can send
SIGKILL and reap it before dealing with the child.  The grandchild must be
reaped first because the child acts as its PID namespace init; killing the
child first would kill the grandchild without giving us a chance to
waitpid() it.

Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://patch.msgid.link/20260407-selftests-namespaces_fixes-v1-1-59109909d88b@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Remove the inclusion of ../filesystems/utils.h from listns_efault_test.c.
The test doesn't use any symbols from that header. Including it alongside
../pidfd/pidfd.h causes a build failure because both headers define
wait_for_pid() with conflicting linkage:

  ../filesystems/utils.h:  extern int wait_for_pid(pid_t pid);
  ../pidfd/pidfd.h:        static inline int wait_for_pid(pid_t pid)

All symbols the test actually uses (create_child, read_nointr,
write_nointr, sys_pidfd_send_signal) come from pidfd.h.

Reported-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/all/acPV19IY3Gna6Ira@sirena.org.uk
Fixes: 07d7ad46dad4 ("selftests/namespaces: test for efault")
Signed-off-by: Christian Brauner <brauner@kernel.org>

Pull non-MM updates from Andrew Morton:

 - "panic: sys_info: Refactor and fix a potential issue" (Andy Shevchenko)
   fixes a build issue and does some cleanup in ib/sys_info.c

 - "Implement mul_u64_u64_div_u64_roundup()" (David Laight)
   enhances the 64-bit math code on behalf of a PWM driver and beefs up
   the test module for these library functions

 - "scripts/gdb/symbols: make BPF debug info available to GDB" (Ilya Leoshkevich)
   makes BPF symbol names, sizes, and line numbers available to the GDB
   debugger

 - "Enable hung_task and lockup cases to dump system info on demand" (Feng Tang)
   adds a sysctl which can be used to cause additional info dumping when
   the hung-task and lockup detectors fire

 - "lib/base64: add generic encoder/decoder, migrate users" (Kuan-Wei Chiu)
   adds a general base64 encoder/decoder to lib/ and migrates several
   users away from their private implementations

 - "rbree: inline rb_first() and rb_last()" (Eric Dumazet)
   makes TCP a little faster

 - "liveupdate: Rework KHO for in-kernel users" (Pasha Tatashin)
   reworks the KEXEC Handover interfaces in preparation for Live Update
   Orchestrator (LUO), and possibly for other future clients

 - "kho: simplify state machine and enable dynamic updates" (Pasha Tatashin)
   increases the flexibility of KEXEC Handover. Also preparation for LUO

 - "Live Update Orchestrator" (Pasha Tatashin)
   is a major new feature targeted at cloud environments. Quoting the
   cover letter:

      This series introduces the Live Update Orchestrator, a kernel
      subsystem designed to facilitate live kernel updates using a
      kexec-based reboot. This capability is critical for cloud
      environments, allowing hypervisors to be updated with minimal
      downtime for running virtual machines. LUO achieves this by
      preserving the state of selected resources, such as memory,
      devices and their dependencies, across the kernel transition.

      As a key feature, this series includes support for preserving
      memfd file descriptors, which allows critical in-memory data, such
      as guest RAM or any other large memory region, to be maintained in
      RAM across the kexec reboot.

   Mike Rappaport merits a mention here, for his extensive review and
   testing work.

 - "kexec: reorganize kexec and kdump sysfs" (Sourabh Jain)
   moves the kexec and kdump sysfs entries from /sys/kernel/ to
   /sys/kernel/kexec/ and adds back-compatibility symlinks which can
   hopefully be removed one day

 - "kho: fixes for vmalloc restoration" (Mike Rapoport)
   fixes a BUG which was being hit during KHO restoration of vmalloc()
   regions

* tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (139 commits)
  calibrate: update header inclusion
  Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()"
  vmcoreinfo: track and log recoverable hardware errors
  kho: fix restoring of contiguous ranges of order-0 pages
  kho: kho_restore_vmalloc: fix initialization of pages array
  MAINTAINERS: TPM DEVICE DRIVER: update the W-tag
  init: replace simple_strtoul with kstrtoul to improve lpj_setup
  KHO: fix boot failure due to kmemleak access to non-PRESENT pages
  Documentation/ABI: new kexec and kdump sysfs interface
  Documentation/ABI: mark old kexec sysfs deprecated
  kexec: move sysfs entries to /sys/kernel/kexec
  test_kho: always print restore status
  kho: free chunks using free_page() instead of kfree()
  selftests/liveupdate: add kexec test for multiple and empty sessions
  selftests/liveupdate: add simple kexec-based selftest for LUO
  selftests/liveupdate: add userspace API selftests
  docs: add documentation for memfd preservation via LUO
  mm: memfd_luo: allow preserving memfd
  liveupdate: luo_file: add private argument to store runtime state
  mm: shmem: export some functions to internal.h
  ...