Pull bootconfig fixes from Masami Hiramatsu:
 "Fix integer overflow and truncation in size checks.

   - Fix size check bypasses caused by integer overflow and truncation
     when parsing initrd or standalone bootconfig files, preventing
     buffer overflow and out-of-bounds writes in the userspace tool.

   - Fix pointer arithmetic wrap-around in get_boot_config_from_initrd()
     when handling crafted huge size values, preventing fatal kernel
     page faults during early boot"

* tag 'bootconfig-fixes-v7.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  bootconfig: Fix integer overflow in initrd size check
  tools/bootconfig: Fix integer overflow and truncation in size checks

Sashiko reported that in get_boot_config_from_initrd(), a crafted initrd
with a huge bootconfig size (such as 0xFFFFFFFF) can cause the pointer
arithmetic:

    data = ((void *)hdr) - size;

to wrap around on 32-bit systems (or when pointer subtraction overflows).
Because data wraps around, the subsequent bounds check:

    if ((unsigned long)data < initrd_start)

evaluates to false, bypassing the check. The kernel then calls
xbc_calc_checksum(data, size), which attempts to read 4GB of memory,
hitting unmapped pages and triggering a fatal kernel page fault during
early boot. Furthermore, on 64-bit systems with an initrd > 4.29 GB, an
unbounded 32-bit size can similarly bypass the initrd_start check.

Fix this by:
1. Ensuring the initrd is at least large enough to contain the bootconfig
   footer and verifying hdr is within the initrd bounds.
2. Checking that size does not exceed XBC_DATA_MAX and does not exceed
   the available space between initrd_start and hdr before performing
   pointer subtraction.

Link: https://lore.kernel.org/all/178905333479.213925.1358412668943562406.stgit@devnote2/

Fixes: de462e5f1071 ("bootconfig: Fix to remove bootconfig data from initrd while boot")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260910010137.EE0431F000FF@smtp.kernel.org/
Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Sang-Heon Jeon <ekffu200098@gmail.com>

Pull vfs fixes from Christian Brauner:

 - netfs:

     - Fix an uninitialized return value in netfs_unbuffered_write()
       when preparing the first subrequest fails

     - For partial unbuffered/DIO writes return the amount transferred
       rather than an error

     - Update i_size with the amount actually written when a partial
       transfer ends in an error

     - Fix a subrequest reference leak when the io_iter ends up empty

     - Handle netfs_alloc_subrequest() failure during unbuffered writes

     - Load all readahead folios into the rolling buffer upfront and
       drop the readahead references once the first subrequest is
       dispatched

     - Mark folios for copy-to-cache while issuing subrequests

     - Fix read progress reporting

 - afs:

     - Add the missing kunmap in the error path of afs_dir_search_bucket()

     - Fix a double kunmap in afs_edit_dir_remove()

     - Don't free an existing server's endpoint state when cleaning up a
       candidate server in afs_lookup_server()

     - Unbind peers removed from a server's address list

 - ufs:

     - Load the cylinder group metadata before creating the root dentry

     - Validate the cylinder group index and rotor positions before
       caching them

     - Treat an unreadable directory block as not empty

 - exec:

     - Close the close-on-exec files before taking exec_update_lock

       Closing a file can block on the filesystem, so a hung filesystem
       blocked everything that takes exec_update_lock and a FUSE server
       inspecting the calling process could deadlock

     - Drop the bprm loader before closing bprm->file in free_bprm()

 - exit: Hold a reference to thread_pid across proc_flush_pid()

 - reboot: Fix a use-after-free on cad_pid

 - nsfs: Keep the namespace tree fields out of the rcu_head used by
   kfree_rcu()

 - nstree: Check listing permission before taking a namespace
   reference in listns()

 - super: Return 0 when a nested thaw drops its hold while other
   freezers remain

 - ext4: Don't set I_METADATA_WRITEBACK during fastcommit replay

 - adfs: Free s_fs_info in ->kill_sb()

 - autofs: Free the inode info allocated in autofs_fill_super() when
   the root inode allocation fails

 - ovl: Return EINVAL instead of EIO on a user namespace mismatch now
   that it's a plain refusal and not an internal error

 - cachefiles: Don't cast the variable-length coherency data to a
   __be64 in the coherency tracepoint

* tag 'vfs-7.3-rc3.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (28 commits)
  nstree: check listing permission before taking a namespace reference
  exec: do_close_on_exec() before taking exec_update_lock
  exit: hold a reference to thread_pid across proc_flush_pid
  fs: autofs: fix memory leak in autofs_fill_super()
  exec: Drop bprm loader before closing bprm->file
  afs: Clear stale peer app data after address list changes
  afs: Fix incorrect free in candidate cleanup in afs_lookup_server()
  afs: Fix double-unmap of directory block
  afs: Fix missing kunmap in afs_dir_search_bucket()
  ovl: return EINVAL instead of EIO in case of mismatched user_ns
  reboot: fix cad_pid use-after-free race
  cachefiles: Fix potential UAF/KASAN warning
  netfs: Fix read progress reporting
  netfs: Mark folios with COPY_TO_CACHE whilst issuing subreqs
  netfs: Fix readahead synchronisation issues by loading all folios upfront
  netfs: break unbuffered write when netfs_alloc_subrequest() fails
  netfs: Fix subreq ref leak
  netfs: Fix i_size update for partial transfer
  netfs: Fix error vs transferred passed to ->ki_complete()
  netfs: Fix unbuffered/DIO write partial transfer error return
  ...

cad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid()
reads it and passes it to pid_vnr() without protecting the lifetime of
the referenced struct pid. A concurrent writer can replace cad_pid and
drop the final reference to the old struct pid after the reader has
loaded the pointer but before pid_vnr() has finished dereferencing it,
causing a use-after-free.

kill_cad_pid() has the same lifetime race when it passes cad_pid to
kill_pid().

At the time this issue was reported, an unprivileged user could reach the
sysctl through user and PID namespaces because cad_pid was registered in
pid_table[]. Moving cad_pid back to the global reboot sysctl table
corrected that namespace and permission mismatch, but did not fix the
underlying lifetime race.

Fix this by treating cad_pid as an RCU-protected pointer at both read
sites and by waiting for a grace period before dropping the old reference
on the write side.

call_rcu(&old_pid->rcu, ...) cannot be used here because free_pid()
also queues pid->rcu; queueing the same rcu_head twice can corrupt the
RCU callback list.

Original KASAN crash stack:
  kernel/pid.c:545 pid_nr_ns()        # reads freed pid->level
  kernel/pid.c:556 pid_vnr()          # calls pid_nr_ns()
  kernel/pid.c:775 proc_do_cad_pid()  # calls pid_vnr(cad_pid)

Fixes: 9ec52099e4b8 ("[PATCH] replace cad_pid by a struct pid")
Reported-by: AutonomousCodeSecurity@microsoft.com
Closes: https://lore.kernel.org/all/20260717210143.4734-1-blbllhy@gmail.com/
Link: https://lore.kernel.org/all/alz5ZYLE4kaq_v2P@redhat.com/
Link: https://lore.kernel.org/all/al4ICz9biJKtdZc4@redhat.com/
Suggested-by: Mateusz Guzik <mjguzik@gmail.com>
Suggested-by: Bradley Morgan <include@grrlz.net>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Suggested-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: stable@vger.kernel.org
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Link: https://patch.msgid.link/20260814040944.16561-1-blbllhy@gmail.com
Reviewed-by: Bradley Morgan <include@grrlz.net>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Pull bootconfig updates from Masami Hiramatsu:

 - Support build-time command line building for embedded bootconfig

 - Fix xbc_snprint_cmdline() to render descendant keys when the root has
   both a value and subkeys, and treats empty subtrees correctly.

 - Add build-time pipeline using tools/bootconfig -C to render the
   embedded bootconfig "kernel" subtree into .init.rodata as a cmdline
   string.

 - Clean build-time tools/bootconfig from make clean

 - Add helper to prepend embedded bootconfig cmdline into
   boot_command_line early before parse_early_param()

 - Wire early prepend helper in x86 setup_arch() so early_param handlers
   see values from the embedded bootconfig (currently x86 only)

 - Avoid duplicating "kernel" keys in setup_boot_config()

 - Refactor setup_boot_config() to share bootconfig_cmdline_requested()

 - Document CONFIG_CMDLINE_FROM_BOOTCONFIG usage, requirements, and
   precedence

* tag 'bootconfig-v7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  init/main.c: use bootconfig_cmdline_requested() for the runtime opt-in
  bootconfig: skip runtime kernel.* render once prepended early
  x86/setup: prepend embedded bootconfig cmdline before parse_early_param
  Documentation: bootconfig: document build-time cmdline rendering
  bootconfig: add xbc_prepend_embedded_cmdline() helper
  bootconfig: clean build-time tools/bootconfig from make clean
  bootconfig: render embedded bootconfig as a kernel cmdline at build time
  bootconfig: render descendant keys when xbc_snprint_cmdline() root has a value

setup_boot_config() open-coded the same "is bootconfig requested on the
kernel command line?" check that setup_arch() performs via the shared
bootconfig_cmdline_requested() helper. Switch it to the helper so the
early (setup_arch) and late (setup_boot_config) paths use one parser and
cannot disagree on what counts as opt-in.

The helper also reports the offset of the init arguments following a "--"
separator, which is exactly what initargs_offs needs, so the local
parse_args() call, its bootconfig_params() callback and the tmp_cmdline
copy are removed.

No functional change intended.

Link: https://lore.kernel.org/all/20260626-bootconfig_using_tools-v7-9-24ab72139c29@debian.org/

Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

setup_boot_config() folds the embedded bootconfig "kernel" subtree into
the command line via xbc_make_cmdline("kernel"). A subsequent patch lets
an architecture prepend the build-time-rendered embedded "kernel" keys
to boot_command_line early in setup_arch(); rendering them again here
would then duplicate every key in saved_command_line and make
accumulating handlers (console=, earlycon=, ...) re-register the same
value.

Track whether the bootconfig data came from the embedded source
(from_embedded) and skip the runtime render only when the early prepend
actually happened, as reported by xbc_embedded_cmdline_applied(). On
architectures that do not select ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
that helper is a stub returning false, so this path is unchanged and the
embedded "kernel" keys still reach the cmdline via the runtime parser
exactly as before.

Link: https://lore.kernel.org/all/20260626-bootconfig_using_tools-v7-8-24ab72139c29@debian.org/

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Spawn kernel_init (PID 1) via kernel_clone() directly instead of
user_mode_thread(), without CLONE_FS. This gives PID 1 its own private
copy of init_task's fs_struct rather than sharing it.

This is a prerequisite for isolating kthreads in nullfs: when
init_task's fs is later pointed at nullfs, PID 1 must not share it
or init_userspace_fs() would modify init_task's fs as well, defeating
the isolation.

At this stage PID 1 still gets rootfs (a private copy rather than a
shared reference), so there is no functional change.

Link: https://patch.msgid.link/20260601-work-kthread-nullfs-v4-19-77ee053060e0@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Change userspace_init_fs from a declared-but-unused extern struct to
a dynamically initialized pointer. Add init_userspace_fs() which is
called early in kernel_init() (PID 1) to record PID 1's fs_struct
as the canonical userspace filesystem state.

Wire up __override_init_fs() and __revert_init_fs() to actually swap
current->fs to/from userspace_init_fs. Previously these were no-ops
that stored current->fs back to itself.

Fix nullfs_userspace_init() to compare against userspace_init_fs
instead of &init_fs. When PID 1 unshares its filesystem state, revert
userspace_init_fs to init_fs's root (nullfs) so that stale filesystem
state is not silently inherited by kworkers and usermodehelpers.

At this stage PID 1's fs still points to rootfs (set by
init_mount_tree), so userspace_init_fs points to rootfs and
scoped_with_init_fs() is functionally equivalent to its previous no-op
behavior.

Link: https://patch.msgid.link/20260601-work-kthread-nullfs-v4-5-77ee053060e0@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Move xbc_snprint_cmdline() from init/main.c to lib/bootconfig.c so the
function (and its xbc_namebuf scratch buffer) becomes part of the shared
parser library. tools/bootconfig already compiles lib/bootconfig.c
directly, which lets a follow-up patch reuse the same renderer in the
userspace tool to convert a bootconfig file into a flat cmdline string
at build time.

No functional change.

Link: https://lore.kernel.org/all/20260508-bootconfig_using_tools-v1-1-1132219aa773@debian.org/

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>