commit 37beb42560165869838e7d91724f3e629db64129 upstream.

kstack_offset was previously maintained per-cpu, but this caused a
couple of issues. So let's instead make it per-task.

Issue 1: add_random_kstack_offset() and choose_random_kstack_offset()
expected and required to be called with interrupts and preemption
disabled so that it could manipulate per-cpu state. But arm64, loongarch
and risc-v are calling them with interrupts and preemption enabled. I
don't _think_ this causes any functional issues, but it's certainly
unexpected and could lead to manipulating the wrong cpu's state, which
could cause a minor performance degradation due to bouncing the cache
lines. By maintaining the state per-task those functions can safely be
called in preemptible context.

Issue 2: add_random_kstack_offset() is called before executing the
syscall and expands the stack using a previously chosen random offset.
choose_random_kstack_offset() is called after executing the syscall and
chooses and stores a new random offset for the next syscall. With
per-cpu storage for this offset, an attacker could force cpu migration
during the execution of the syscall and prevent the offset from being
updated for the original cpu such that it is predictable for the next
syscall on that cpu. By maintaining the state per-task, this problem
goes away because the per-task random offset is updated after the
syscall regardless of which cpu it is executing on.

Fixes: 39218ff4c625 ("stack: Optionally randomize kernel stack offset each syscall")
Closes: https://lore.kernel.org/all/dd8c37bc-795f-4c7a-9086-69e584d8ab24@arm.com/
Cc: stable@vger.kernel.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://patch.msgid.link/20260303150840.3789438-2-ryan.roberts@arm.com
Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull printk updates from Petr Mladek:

 - Add KUnit test for the printk ring buffer

 - Fix the check of the maximal record size which is allowed to be
   stored into the printk ring buffer. It prevents corruptions of the
   ring buffer.

   Note that printk() is on the safe side. The messages are limited by
   1kB buffer and are always small enough for the minimal log buffer
   size 4kB, see CONFIG_LOG_BUF_SHIFT definition.

* tag 'printk-for-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: ringbuffer: Fix data block max size check
  printk: kunit: support offstack cpumask
  printk: kunit: Fix __counted_by() in struct prbtest_rbdata
  printk: ringbuffer: Explain why the KUnit test ignores failed writes
  printk: ringbuffer: Add KUnit test

Pull non-MM updates from Andrew Morton:

 - "ida: Remove the ida_simple_xxx() API" from Christophe Jaillet
   completes the removal of this legacy IDR API

 - "panic: introduce panic status function family" from Jinchao Wang
   provides a number of cleanups to the panic code and its various
   helpers, which were rather ad-hoc and scattered all over the place

 - "tools/delaytop: implement real-time keyboard interaction support"
   from Fan Yu adds a few nice user-facing usability changes to the
   delaytop monitoring tool

 - "efi: Fix EFI boot with kexec handover (KHO)" from Evangelos
   Petrongonas fixes a panic which was happening with the combination of
   EFI and KHO

 - "Squashfs: performance improvement and a sanity check" from Phillip
   Lougher teaches squashfs's lseek() about SEEK_DATA/SEEK_HOLE. A mere
   150x speedup was measured for a well-chosen microbenchmark

 - plus another 50-odd singleton patches all over the place

* tag 'mm-nonmm-stable-2025-10-02-15-29' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (75 commits)
  Squashfs: reject negative file sizes in squashfs_read_inode()
  kallsyms: use kmalloc_array() instead of kmalloc()
  MAINTAINERS: update Sibi Sankar's email address
  Squashfs: add SEEK_DATA/SEEK_HOLE support
  Squashfs: add additional inode sanity checking
  lib/genalloc: fix device leak in of_gen_pool_get()
  panic: remove CONFIG_PANIC_ON_OOPS_VALUE
  ocfs2: fix double free in user_cluster_connect()
  checkpatch: suppress strscpy warnings for userspace tools
  cramfs: fix incorrect physical page address calculation
  kernel: prevent prctl(PR_SET_PDEATHSIG) from racing with parent process exit
  Squashfs: fix uninit-value in squashfs_get_parent
  kho: only fill kimage if KHO is finalized
  ocfs2: avoid extra calls to strlen() after ocfs2_sprintf_system_inode_name()
  kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths
  sched/task.h: fix the wrong comment on task_lock() nesting with tasklist_lock
  coccinelle: platform_no_drv_owner: handle also built-in drivers
  coccinelle: of_table: handle SPI device ID tables
  lib/decompress: use designated initializers for struct compress_format
  efi: support booting with kexec handover (KHO)
  ...

Pull Kbuild updates from Nathan Chancellor:

 - Extend modules.builtin.modinfo to include module aliases from
   MODULE_DEVICE_TABLE for builtin modules so that userspace tools (such
   as kmod) can verify that a particular module alias will be handled by
   a builtin module

 - Bump the minimum version of LLVM for building the kernel to 15.0.0

 - Upgrade several userspace API checks in headers_check.pl to errors

 - Unify and consolidate CONFIG_WERROR / W=e handling

 - Turn assembler and linker warnings into errors with CONFIG_WERROR /
   W=e

 - Respect CONFIG_WERROR / W=e when building userspace programs
   (userprogs)

 - Enable -Werror unconditionally when building host programs
   (hostprogs)

 - Support copy_file_range() and data segment alignment in gen_init_cpio
   to improve performance on filesystems that support reflinks such as
   btrfs and XFS

 - Miscellaneous small changes to scripts and configuration files

* tag 'kbuild-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux: (47 commits)
  modpost: Initialize builtin_modname to stop SIGSEGVs
  Documentation: kbuild: note CONFIG_DEBUG_EFI in reproducible builds
  kbuild: vmlinux.unstripped should always depend on .vmlinux.export.o
  modpost: Create modalias for builtin modules
  modpost: Add modname to mod_device_table alias
  scsi: Always define blogic_pci_tbl structure
  kbuild: extract modules.builtin.modinfo from vmlinux.unstripped
  kbuild: keep .modinfo section in vmlinux.unstripped
  kbuild: always create intermediate vmlinux.unstripped
  s390: vmlinux.lds.S: Reorder sections
  KMSAN: Remove tautological checks
  objtool: Drop noinstr hack for KCSAN_WEAK_MEMORY
  lib/Kconfig.debug: Drop CLANG_VERSION check from DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
  riscv: Remove ld.lld version checks from many TOOLCHAIN_HAS configs
  riscv: Unconditionally use linker relaxation
  riscv: Remove version check for LTO_CLANG selects
  powerpc: Drop unnecessary initializations in __copy_inst_from_kernel_nofault()
  mips: Unconditionally select ARCH_HAS_CURRENT_STACK_POINTER
  arm64: Remove tautological LLVM Kconfig conditions
  ARM: Clean up definition of ARM_HAS_GROUP_RELOCS
  ...

Pull VDSO updates from Thomas Gleixner:

 - Further consolidation of the VDSO infrastructure and the common data
   store

 - Simplification of the related Kconfig logic

 - Improve the VDSO selftest suite

* tag 'timers-vdso-2025-09-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  selftests: vDSO: Drop vdso_test_clock_getres
  selftests: vDSO: vdso_test_abi: Add tests for clock_gettime64()
  selftests: vDSO: vdso_test_abi: Test CPUTIME clocks
  selftests: vDSO: vdso_test_abi: Use explicit indices for name array
  selftests: vDSO: vdso_test_abi: Drop clock availability tests
  selftests: vDSO: vdso_test_abi: Use ksft_finished()
  selftests: vDSO: vdso_test_abi: Correctly skip whole test with missing vDSO
  selftests: vDSO: Fix -Wunitialized in powerpc VDSO_CALL() wrapper
  vdso: Add struct __kernel_old_timeval forward declaration to gettime.h
  vdso: Gate VDSO_GETRANDOM behind HAVE_GENERIC_VDSO
  vdso: Drop Kconfig GENERIC_VDSO_TIME_NS
  vdso: Drop Kconfig GENERIC_VDSO_DATA_STORE
  vdso: Drop kconfig GENERIC_COMPAT_VDSO
  vdso: Drop kconfig GENERIC_VDSO_32
  riscv: vdso: Untangle Kconfig logic
  time: Build generic update_vsyscall() only with generic time vDSO
  vdso/gettimeofday: Remove !CONFIG_TIME_NS stubs
  vdso: Move ENABLE_COMPAT_VDSO from core to arm64
  ARM: VDSO: Remove cntvct_ok global variable
  vdso/datastore: Gate time data behind CONFIG_GENERIC_GETTIMEOFDAY

Pull cgroup updates from Tejun Heo:

 - Extensive cpuset code cleanup and refactoring work with no functional
   changes: CPU mask computation logic refactoring, introducing new
   helpers, removing redundant code paths, and improving error handling
   for better maintainability.

 - A few bug fixes to cpuset including fixes for partition creation
   failures when isolcpus is in use, missing error returns, and null
   pointer access prevention in free_tmpmasks().

 - Core cgroup changes include replacing the global percpu_rwsem with
   per-threadgroup rwsem when writing to cgroup.procs for better
   scalability, workqueue conversions to use WQ_PERCPU and
   system_percpu_wq to prepare for workqueue default switching from
   percpu to unbound, and removal of unused code including the
   post_attach callback.

 - New cgroup.stat.local time accounting feature that tracks frozen time
   duration.

 - Misc changes including selftests updates (new freezer time tests and
   backward compatibility fixes), documentation sync, string function
   safety improvements, and 64-bit division fixes.

* tag 'cgroup-for-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (39 commits)
  cpuset: remove is_prs_invalid helper
  cpuset: remove impossible warning in update_parent_effective_cpumask
  cpuset: remove redundant special case for null input in node mask update
  cpuset: fix missing error return in update_cpumask
  cpuset: Use new excpus for nocpu error check when enabling root partition
  cpuset: fix failure to enable isolated partition when containing isolcpus
  Documentation: cgroup-v2: Sync manual toctree
  cpuset: use partition_cpus_change for setting exclusive cpus
  cpuset: use parse_cpulist for setting cpus.exclusive
  cpuset: introduce partition_cpus_change
  cpuset: refactor cpus_allowed_validate_change
  cpuset: refactor out validate_partition
  cpuset: introduce cpus_excl_conflict and mems_excl_conflict helpers
  cpuset: refactor CPU mask buffer parsing logic
  cpuset: Refactor exclusive CPU mask computation logic
  cpuset: change return type of is_partition_[in]valid to bool
  cpuset: remove unused assignment to trialcs->partition_root_state
  cpuset: move the root cpuset write check earlier
  cgroup/cpuset: Remove redundant rcu_read_lock/unlock() in spin_lock
  cgroup: Remove redundant rcu_read_lock/unlock() in spin_lock
  ...

Pull s390 updates from Alexander Gordeev:

 - Refactor SCLP memory hotplug code

 - Introduce common boot_panic() decompressor helper macro and use it to
   get rid of nearly few identical implementations

 - Take into account additional key generation flags and forward it to
   the ep11 implementation. With that allow users to modify the key
   generation process, e.g. provide valid combinations of XCP_BLOB_*
   flags

 - Replace kmalloc() + copy_from_user() with memdup_user_nul() in s390
   debug facility and HMC driver

 - Add DAX support for DCSS memory block devices

 - Make the compiler statement attribute "assume" available with a new
   __assume macro

 - Rework ffs() and fls() family bitops functions, including source code
   improvements and generated code optimizations. Use the newly
   introduced __assume macro for that

 - Enable additional network features in default configurations

 - Use __GFP_ACCOUNT flag for user page table allocations to add missing
   kmemcg accounting

 - Add WQ_PERCPU flag to explicitly request the use of the per-CPU
   workqueue for 3590 tape driver

 - Switch power reading to the per-CPU and the Hiperdispatch to the
   default workqueue

 - Add memory allocation profiling hooks to allow better profiling data
   and the /proc/allocinfo output similar to other architectures

* tag 's390-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (21 commits)
  s390/mm: Add memory allocation profiling hooks
  s390: Replace use of system_wq with system_dfl_wq
  s390/diag324: Replace use of system_wq with system_percpu_wq
  s390/tape: Add WQ_PERCPU to alloc_workqueue users
  s390/bitops: Switch to generic ffs() if supported by compiler
  s390/bitops: Switch to generic fls(), fls64(), etc.
  s390/mm: Use __GFP_ACCOUNT for user page table allocations
  s390/configs: Enable additional network features
  s390/bitops: Cleanup __flogr()
  s390/bitops: Use __assume() for __flogr() inline assembly return value
  compiler_types: Add __assume macro
  s390/bitops: Limit return value range of __flogr()
  s390/dcssblk: Add DAX support
  s390/hmcdrv: Replace kmalloc() + copy_from_user() with memdup_user_nul()
  s390/debug: Replace kmalloc() + copy_from_user() with memdup_user_nul()
  s390/pkey: Forward keygenflags to ep11_unwrapkey
  s390/boot: Add common boot_panic() code
  s390/bitops: Optimize inlining
  s390/bitops: Slightly optimize ffs() and fls64()
  s390/sclp: Move memory hotplug code for better modularity
  ...

Pull hardening updates from Kees Cook:
 "One notable addition is the creation of the 'transitional' keyword for
  kconfig so CONFIG renaming can go more smoothly.

  This has been a long-standing deficiency, and with the renaming of
  CONFIG_CFI_CLANG to CONFIG_CFI (since GCC will soon have KCFI
  support), this came up again.

  The breadth of the diffstat is mainly this renaming.

   - Clean up usage of TRAILING_OVERLAP() (Gustavo A. R. Silva)

   - lkdtm: fortify: Fix potential NULL dereference on kmalloc failure
     (Junjie Cao)

   - Add str_assert_deassert() helper (Lad Prabhakar)

   - gcc-plugins: Remove TODO_verify_il for GCC >= 16

   - kconfig: Fix BrokenPipeError warnings in selftests

   - kconfig: Add transitional symbol attribute for migration support

   - kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI"

* tag 'hardening-v6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  lib/string_choices: Add str_assert_deassert() helper
  kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI
  kconfig: Add transitional symbol attribute for migration support
  kconfig: Fix BrokenPipeError warnings in selftests
  gcc-plugins: Remove TODO_verify_il for GCC >= 16
  stddef: Introduce __TRAILING_OVERLAP()
  stddef: Remove token-pasting in TRAILING_OVERLAP()
  lkdtm: fortify: Fix potential NULL dereference on kmalloc failure

Pull namespace updates from Christian Brauner:
 "This contains a larger set of changes around the generic namespace
  infrastructure of the kernel.

  Each specific namespace type (net, cgroup, mnt, ...) embedds a struct
  ns_common which carries the reference count of the namespace and so
  on.

  We open-coded and cargo-culted so many quirks for each namespace type
  that it just wasn't scalable anymore. So given there's a bunch of new
  changes coming in that area I've started cleaning all of this up.

  The core change is to make it possible to correctly initialize every
  namespace uniformly and derive the correct initialization settings
  from the type of the namespace such as namespace operations, namespace
  type and so on. This leaves the new ns_common_init() function with a
  single parameter which is the specific namespace type which derives
  the correct parameters statically. This also means the compiler will
  yell as soon as someone does something remotely fishy.

  The ns_common_init() addition also allows us to remove ns_alloc_inum()
  and drops any special-casing of the initial network namespace in the
  network namespace initialization code that Linus complained about.

  Another part is reworking the reference counting. The reference
  counting was open-coded and copy-pasted for each namespace type even
  though they all followed the same rules. This also removes all open
  accesses to the reference count and makes it private and only uses a
  very small set of dedicated helpers to manipulate them just like we do
  for e.g., files.

  In addition this generalizes the mount namespace iteration
  infrastructure introduced a few cycles ago. As reminder, the vfs makes
  it possible to iterate sequentially and bidirectionally through all
  mount namespaces on the system or all mount namespaces that the caller
  holds privilege over. This allow userspace to iterate over all mounts
  in all mount namespaces using the listmount() and statmount() system
  call.

  Each mount namespace has a unique identifier for the lifetime of the
  systems that is exposed to userspace. The network namespace also has a
  unique identifier working exactly the same way. This extends the
  concept to all other namespace types.

  The new nstree type makes it possible to lookup namespaces purely by
  their identifier and to walk the namespace list sequentially and
  bidirectionally for all namespace types, allowing userspace to iterate
  through all namespaces. Looking up namespaces in the namespace tree
  works completely locklessly.

  This also means we can move the mount namespace onto the generic
  infrastructure and remove a bunch of code and members from struct
  mnt_namespace itself.

  There's a bunch of stuff coming on top of this in the future but for
  now this uses the generic namespace tree to extend a concept
  introduced first for pidfs a few cycles ago. For a while now we have
  supported pidfs file handles for pidfds. This has proven to be very
  useful.

  This extends the concept to cover namespaces as well. It is possible
  to encode and decode namespace file handles using the common
  name_to_handle_at() and open_by_handle_at() apis.

  As with pidfs file handles, namespace file handles are exhaustive,
  meaning it is not required to actually hold a reference to nsfs in
  able to decode aka open_by_handle_at() a namespace file handle.
  Instead the FD_NSFS_ROOT constant can be passed which will let the
  kernel grab a reference to the root of nsfs internally and thus decode
  the file handle.

  Namespaces file descriptors can already be derived from pidfds which
  means they aren't subject to overmount protection bugs. IOW, it's
  irrelevant if the caller would not have access to an appropriate
  /proc/<pid>/ns/ directory as they could always just derive the
  namespace based on a pidfd already.

  It has the same advantage as pidfds. It's possible to reliably and for
  the lifetime of the system refer to a namespace without pinning any
  resources and to compare them trivially.

  Permission checking is kept simple. If the caller is located in the
  namespace the file handle refers to they are able to open it otherwise
  they must hold privilege over the owning namespace of the relevant
  namespace.

  The namespace file handle layout is exposed as uapi and has a stable
  and extensible format. For now it simply contains the namespace
  identifier, the namespace type, and the inode number. The stable
  format means that userspace may construct its own namespace file
  handles without going through name_to_handle_at() as they are already
  allowed for pidfs and cgroup file handles"

* tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (65 commits)
  ns: drop assert
  ns: move ns type into struct ns_common
  nstree: make struct ns_tree private
  ns: add ns_debug()
  ns: simplify ns_common_init() further
  cgroup: add missing ns_common include
  ns: use inode initializer for initial namespaces
  selftests/namespaces: verify initial namespace inode numbers
  ns: rename to __ns_ref
  nsfs: port to ns_ref_*() helpers
  net: port to ns_ref_*() helpers
  uts: port to ns_ref_*() helpers
  ipv4: use check_net()
  net: use check_net()
  net-sysfs: use check_net()
  user: port to ns_ref_*() helpers
  time: port to ns_ref_*() helpers
  pid: port to ns_ref_*() helpers
  ipc: port to ns_ref_*() helpers
  cgroup: port to ns_ref_*() helpers
  ...