linux.git/kernel/liveupdate/luo_session.c, branch v7.1-rc2

liveupdate: fix return value on session allocation failure

2026-04-27T12:54:23+00:00

When session allocation fails during deserialization, the global 'err'
variable was not updated before returning.  This caused subsequent calls
to luo_session_deserialize() to incorrectly report success.

Ensure 'err' is set to the error code from PTR_ERR(session).  This ensures
that an error is correctly returned to userspace when it attempts to open
/dev/liveupdate in the new kernel if deserialization failed.

Link: https://lore.kernel.org/20260415193738.515491-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-04-19T15:01:17+00:00

Pull more MM updates from Andrew Morton:

 - "Eliminate Dying Memory Cgroup" (Qi Zheng and Muchun Song)

   Address the longstanding "dying memcg problem". A situation wherein a
   no-longer-used memory control group will hang around for an extended
   period pointlessly consuming memory

 - "fix unexpected type conversions and potential overflows" (Qi Zheng)

   Fix a couple of potential 32-bit/64-bit issues which were identified
   during review of the "Eliminate Dying Memory Cgroup" series

 - "kho: history: track previous kernel version and kexec boot count"
   (Breno Leitao)

   Use Kexec Handover (KHO) to pass the previous kernel's version string
   and the number of kexec reboots since the last cold boot to the next
   kernel, and print it at boot time

 - "liveupdate: prevent double preservation" (Pasha Tatashin)

   Teach LUO to avoid managing the same file across different active
   sessions

 - "liveupdate: Fix module unloading and unregister API" (Pasha
   Tatashin)

   Address an issue with how LUO handles module reference counting and
   unregistration during module unloading

 - "zswap pool per-CPU acomp_ctx simplifications" (Kanchana Sridhar)

   Simplify and clean up the zswap crypto compression handling and
   improve the lifecycle management of zswap pool's per-CPU acomp_ctx
   resources

 - "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race"
   (SeongJae Park)

   Address unlikely but possible leaks and deadlocks in damon_call() and
   damon_walk()

 - "mm/damon/core: validate damos_quota_goal->nid" (SeongJae Park)

   Fix a couple of root-only wild pointer dereferences

 - "Docs/admin-guide/mm/damon: warn commit_inputs vs other params race"
   (SeongJae Park)

   Update the DAMON documentation to warn operators about potential
   races which can occur if the commit_inputs parameter is altered at
   the wrong time

 - "Minor hmm_test fixes and cleanups" (Alistair Popple)

   Bugfixes and a cleanup for the HMM kernel selftests

 - "Modify memfd_luo code" (Chenghao Duan)

   Cleanups, simplifications and speedups to the memfd_lou code

 - "mm, kvm: allow uffd support in guest_memfd" (Mike Rapoport)

   Support for userfaultfd in guest_memfd

 - "selftests/mm: skip several tests when thp is not available" (Chunyu
   Hu)

   Fix several issues in the selftests code which were causing breakage
   when the tests were run on CONFIG_THP=n kernels

 - "mm/mprotect: micro-optimization work" (Pedro Falcato)

   A couple of nice speedups for mprotect()

 - "MAINTAINERS: update KHO and LIVE UPDATE entries" (Pratyush Yadav)

   Document upcoming changes in the maintenance of KHO, LUO, memfd_luo,
   kexec, crash, kdump and probably other kexec-based things - they are
   being moved out of mm.git and into a new git tree

* tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (121 commits)
  MAINTAINERS: add page cache reviewer
  mm/vmscan: avoid false-positive -Wuninitialized warning
  MAINTAINERS: update Dave's kdump reviewer email address
  MAINTAINERS: drop include/linux/liveupdate from LIVE UPDATE
  MAINTAINERS: drop include/linux/kho/abi/ from KHO
  MAINTAINERS: update KHO and LIVE UPDATE maintainers
  MAINTAINERS: update kexec/kdump maintainers entries
  mm/migrate_device: remove dead migration entry check in migrate_vma_collect_huge_pmd()
  selftests: mm: skip charge_reserved_hugetlb without killall
  userfaultfd: allow registration of ranges below mmap_min_addr
  mm/vmstat: fix vmstat_shepherd double-scheduling vmstat_update
  mm/hugetlb: fix early boot crash on parameters without '=' separator
  zram: reject unrecognized type= values in recompress_store()
  docs: proc: document ProtectionKey in smaps
  mm/mprotect: special-case small folios when applying permissions
  mm/mprotect: move softleaf code out of the main function
  mm: remove '!root_reclaim' checking in should_abort_scan()
  mm/sparse: fix comment for section map alignment
  mm/page_io: use sio->len for PSWPIN accounting in sio_read_complete()
  selftests/mm: transhuge_stress: skip the test when thp not available
  ...

liveupdate: remove luo_session_quiesce()

2026-04-18T07:10:50+00:00

Now that FLB module references are handled dynamically during active
sessions, we can safely remove the luo_session_quiesce() and
luo_session_resume() mechanism.

Link: https://lore.kernel.org/20260327033335.696621-7-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

liveupdate: safely print untrusted strings

2026-04-18T07:10:49+00:00

Patch series "liveupdate: Fix module unloading and unregister API", v3.

This patch series addresses an issue with how LUO handles module reference
counting and unregistration during a module unload (e.g., via rmmod).

Currently, modules that register live update file handlers are pinned for
the entire duration they are registered.  This prevents the modules from
being unloaded gracefully, even when no live update session is in
progress.

Furthermore, if a module is forcefully unloaded, the unregistration
functions return an error (e.g.  -EBUSY) if a session is active, which is
ignored by the kernel's module unload path, leaving dangling pointers in
the LUO global lists.

To resolve these issues, this series introduces the following changes:
1. Adds a global read-write semaphore (luo_register_rwlock) to protect
   the registration lists for both file handlers and FLBs.
2. Reduces the scope of module reference counting for file handlers and
   FLBs. Instead of pinning modules indefinitely upon registration,
   references are now taken only when they are actively used in a live
   update session (e.g., during preservation, retrieval, or
   deserialization).
3. Removes the global luo_session_quiesce() mechanism since module
   unload behavior now handles active sessions implicitly.
4. Introduces auto-unregistration of FLBs during file handler
   unregistration to prevent leaving dangling resources.
5. Changes the unregistration functions to return void instead of
   an error code.
6. Fixes a data race in luo_flb_get_private() by introducing a spinlock
   for thread-safe lazy initialization.
7. Strengthens security by using %.*s when printing untrusted deserialized
   compatible strings and session names to prevent out-of-bounds reads.


This patch (of 10):

Deserialized strings from KHO data (such as file handler compatible
strings and session names) are provided by the previous kernel and might
not be null-terminated if the data is corrupted or maliciously crafted.

When printing these strings in error messages, use the %.*s format
specifier with the maximum buffer size to prevent out-of-bounds reads into
adjacent kernel memory.

Link: https://lore.kernel.org/20260327033335.696621-1-pasha.tatashin@soleen.com
Link: https://lore.kernel.org/20260327033335.696621-2-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

liveupdate: propagate file deserialization failures

2026-04-06T18:13:42+00:00

luo_session_deserialize() ignored the return value from
luo_file_deserialize().  As a result, a session could be left partially
restored even though the /dev/liveupdate open path treats deserialization
failures as fatal.

Propagate the error so a failed file deserialization aborts session
deserialization instead of silently continuing.

Link: https://lkml.kernel.org/r/20260325044608.8407-1-leotimmins1974@gmail.com
Link: https://lkml.kernel.org/r/20260325044608.8407-2-leotimmins1974@gmail.com
Fixes: 16cec0d26521 ("liveupdate: luo_session: add ioctls for file preservation")
Signed-off-by: Leo Timmins 
Reviewed-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav 
Cc: Mike Rapoport 
Cc: 
Signed-off-by: Andrew Morton

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using

    git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook

liveupdate: luo_session: add ioctls for file preservation

2025-11-27T22:24:39+00:00

Introducing the userspace interface and internal logic required to manage
the lifecycle of file descriptors within a session.  Previously, a session
was merely a container; this change makes it a functional management unit.

The following capabilities are added:

A new set of ioctl commands are added, which operate on the file
descriptor returned by CREATE_SESSION. This allows userspace to:
- LIVEUPDATE_SESSION_PRESERVE_FD: Add a file descriptor to a session
  to be preserved across the live update.
- LIVEUPDATE_SESSION_RETRIEVE_FD: Retrieve a preserved file in the
  new kernel using its unique token.
- LIVEUPDATE_SESSION_FINISH: finish session

The session's .release handler is enhanced to be state-aware.  When a
session's file descriptor is closed, it correctly unpreserves the session
based on its current state before freeing all associated file resources.

Link: https://lkml.kernel.org/r/20251125165850.3389713-8-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav 
Reviewed-by: Mike Rapoport (Microsoft) 
Tested-by: David Matlack 
Cc: Aleksander Lobakin 
Cc: Alexander Graf 
Cc: Alice Ryhl 
Cc: Andriy Shevchenko 
Cc: anish kumar 
Cc: Anna Schumaker 
Cc: Bartosz Golaszewski 
Cc: Bjorn Helgaas 
Cc: Borislav Betkov 
Cc: Chanwoo Choi 
Cc: Chen Ridong 
Cc: Chris Li 
Cc: Christian Brauner 
Cc: Daniel Wagner 
Cc: Danilo Krummrich 
Cc: Dan Williams 
Cc: David Hildenbrand 
Cc: David Jeffery 
Cc: David Rientjes 
Cc: Greg Kroah-Hartman 
Cc: Guixin Liu 
Cc: "H. Peter Anvin" 
Cc: Hugh Dickins 
Cc: Ilpo Järvinen 
Cc: Ingo Molnar 
Cc: Ira Weiny 
Cc: Jann Horn 
Cc: Jason Gunthorpe 
Cc: Jens Axboe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Lennart Poettering 
Cc: Leon Romanovsky 
Cc: Leon Romanovsky 
Cc: Lukas Wunner 
Cc: Marc Rutland 
Cc: Masahiro Yamada 
Cc: Matthew Maurer 
Cc: Miguel Ojeda 
Cc: Myugnjoo Ham 
Cc: Parav Pandit 
Cc: Pratyush Yadav 
Cc: Randy Dunlap 
Cc: Roman Gushchin 
Cc: Saeed Mahameed 
Cc: Samiullah Khawaja 
Cc: Song Liu 
Cc: Steven Rostedt 
Cc: Stuart Hayes 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Weißschuh 
Cc: Vincent Guittot 
Cc: William Tu 
Cc: Yoann Congal 
Cc: Zhu Yanjun 
Cc: Zijun Hu 
Signed-off-by: Andrew Morton

liveupdate: luo_session: add sessions support

2025-11-27T22:24:38+00:00

Introduce concept of "Live Update Sessions" within the LUO framework.  LUO
sessions provide a mechanism to group and manage `struct file *` instances
(representing file descriptors) that need to be preserved across a
kexec-based live update.

Each session is identified by a unique name and acts as a container for
file objects whose state is critical to a userspace workload, such as a
virtual machine or a high-performance database, aiming to maintain their
functionality across a kernel transition.

This groundwork establishes the framework for preserving file-backed state
across kernel updates, with the actual file data preservation mechanisms
to be implemented in subsequent patches.

[dan.carpenter@linaro.org: fix use after free in luo_session_deserialize()]
  Link: https://lkml.kernel.org/r/c5dd637d7eed3a3be48c5e9fedb881596a3b1f5a.1764163896.git.dan.carpenter@linaro.org
Link: https://lkml.kernel.org/r/20251125165850.3389713-5-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Signed-off-by: Dan Carpenter 
Reviewed-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav 
Tested-by: David Matlack 
Cc: Aleksander Lobakin 
Cc: Alexander Graf 
Cc: Alice Ryhl 
Cc: Andriy Shevchenko 
Cc: anish kumar 
Cc: Anna Schumaker 
Cc: Bartosz Golaszewski 
Cc: Bjorn Helgaas 
Cc: Borislav Betkov 
Cc: Chanwoo Choi 
Cc: Chen Ridong 
Cc: Chris Li 
Cc: Christian Brauner 
Cc: Daniel Wagner 
Cc: Danilo Krummrich 
Cc: Dan Williams 
Cc: David Hildenbrand 
Cc: David Jeffery 
Cc: David Rientjes 
Cc: Greg Kroah-Hartman 
Cc: Guixin Liu 
Cc: "H. Peter Anvin" 
Cc: Hugh Dickins 
Cc: Ilpo Järvinen 
Cc: Ingo Molnar 
Cc: Ira Weiny 
Cc: Jann Horn 
Cc: Jason Gunthorpe 
Cc: Jens Axboe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Lennart Poettering 
Cc: Leon Romanovsky 
Cc: Leon Romanovsky 
Cc: Lukas Wunner 
Cc: Marc Rutland 
Cc: Masahiro Yamada 
Cc: Matthew Maurer 
Cc: Miguel Ojeda 
Cc: Myugnjoo Ham 
Cc: Parav Pandit 
Cc: Pratyush Yadav 
Cc: Randy Dunlap 
Cc: Roman Gushchin 
Cc: Saeed Mahameed 
Cc: Samiullah Khawaja 
Cc: Song Liu 
Cc: Steven Rostedt 
Cc: Stuart Hayes 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Weißschuh 
Cc: Vincent Guittot 
Cc: William Tu 
Cc: Yoann Congal 
Cc: Zhu Yanjun 
Cc: Zijun Hu 
Signed-off-by: Andrew Morton