linux.git/kernel/kcov.c, branch v7.3-rc2

Merge tag 'mm-nonmm-stable-2026-08-22-16-57' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-08-23T15:07:11+00:00

Pull non-MM updates from Andrew Morton:

 - "ocfs2/dlm: bound peer-controlled lengths in the o2dlm" (Bryam
   Vargas)

   Validate and bound all input lengths and count fields in the o2dlm
   migration and recovery receive handlers to prevent memory corruption
   and kernel panics from malformed cluster messages

 - "ocfs2: validate xattr entry bounds" (Cen Zhang)

   Validate OCFS2 extended attribute entry name and value bounds during
   metadata reads to prevent out-of-range memory accesses during
   retrieval or listing operations.

 - "taskstats: fix cgroupstats invalid fd handling and add selftests"
   (Yiyang Chen)

   Return -EBADF when cgroupstats receives an invalid file descriptor to
   prevent caller hangs and misleading success ACKs. Add a kselftest to
   validate valid cgroup v1 queries and verify proper error handling
   across different Netlink flag combinations.

 - "misc lib/raid/ improvements v2" (Christoph Hellwig)

   Improve benchmark-based algorithm selection for the XOR and RAID6
   libraries, add KUnit benchmark tests, and cleanup minor
   implementation details.

 - "ocfs2: cluster: o2hb_region_pin() fixes" (Joseph Qi)

   Fix sleeping-in-atomic, lock order inversion and error-path cleanup
   bugs in o2hb_region_pin() by releasing o2hb_live_lock across sleeping
   configfs_depend_item() calls and using unlocked variants from
   callback context. Ensure failed pin attempts properly decrement user
   counts and unpin partially initialized heartbeat regions to prevent
   memory leaks and unprotected states.

 - "lib/ucs2_string.c: fix out-of-bounds read in ucs2_strnlen()"
   (Vincent Mailhol)

   Fix an off-by-one which could cause an out-of-bounds read.

 - "ocfs2: harden heartbeat teardown races" (Cen Zhang)

   Fix two OCFS2 heartbeat/o2net teardown races found by KASAN.

 - "taskstats: tidy up the cpumask command path" *Bradley Morgan)

   make two small cleanups in kernel/taskstats.c.

 - "ocfs2: validate active orphan slots during inode read" (ZhengYuan
   Huang)

   Validate active ordinary and append-DIO orphan slots read from OCFS2
   dinodes at the metadata boundary to prevent corrupted slot indices
   from causing out-of-bounds array accesses.

 - "ocfs2: bound-check both readdir re-validation scans" (Zhan Xusheng)

   Enforce strict boundary checks on directory entry record lengths and
   offset calculations during OCFS2 directory re-scans to prevent
   out-of-bounds memory reads and directory position corruption.

* tag 'mm-nonmm-stable-2026-08-22-16-57' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (95 commits)
  mailmap: fix bouncing address for Taniya Das
  ocfs2: bound-check dir entries in the inline-data re-validation scan
  ocfs2: bound-check dir entries in the readdir re-validation scan
  squashfs: avoid thundering-herd cache wakeups
  prctl: fix PR_SET_MM_AUXV losing the forced AT_NULL terminator
  mailmap: update email address for Linfeng Sun
  lib/interval_tree: fix allocation warning messages
  checkpatch: add NOKPROBE_SYMBOL to the whitelist of lines that can occur immediately after functions
  Squashfs: check block offset is not negative
  signal: factor out the kernel reserved si_code check
  ocfs2: fix readdir position truncation on 32-bit kernels
  ocfs2: fix cached cluster count after suballocator reclaim
  ocfs2: fix circular locking dependency in ocfs2_init_acl()
  ocfs2: validate DIO orphan slot during inode read
  ocfs2: validate orphan slot during inode read
  selftests/prctl: fix non-anonymous VMA mapping in set-anon-vma-name test
  MAINTAINERS: add IRC and patchwork for LTP
  include/linux/list.h: mark list_add and __list_add as __always_inline
  tools/mm: prevent page_owner_sort from truncating input
  hung_task: update DETECT_HUNG_TASK_BLOCKER Kconfig help
  ...

kcov: fix data corruption and race conditions on PREEMPT_RT

2026-08-05T18:20:13+00:00

syzbot is reporting KCOV state corruption on PREEMPT_RT kernels, for the
temporary storage used for saving/restoring remote KCOV state is currently
allocated as the per-CPU area.

On PREEMPT_RT kernels, softirq handlers run as preemptible task threads
(e.g., ksoftirqd). If a softirq context preempts a task running a remote
KCOV session, it safely saves the task's state into the per-CPU area.
However, if that softirq thread is subsequently preempted by a higher-
priority softirq thread on the same CPU, the second softirq will overwrite
the same per-CPU area, permanently destroying the original task's KCOV
state.

Fix this data corruption by moving the temporary storage from the per-CPU
area to the per-thread area. Since each softirq thread now owns its own
task context, nested softirq preemption no longer causes data overwrites.

Note that while the temporary storage is now on a per-thread basis, the
per-CPU kcov_percpu_data.lock must be retained, for we need to ensure that
kcov_remote_start() and kcov_remote_stop() operate atomically without
racing against asynchronous interrupts that manipulate the current task's
KCOV state.

It is likely that GFP_KERNEL allocation by vmalloc_node() in kcov_init()
has already called panic() before returning NULL, for there will be no
OOM-killable userspace processes when __init function of built-in module
runs. But this patch also fixes crashing the kernel when vmalloc_node()
in kcov_init() returned NULL, for kcov_init() left per-CPU irq_area == NULL
but kcov_remote_start() depends on per-CPU irq_area != NULL, resulting in

  (1) doing vmalloc() in kcov_remote_start() despite !in_task() context

  (2) out-of-array-bounds access if (1) succeeded but
      kcov->remote_size < CONFIG_KCOV_IRQ_AREA_SIZE

  (3) always leak memory allocated by (1), eventually killing all
      OOM-killable userspace processes

problems.

Link: https://lore.kernel.org/43552d09-2ce2-4b19-b0d3-a2d1ab952145@I-love.SAKURA.ne.jp
Reported-by: syzbot+3f51ad7ac3ae57a6fdcc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3f51ad7ac3ae57a6fdcc
Reported-by: syzbot+47cf95ca1f9dcca872c8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=47cf95ca1f9dcca872c8
Reported-by: syzbot+8a173e13208949931dc7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8a173e13208949931dc7
Reported-by: syzbot+90984d3713722683112e@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=90984d3713722683112e
Analyzed-by: AI Mode in Google Search (no mail address)
Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts")
Signed-off-by: Tetsuo Handa 
Reviewed-by: Alexander Potapenko 
Cc: Alan Stern 
Cc: Andrey Konovalov 
Cc: Christoph Hellwig 
Cc: Clark Williams 
Cc: Dmitry Vyukov 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Mark Brown 
Cc: Roman Gushchin 
Cc: Sebastian Andrzej Siewior 
Cc: 
Signed-off-by: Andrew Morton

mm: prefer vma_[start,end]_pgoff() to vma->vm_pgoff in kernel/

2026-08-05T02:19:01+00:00

Be consistent in using vma_start_pgoff() and vma_end_pgoff(), which clearly
indicates which part of the VMA the page offset refers to and aids
greppability.

This is part of a broader series laying the ground to provide a virtual
page offset for MAP_PRIVATE-file backed anon folios.

No functional change intended.

Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-19-2a5aa403d977@kernel.org
Signed-off-by: Lorenzo Stoakes 
Acked-by: Marek Szyprowski  # for kernel/dma
Reviewed-by: Gregory Price 
Acked-by: Pedro Falcato 
Reviewed-by: Vlastimil Babka (SUSE) 
Cc: Ackerley Tng 
Cc: David Hildenbrand (Arm) 
Cc: Kai Huang 
Cc: SJ Park 
Cc: Thomas Zimmermann 
Cc: Liam R. Howlett (Oracle) 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

kcov: use WRITE_ONCE() for selftest mode stores

2026-06-04T21:49:26+00:00

The KCOV selftest enables coverage by setting current->kcov_mode to
KCOV_MODE_TRACE_PC without installing a coverage area.  If an interrupt
records coverage in that window, the access should fault and expose the
bug.

When building for QEMU raspi0 (Raspberry Pi Zero, ARMv6, CONFIG_CPU_V6K=y,
CONFIG_CURRENT_POINTER_IN_TPIDRURO=y) with GCC 13.3.0, the store that
enables the mode is removed.  The generated kcov_init() code only stores
zero after the wait loop:

  mrc	15, 0, r3, cr13, cr0, {3}
  str	r4, [r3, #2028]

where r4 is zero.  There is no store of KCOV_MODE_TRACE_PC before the
loop, so the selftest reports success without exercising coverage.

Use WRITE_ONCE() for the temporary mode stores.  With the same compiler
and config, kcov_init() contains the intended mode store:

  mov	r3, #2
  mrc	15, 0, r2, cr13, cr0, {3}
  str	r3, [r2, #2028]

Now that the KCOV selftest is actually executed, it may expose KCOV
instrumentation issues depending on the kernel config.  That is expected
for a selftest that was intended to catch coverage from interrupt paths.

Link: https://lore.kernel.org/20260526114715.38280-1-kmehltretter@gmail.com
Fixes: 6cd0dd934b03 ("kcov: Add interrupt handling self test")
Assisted-by: Codex:gpt-5
Signed-off-by: Karl Mehltretter 
Reviewed-by: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Dmitry Vyukov 
Cc: Kees Cook 
Cc: Marco Elver 
Cc: Peter Zijlstra 
Cc: 
Signed-off-by: Andrew Morton

kcov: allow simultaneous KCOV_ENABLE/KCOV_REMOTE_ENABLE

2026-05-29T04:24:51+00:00

Allow the same userspace thread to simultaneously collect normal coverage
in syscall context (KCOV_ENABLE) and remote coverage of asynchronous work
created by the thread (KCOV_REMOTE_ENABLE).  With this, remote KCOV
coverage becomes useful for generic fuzzing and not just fuzzing of
specific data injection interfaces.

This requires that the task_struct::kcov_* fields are separated into ones
that are used by the task that generates coverage, and ones that are used
by the task that requested remote coverage.  To split this up:

 - Split task_struct::kcov into kcov and kcov_remote. kcov_task_exit() now
   has to clean up both separately.
 - Only use task_struct::kcov_mode on the task that generates coverage.
 - Only reset task_struct::kcov_handle on the task that requested remote
   coverage.

After this change, fields used by the task that generates coverage are:

 - kcov_mode
 - kcov_size
 - kcov_area
 - kcov
 - kcov_sequence
 - kcov_softirq

Fields used by the task that requested remote coverage are:

 - kcov_remote
 - kcov_handle

[jannh@google.com: remove unused constant KCOV_MODE_REMOTE, per Dmitry]
  Link: https://lore.kernel.org/20260515-kcov-simultaneous-remote-v2-1-56fde1cfa509@google.com
[jannh@google.com: update documentation on remote coverage collection]
  Link: https://lore.kernel.org/20260519-kcov-docs-v1-1-5bb22f4cb20c@google.com
[jannh@google.com: move and reword sentence on simultaneous normal/remote collection
  Link: https://lore.kernel.org/20260520-kcov-docs-v2-1-819f78778763@google.com
Link: https://lore.kernel.org/20260505-kcov-simultaneous-remote-v1-1-a670ba7cefd2@google.com
Signed-off-by: Jann Horn 
Reviewed-by: Dmitry Vyukov 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Marco Elver 
Signed-off-by: Andrew Morton

kcov: refactor common handle ID into kcov_common_handle_id

2026-05-29T04:24:45+00:00

Store common handle IDs in "struct kcov_common_handle_id", which consumes
no space in non-KCOV builds.

This cleanup removes #ifdef boilerplate code from subsystems that
integrate with KCOV (in particular in usbip_common.h and skbuff.h, see the
diffstat).

This should also make it easier to add KCOV remote coverage to more
subsystems in the future.

Link: https://lore.kernel.org/20260430-kcov-refactor-common-handle-v1-1-23a0c7a0ba38@google.com
Signed-off-by: Jann Horn 
Acked-by: Greg Kroah-Hartman 
Reviewed-by: Dmitry Vyukov 
Acked-by: Jakub Kicinski 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Eugenio Pérez 
Cc: Hongren (Zenithal) Zheng 
Cc: Jann Horn 
Cc: Jason Wang 
Cc: "Michael S. Tsirkin" 
Cc: Shuah Khan 
Cc: Valentina Manea 
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

kcov: Use scoped init guard

2026-01-28T19:45:24+00:00

Convert lock initialization to scoped guarded initialization where
lock-guarded members are initialized in the same scope.

This ensures the context analysis treats the context as active during
member initialization. This is required to avoid errors once implicit
context assertion is removed.

Signed-off-by: Marco Elver 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://patch.msgid.link/20260119094029.1344361-4-elver@google.com

kcov: Enable context analysis

2026-01-05T15:43:34+00:00

Enable context analysis for the KCOV subsystem.

Signed-off-by: Marco Elver 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://patch.msgid.link/20251219154418.3592607-30-elver@google.com