linux-stable.git/kernel, branch v6.18.38

bpf: use kvfree() for replaced sysctl write buffer

2026-07-04T11:44:19+00:00

commit 4c21b5927d4364bfe7365f2700da5fea0ed0d004 upstream.

proc_sys_call_handler() allocates its temporary sysctl buffer with
kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since
kvzalloc() may fall back to vmalloc() for large allocations, freeing
that buffer with kfree() is wrong and can corrupt memory.

Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc
allocations.

The bug was first flagged by an experimental analysis tool we are
developing for kernel memory-management bugs while analyzing
v6.13-rc1. The tool is still under development and is not yet publicly
available. Manual inspection confirms that the bug is still
present in v7.1-rc5.

Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with
KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the
test tree also included the accompanying fix for the stale ret == 1
check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines
failslab injections to the proc_sys_call_handler() range, uses
stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to
/proc/sys/kernel/domainname from a task in the target cgroup. Under
that setup, fail-nth=1 triggered the fault:

  BUG: unable to handle page fault for address: ffffeb0200024d48
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: Oops: 0000  SMP KASAN NOPTI
  CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4  PREEMPT(lazy)
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
  RIP: 0010:kfree+0x6e/0x510
  ...
  Call Trace:
   
   ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30
   __cgroup_bpf_run_filter_sysctl+0x74d/0xc30
   ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10
   ? srso_return_thunk+0x5/0x5f
   ? __kvmalloc_node_noprof+0x345/0x870
   ? proc_sys_call_handler+0x250/0x480
   ? srso_return_thunk+0x5/0x5f
   proc_sys_call_handler+0x3a2/0x480
   ? __pfx_proc_sys_call_handler+0x10/0x10
   ? srso_return_thunk+0x5/0x5f
   ? selinux_file_permission+0x39f/0x500
   ? srso_return_thunk+0x5/0x5f
   ? lock_is_held_type+0x9e/0x120
   vfs_write+0x98e/0x1000
   ...
   

With this fix applied on top of the same test setup, rerunning the
reproducer with fail-nth=1 yields no corresponding Oops reports.

Fixes: 4508943794ef ("proc: use kvzalloc for our kernel buffer")
Cc: stable@vger.kernel.org

Reviewed-by: Emil Tsalapatis 
Reviewed-by: Jiayuan Chen 
Acked-by: Yonghong Song 
Signed-off-by: Zilin Guan 
Signed-off-by: Dawei Feng 
Link: https://lore.kernel.org/r/20260603105317.944304-3-dawei.feng@seu.edu.cn
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Greg Kroah-Hartman

block: invalidate cached plug timestamp after task switch

2026-07-04T11:44:17+00:00

commit fad156c2af227f42ca796cbb20ddc354a6dd9932 upstream.

blk_time_get_ns() caches ktime_get_ns() in current->plug->cur_ktime
and marks the task with PF_BLOCK_TS. That cache is only valid while the
task keeps running; if the task is switched out, wall-clock time
advances and the cached value must not be reused when the task runs again.

The existing invalidation covers explicit plug flushes through
__blk_flush_plug(), and the schedule() / rtmutex paths through
sched_update_worker(). It does not cover in-kernel preemption paths such
as preempt_schedule(), preempt_schedule_notrace(), and
preempt_schedule_irq(), which enter __schedule(SM_PREEMPT) directly and
return without calling sched_update_worker().

As a result, a task preempted while holding a plug with PF_BLOCK_TS set
can reuse a stale plug->cur_ktime after it is scheduled back in. blk-iocost
then consumes that stale timestamp through ioc_now(), producing stale vnow
values for throttle decisions, and through ioc_rqos_done(), inflating
on-queue time and feeding false missed-QoS samples into vrate
adjustment.

Move the schedule-side invalidation to finish_task_switch(), which runs
for the scheduled-in task after every actual context switch regardless
of which schedule entry point was used. Keep __blk_flush_plug() as the
explicit flush/finish-plug invalidation path, and remove only the
PF_BLOCK_TS handling from sched_update_worker().

Fixes: 06b23f92af87 ("block: update cached timestamp post schedule/preemption")
Cc: stable@vger.kernel.org
Signed-off-by: Usama Arif 
Link: https://patch.msgid.link/20260616141604.328820-3-usama.arif@linux.dev
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

kernel/fork: clear PF_BLOCK_TS in copy_process()

2026-07-04T11:44:17+00:00

commit fd38b75c4b43295b10d69772a46d1c74dbd6fc81 upstream.

PF_BLOCK_TS is only set in blk_time_get_ns() when current->plug is
non-NULL, and blk_finish_plug() clears it via __blk_flush_plug()
before NULLing the plug pointer.  copy_process() breaks the
invariant by inheriting PF_BLOCK_TS from the parent while resetting
the child's plug to NULL.

Clear PF_BLOCK_TS alongside that assignment so callers can rely on
"PF_BLOCK_TS set implies current->plug != NULL" and dereference
current->plug unguarded.

Fixes: 06b23f92af87 ("block: update cached timestamp post schedule/preemption")
Cc: stable@vger.kernel.org
Signed-off-by: Usama Arif 
Link: https://patch.msgid.link/20260616141604.328820-2-usama.arif@linux.dev
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

sched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task()

2026-06-19T11:44:14+00:00

commit 02e545c4297a26dbbc41df81b831e7f605bcd306 upstream.

A WARN fires when systemd's user manager writes "+cpu +memory +pids" to
its own subtree_control while a sched_ext scheduler is loaded:

  WARNING: at kernel/sched/ext.c:3227 scx_cgroup_move_task+0xa8/0xb0
   scx_cgroup_move_task+0xa8/0xb0
   sched_move_task+0x134/0x290
   cpu_cgroup_attach+0x39/0x70
   cgroup_migrate_execute+0x37d/0x450
   cgroup_update_dfl_csses+0x1e3/0x270
   cgroup_subtree_control_write+0x3e7/0x440

scx_cgroup_can_attach() arms cgrp_moving_from only when a task's cpu
cgroup changes. It can still be NULL when scx_cgroup_move_task() runs,
through this sequence:

  Step                               Result
  ---------------------------------  ----------------------------------
  1. cpu enabled on cgroup G         cpu css = A
  2. cpu toggled off then on for G   A killed, B created (same cgroup)
  3. an exiting task keeps A alive   migration skips it, A now stale
  4. +memory migrates G              stale A vs current B pulls cpu in
  5. cpu attach runs for all tasks   hits a live, cpu-unchanged task
  6. scx_cgroup_move_task() on it    cgrp_moving_from NULL -> WARN

The mismatch is that scx_cgroup_can_attach() keys on cgroup identity
while migration drives the move on css identity, so a NULL cgrp_moving_from
here is a legitimate css-only migration, not a missing prep.

The call is already gated on cgrp_moving_from, so just drop the warning.
ops.cgroup_prep_move() and ops.cgroup_move() stay paired.

Fixes: 819513666966 ("sched_ext: Add cgroup support")
Cc: stable@vger.kernel.org # v6.12+
Reported-by: Matt Fleming 
Closes: https://lore.kernel.org/all/20260601124156.2205704-1-mfleming@cloudflare.com/
Signed-off-by: Tejun Heo 
Reviewed-by: Andrea Righi 
[ mfleming: keep the 6.18.y SCX_KF_REST argument in the
  SCX_CALL_OP_TASK() call. ]
Signed-off-by: Matt Fleming 
Signed-off-by: Sasha Levin

locking/rtmutex: Skip remove_waiter() when waiter is not enqueued

2026-06-19T11:44:08+00:00

commit 40a25d59e85b3c8709ac2424d44f65610467871e upstream.

syzbot triggered the following splat in remove_waiter() via
FUTEX_CMP_REQUEUE_PI:

  KASAN: null-ptr-deref in range [0x0000000000000a88-0x0000000000000a8f]
   class_raw_spinlock_constructor
   remove_waiter+0x159/0x1200 kernel/locking/rtmutex.c:1561
   rt_mutex_start_proxy_lock+0x103/0x120
   futex_requeue+0x10e4/0x20d0
   __x64_sys_futex+0x34f/0x4d0

task_blocks_on_rt_mutex() does not arm the waiter upon deadlock detection,
leaving waiter->task nil, where 3bfdc63936dd ("rtmutex: Use waiter::task instead
of current in remove_waiter()") made this fatal.

Furthermore, rt_mutex_start_proxy_lock() should not be calling into remove_waiter()
upon a successfully grabbing the rtmutex. 1a1fb985f2e2 ("futex: Handle early deadlock
return correctly"), moved the remove_waiter() out of __rt_mutex_start_proxy_lock()
(where 'ret' was only ever 0 or < 0) into the wrapper. Tighten this check to
account for try_to_take_rt_mutex().

Fixes: 3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()")
Reported-by: syzbot+78147abe6c524f183ee9@syzkaller.appspotmail.com
Signed-off-by: Davidlohr Bueso 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/all/69f114ac.050a0220.ac8b.0003.GAE@google.com/
Link: https://patch.msgid.link/20260507112913.1019537-1-dave@stgolabs.net
Signed-off-by: Greg Kroah-Hartman

futex/requeue: Prevent NULL pointer dereference in remove_waiter() on self-deadlock

2026-06-19T11:44:07+00:00

commit 74e144274af39935b0f410c0ee4d2b91c3730414 upstream.

When FUTEX_CMP_REQUEUE_PI requeues a non-top waiter that already owns the
target PI futex, task_blocks_on_rt_mutex() returns -EDEADLK before setting
waiter->task.

The subsequent remove_waiter() in rt_mutex_start_proxy_lock() dereferences
the NULL waiter->task, causing a kernel crash.

Add a self-deadlock check for non-top waiters before calling
rt_mutex_start_proxy_lock(), analogous to the top-waiter check in
futex_lock_pi_atomic().

Fixes: 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349 ("rtmutex: Use waiter::task instead of current in remove_waiter()")
Signed-off-by: Ji'an Zhou 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

pidfd: refuse access to tasks that have started exiting harder

2026-06-19T11:44:07+00:00

commit 62c4d31d78294bd61cf3403626b789e854357177 upstream.

The recent ptrace fix closed a hole where someone could rely on task->mm
becoming NULL during do_exit() to bypass dumpability checks. This api
here leans on on the very same check and so inherits the fix.

But there is no good reason to let it succeed at all once the target has
entered do_exit(). PF_EXITING is set by exit_signals() at the very top
of do_exit(), before exit_mm() and exit_files() run. Once we observe it,
the task is committed to dying and exit_files() will release the fdtable
shortly.

Fixes: 8649c322f75c ("pid: Implement pidfd_getfd syscall")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260518-obgleich-petersilie-2d77ccccf9b9@brauner
Signed-off-by: Christian Brauner (Amutable) 
Signed-off-by: Greg Kroah-Hartman

timers/migration: Fix livelock in tmigr_handle_remote_up()

2026-06-19T11:44:07+00:00

commit d486b4934a8e504376b85cdb3766f306d57aff5b upstream.

tmigr_handle_remote_cpu() skips timer_expire_remote() when cpu ==
smp_processor_id(), assuming the local softirq path already handled this
CPU's timers.

This assumption is wrong because jiffies can advance after the handling of
the CPU's global timers in run_timer_base(BASE_GLOBAL) and before
tmigr_handle_remote() evaluates the expiry times.

As a consequence a timer which expires after the CPU local timer wheel
advanced and becomes expired in the remote handling is ignored and the
callback is never invoked and removed from the timer wheel.

What's worse is that fetch_next_timer_interrupt_remote() keeps reporting it
as expired, and the event is re-queued with expires == now on each
iteration.  The goto-again loop spins indefinitely.

Fix this by calling timer_expire_remote() unconditionally. That's minimal
overhead for the common case as __run_timer_base() returns immediately if
there is nothing to expire in the local wheel.

[ tglx: Amend change log and add a comment ]

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Reported-by: Alon Kariv 
Signed-off-by: Amit Matityahu 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260603170139.33628-1-amitmat@amazon.com
Signed-off-by: Greg Kroah-Hartman

tracing/probes: Point the error offset correctly for eprobe argument error

2026-06-19T11:44:03+00:00

commit 85e0f27dd1396307913ffc5745b0c05137e9beac upstream.

Fix to point the error offset correctly for eprobe argument error.
In the cleanup commit 1b8b0cd754cd ("tracing/probes: Move event parameter
fetching code to common parser"), due to incorrect backward compatibility
aimed at conforming to the test specifications, the error location was set
to 0 when a non-existent formal parameter was specified for Eprobe.
However, this should be corrected in both the test and the implementation
to point correct error position.

Link: https://lore.kernel.org/all/177967567399.209006.1451571244515632097.stgit@devnote2/

Fixes: 1b8b0cd754cd ("tracing/probes: Move event parameter fetching code to common parser")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) 
Reviewed-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

dma-debug: fix physical address retrieval in debug_dma_sync_sg_for_device

2026-06-19T11:43:57+00:00

[ Upstream commit 9bfaa86b405381326c971984fd6da184c289713f ]

In debug_dma_sync_sg_for_device(), when iterating over a scatterlist,
the debug entry population mistakenly uses the head of the scatterlist
'sg' to fetch the physical address via sg_phys(), instead of using the
current iterator variable 's'.

This causes dma-debug to track the physical address of the very first
scatterlist entry for all subsequent entries in the list.

Fix this by passing the correct loop iterator 's' to sg_phys()

Fixes: 9d4f645a1fd49ee ("dma-debug: store a phys_addr_t in struct dma_debug_entry")
Signed-off-by: Li RongQing 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260603123708.1665-1-lirongqing@baidu.com
Signed-off-by: Sasha Levin