Pull scheduler fix from Ingo Molnar:
- Fix wakeups of deferred DL servers to be actually deferred (Gabriele
Monaco)
* tag 'sched-urgent-2026-08-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Use revised wakeup rule only for running dl_server
Commit 14a8570564 ("sched/deadline: Use revised wakeup rule for
dl_server") applies the revised wakeup rule to any server, as a result
servers that are not running (dl_defer_running == 0) and start with a
deadline overflow get enqueued and can boost tasks as if they were
running, invalidating the defer rule and the documented state model.
Apply the revised wakeup rule only for deferrable servers that are
marked as running.
Fixes: 14a8570564 ("sched/deadline: Use revised wakeup rule for dl_server")
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Tested-by: Andrea Righi <arighi@nvidia.com>
Link: https://patch.msgid.link/20260522125833.264145-1-gmonaco@redhat.com
Commit 16a03c71bb ("cpufreq: schedutil: Merge initialization code of
sg_cpu in single loop") merged the per-CPU initialization and the
utilization-hook registration into a single loop in sugov_start().
For a shared cpufreq policy this re-introduces the race originally fixed
by commit ab2f7cf141 ("cpufreq: schedutil: Fix sugov_start() versus
sugov_update_shared() race").
The scheduler's util path reaches the hook under RCU-sched and never takes
policy->rwsem, so the rwsem held across sugov_start() cannot serialize the
two. Once the first CPU's hook is published, sugov_update_shared() may run
and, via sugov_next_freq_shared(), read/write each sibling sugov_cpu
(iowait_boost, util, bw_min, ...) concurrently with the memset() still
initializing them, with no lock common to both sides: the update side holds
sg_policy->update_lock while the init side holds only policy->rwsem, which
the scheduler's util path never takes.
The walk only accesses scalar members, never a pointer like ->sg_policy,
so it does not crash today; it merely uses stale (or zero on first start)
values that skew the frequency selection and tracepoints. It is still a
genuine data race, and a latent crash once any pointer member is
dereferenced there.
Restore the two-phase approach: initialize all per-CPU structures first,
and only then publish the per-CPU utilization update hooks.
Fixes: 16a03c71bb ("cpufreq: schedutil: Merge initialization code of sg_cpu in single loop")
Cc: stable@vger.kernel.org
Signed-off-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260716115159.848403-1-zhongqiu.han@oss.qualcomm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Pull sched_ext fixes from Tejun Heo:
- Lifecycle fixes for the new sub-scheduler support: two
use-after-frees and an enable-failure path that left a
half-initialized sub-scheduler linked.
- Two dispatch-path locking bugs: a spurious scheduler abort from a
migration race, and a lockdep splat from stale runqueue-lock
tracking.
- Callback and task-state fixes: stale scheduler-owned state on a task
leaving SCX, a weight callback running after disable, and a bogus
warning on core-scheduling forced idle.
- On nohz_full, finite-slice tasks could miss the tick that expires
their slice. Enable it when such a task is picked, with a selftest.
- Smaller fixes: userspace CPU-mask helpers, ratelimited deprecation
warnings, docs and a sparse annotation.
* tag 'sched_ext-for-7.2-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: Skip ops.set_weight() for disabled tasks
tools/sched_ext: scx - Fix cmask_subset(), cmask_equal() and cmask_weight()
sched_ext: Fix premature ops->priv publication in scx_alloc_and_add_sched()
sched_ext: Record an error on errno-only sub-enable failure
selftests/sched_ext: Verify nohz_full tick behavior
sched_ext: Enable tick for finite slices on nohz_full
sched_ext: Preserve rq tracking across local DSQ dispatch
sched_ext: Documentation: Fix ops table header reference
sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()
sched_ext: Pin parent scx_sched across a child sub-scheduler's lifetime
sched_ext: Annotate ksyncs with __rcu in alloc/free_kick_syncs()
sched_ext: Check remote rq eligibility under task's rq lock
sched_ext: Reset dsq_vtime and slice when a task leaves SCX
sched_ext: Avoid flooding the log with deprecation warnings
When switching a task's sched_class away from sched_ext, we get the
following sequence of events in __sched_setscheduler():
sched_change_begin()
switched_from_scx()
scx_disable_task(p)
ops.disable(p)
__setscheduler_params()
set_load_weight()
reweight_task_scx(p)
ops.set_weight(p)
p->sched_class = next_class;
sched_change_end()
...
Notably, ops.set_weight() is called _after_ ops.disable().
This violates the expected semantics of the callbacks, the expectation
being that ops.disable() can only be followed by ops.exit_task() or
ops.enable().
Skipping the weight adjustment for disabled tasks should be harmless
since the weight will be recalculated in scx_enable_task() if the task
ever rejoins SCX.
Fixes: 637b068282 ("sched: Fold sched_class::switch{ing,ed}_{to,from}() into the change pattern")
Cc: stable@vger.kernel.org # v6.19+
Signed-off-by: Kuba Piecuch <jpiecuch@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
scx_alloc_and_add_sched() publishes @sch through ops->priv before allocating
the cgroup path. If that allocation fails, the unwind path clears ops->priv
and frees @sch immediately. scx_prog_sched() callers can dereference
ops->priv from RCU context the moment it is set, so freeing without a grace
period can use-after-free a concurrent kfunc caller.
Move the publication below the cgroup path allocation so that every failure
path after publication frees @sch through kobject_put(), whose release path
defers the freeing by a grace period.
Fixes: 105dcd005b ("sched_ext: Introduce scx_prog_sched()")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
scx_sub_enable_workfn() has several failure paths that only return an errno
(e.g. -ENOMEM from an allocation) and jump to err_disable without calling
scx_error(). scx_flush_disable_work() runs the disable, and thus ops.exit(),
only when an error has been recorded, so an errno-only failure leaves the
half-initialized sub-scheduler linked.
Record an error at the err_disable sink so every errno-only failure runs the
disable path.
Fixes: ebeca1f930 ("sched_ext: Introduce cgroup sub-sched support")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
set_next_task_scx() updates the tick dependency before __schedule()
updates rq->curr. When switching from a non-EXT task, such as idle, to
an EXT task with a finite slice, sched_update_tick_dependency() checks
the outgoing task and can allow the tick to remain stopped.
The dependency can also be lost without a slice-type transition. After a
finite-slice task leaves the CPU idle, the enqueue path can clear the
dependency against the idle rq->curr. SCX_RQ_CAN_STOP_TICK still records
a finite slice, so another finite task skips the transition block and
can run without the ticks needed to expire its slice.
The reverse mismatch can also happen when the last finite-slice EXT task
is dequeued: sub_nr_running() updates the dependency before rq->curr
changes, so the outgoing task state can keep the dependency set after
the CPU goes idle.
Fix this by unconditionally enabling the scheduler tick whenever a
finite-slice EXT task is selected on a nohz_full CPU. Moreover, when the
last runnable EXT task leaves, ignore the outgoing EXT slice state so
the generic scheduler can correctly re-evaluate and clear the tick
dependency.
Fixes: 22a920209a ("sched_ext: Implement tickless support")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
dispatch_to_local_dsq() can run from scx_bpf_dsq_move_to_local() while
ops.dispatch() has recorded the current rq. Moving a task to a local DSQ
may switch to the source or destination rq before synchronously invoking
ops.dequeue() through the following path:
SCX_CALL_OP(dispatch, rq)
ops.dispatch()
scx_bpf_dsq_move_to_local()
scx_flush_dispatch_buf()
finish_dispatch()
dispatch_to_local_dsq()
scx_dispatch_enqueue()
local_dsq_post_enq()
call_task_dequeue()
SCX_CALL_OP_TASK(dequeue, locked_rq, ...)
The nested callback saves the recorded rq and restores it on return. If
the rq tracking does not follow the lock switch, update_locked_rq() can
trigger the following lockdep assertion while restoring an rq which is
no longer held:
WARNING: kernel/sched/sched.h:1641 at call_task_dequeue+0x160/0x170
Call Trace:
scx_dispatch_enqueue+0x2b0/0x460
dispatch_to_local_dsq+0x138/0x230
scx_flush_dispatch_buf+0x1af/0x220
scx_bpf_dsq_move_to_local___v2+0xe2/0x1c0
bpf__sched_ext_ops_dispatch+0x4b/0xa7
do_pick_task_scx+0x3b6/0x910
__pick_next_task+0x105/0x1f0
__schedule+0x3e7/0x1980
Introduce switch_rq_lock() to update the tracking state together with
each rq lock handoff. Use it in dispatch_to_local_dsq(),
move_remote_task_to_local_dsq() and the in-balance paths of
scx_dsq_move(), ensuring that scx_locked_rq() consistently refers to the
rq whose lock is actually held throughout the lock dance.
Fixes: 7fb39e4eb4 ("sched_ext: Save and restore scx_locked_rq across SCX_CALL_OP")
Cc: stable@vger.kernel.org # 7.1+
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
put_prev_task_scx() warns when a runnable task drops to a lower sched_class
without SCX_OPS_ENQ_LAST, on the assumption that balance_one() would have
kept it running. Core scheduling breaks that: a forced-idle SMT sibling
reschedules through the core_pick fast path in pick_next_task(), which skips
pick_task_scx() and thus balance_one(), so a runnable task can drop to idle
with ENQ_LAST unset.
Gate the warning on sched_cpu_cookie_match(): a cookie mismatch means core
scheduling forced the idle, while a match (or core scheduling off) still
catches a genuine missing-ENQ_LAST drop.
Fixes: 7c65ae81ea ("sched_ext: Don't call put_prev_task_scx() before picking the next task")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
A child sub-scheduler dereferences its parent scx_sched throughout its life,
e.g., in scx_sub_disable() which reparents the child's tasks and calls
parent->ops.sub_detach() after unlinking from the parent. However, the
parent is pinned only through parent->sub_kset, which is dropped during
disable. The parent scx_sched can be RCU-freed while a child is still
disabling.
Take a direct reference on the parent in scx_alloc_and_add_sched(), dropped
in scx_sched_free_rcu_work(), so a parent always outlives its descendants.
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull power management fixes from Rafael Wysocki:
"These fix the schedutil cpufreq governor and drop a bogus warning
from the cpuidle core:
- Remove a misguided warning along with an inaccurate comment
next to it from the cpuidle core (Rafael Wysocki)
- Clear need_freq_update as appropriate in the .adjust_perf()
path of the schedutil cpufreq governor to avoid calling
cpufreq_driver_adjust_perf() unnecessarily on every scheduler
utilization update (Zhongqiu Han)"
* tag 'pm-7.2-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpuidle: Allow exit latency to exceed target residency
cpufreq: schedutil: Fix uncleared need_freq_update on the .adjust_perf() path
Pull block fixes from Jens Axboe:
- blk-cgroup locking rework and fixes:
- fix a use-after-free in __blkcg_rstat_flush()
- defer freeing policy data until after an RCU grace period
- defer the blkcg css_put until the blkg is unlinked from
the queue
- unwind the queue_lock nesting under RCU / blkcg->lock
across the lookup, create, associate and destroy paths
- NVMe fixes via Keith:
- Fix a crash and memory leak during invalid cdev teardown,
and related cdev cleanups (Maurizio, John)
- nvmet fixes: handle TCP_CLOSING in the tcp state_change
handler, reject short AUTH_RECEIVE buffers, handle inline
data with a nonzero offset in rdma, fix an sq refcount leak,
and allocate ana_state with the port (Maurizio, Michael,
Bryam, Wentao, Rosen)
- nvme-fc fix to not cancel requests on an IO target before it
is initialized (Mohamed)
- nvme-apple fix to prevent shared tags across queues on Apple
A11 (Nick)
- Various smaller fixes and cleanups (John)
- MD fixes via Yu Kuai:
- raid1/raid10 fixes for writes_pending and barrier reference
leaks on write and discard failures, plus REQ_NOWAIT handling
fixes (Abd-Alrhman)
- raid5 discard accounting and validation, and a batch of fixes
for stripe batch races (Yu Kuai, Chen)
- Protect raid1 head_position during read balancing (Chen)
- block bio-integrity fixes: correct an error injection static key
decrement, fix GFP flag confusion in bio_integrity_alloc_buf(), and
handle REQ_OP_ZONE_APPEND in __bio_integrity_action() (Christoph)
- Fixes for bio_iov_iter_bounce_write(): revert the iov_iter after a
short copy, and respect the iov_iter nofault flag (Qu)
- Invalidate the cached plug timestamp after a task switch, and clear
PF_BLOCK_TS in copy_process() (Usama)
- Fix the IORING_URING_CMD_REISSUE flags check in blkdev_uring_cmd()
(Yitang)
- Remove a redundant plug in __submit_bio() (Wen)
- Don't warn when reclassifying a busy socket lock in nbd (Deepanshu)
* tag 'block-7.2-20260625' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux: (45 commits)
block: handle REQ_OP_ZONE_APPEND in __bio_integrity_action
block: fix GFP_ flags confusion in bio_integrity_alloc_buf
block, bfq: don't grab queue_lock to initialize bfq
mm/page_io: don't nest queue_lock under rcu in bio_associate_blkg_from_page()
blk-cgroup: don't nest queue_lock under blkcg->lock in blkcg_destroy_blkgs()
blk-cgroup: don't nest queue_lock under rcu in bio_associate_blkg()
blk-cgroup: don't nest queue_lock under rcu in blkg_lookup_create()
blk-cgroup: don't nest queue_lock under rcu in blkcg_print_blkgs()
blk-cgroup: delay freeing policy data after rcu grace period
blk-cgroup: protect iterating blkgs with blkcg->lock in blkcg_print_stat()
md/raid5: avoid R5_Overlap races while breaking stripe batches
md/raid5: use stripe state snapshot in break_stripe_batch_list()
blk-cgroup: defer blkcg css_put until blkg is unlinked from queue
blk-cgroup: fix UAF in __blkcg_rstat_flush()
block, bfq: protect async queue reset with blkcg locks
nbd: don't warn when reclassifying a busy socket lock
block: fix incorrect error injection static key decrement
md/raid5: let stripe batch bm_seq comparison wrap-safe
md/raid1: protect head_position for read balance
md/raid1: free r1_bio when REQ_NOWAIT is set and read would block on retry
...
scx_kick_syncs is a per-CPU __rcu pointer, so per_cpu_ptr() returns struct
scx_kick_syncs __rcu **. alloc_kick_syncs() and free_kick_syncs() stored it
in a plain struct scx_kick_syncs **ksyncs, which sparse flags as an __rcu
address-space mismatch. Annotate ksyncs to match. Its accesses already go
through rcu_*_pointer().
Fixes: 987e00035c ("sched_ext: Rename pnt_seq to kick_sync")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202606122315.pbnDHP0n-lkp@intel.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
task_can_run_on_remote_rq() operates under the assumption that
p->migration_disabled is stable, i.e. if the kernel observed
is_migration_disabled(p) == true, then the BPF scheduler must have also
been able to see this when dispatching the task, and it's the BPF
scheduler's fault that it tried to dispatch a task with migration
disabled to a CPU other than the task's current CPU.
This assumption does not always hold. It's possible that the BPF
scheduler saw is_migration_disabled(p) == false, while the kernel
observes is_migration_disabled(p) == true in dispatch_to_local_dsq()
-> task_can_run_on_remote_rq().
The crucial thing here is that with CONFIG_PREEMPT_RCU, migration is
disabled while a task is executing a BPF program. So, if there's a
situation where the BPF scheduler checks a task while it's not executing
a BPF program, while the kernel checks it while it is executing one,
the BPF scheduler will be killed through no fault of its own.
Consider the following scenario:
1. SCX task @p is executing on CPU A and CPU A gets preempted by a
higher-priority scheduling class. On entry to __schedule(),
p->migration_disabled == 0.
2. In put_prev_task_scx() @p is enqueued on the BPF scheduler's internal
data structures, making it available for other CPUs to dispatch.
3. CPU B enters ops.dispatch(), pops @p from the BPF scheduler's data
structures, checks is_migration_disabled(p) which returns false,
and dispatches @p to CPU B's local DSQ.
4. On CPU A, @p hasn't been switched out yet. Execution reaches
trace_sched_switch() which enters a BPF program, as the BPF scheduler
hooks into the sched_switch tracepoint to detect idle->fair
transitions. On entry into the BPF program, @p disables migration.
5. CPU B enters finish_dispatch() -> dispatch_to_local_dsq() ->
task_can_run_on_remote_rq() which observes
is_migration_disabled(p) == true, triggering scx_error().
This all happens while holding CPU B's rq lock, so it's not
synchronized with @p switching out.
This patch fixes this by moving the call to task_can_run_on_remote_rq()
after @p's rq lock is acquired in dispatch_to_local_dsq(). This way, we
synchronize with @p switching out, since @p holds its rq lock all
the way until it's switched out. Thus, any BPF programs that are called
between put_prev_task_scx() and the end of the context switch are
guaranteed to have finished and cannot influence p->migration_disabled.
Also add a lockdep assertion in task_can_run_on_remote_rq() which
ensures the task rq lock is held if enforce == true.
Signed-off-by: Kuba Piecuch <jpiecuch@google.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When a task leaves the BPF scheduler's control, p->scx.dsq_vtime and
p->scx.slice keep whatever values they last held. The slice value is
core-managed and is refilled on the next enqueue, but dsq_vtime is owned
by the BPF scheduler and is never cleared by the core, so a task that
leaves SCX and later returns carries a stale dsq_vtime across the
round-trip.
The stale values are also visible to other SCX schedulers that inspect
the scx fields of non-SCX tasks.
Fix this by resetting both dsq_vtime and slice in scx_disable_task(),
after ops.disable(), so the BPF scheduler can still observe the task's
final values and non-SCX tasks do not retain stale SCX state.
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The deprecation notices for direct p->scx.slice/dsq_vtime writes and for
ops->cpu_acquire/release() use plain pr_warn(), so they repeat on every
scheduler (re)load and can flood the kernel log.
The slice/dsq_vtime notice is the worst offender: it is emitted from the
BPF verifier's btf_struct_access callback, which is re-evaluated as the
verifier explores program paths, so a single scheduler load can print it
many times -- hundreds of lines on some hosts, dozens within the same
second.
Switch both notices to pr_warn_ratelimited() so each deprecation is still
reported but bursts no longer spam the log, and add the missing newline
to the slice/dsq_vtime message.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull misc core fixes from Ingo Molnar:
- Fix an MM-CID race that can cause an OOB write (Rik van Riel)
- Fix a debugobjects OOM handling race (Thomas Gleixner)
* tag 'core-urgent-2026-06-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
debugobjects: Plug race against a concurrent OOM disable
sched/mmcid: Fix OOB clear_bit when CID is MM_CID_UNSET in fixup path
Pull sched_ext tree reorg from Tejun Heo:
"Pure source reorganization with no functional change:
- the kernel/sched/ext* files move into a new kernel/sched/ext/
subdirectory
- the headers and sources are made self-contained so editor tooling
can parse each file on its own"
* tag 'sched_ext-for-7.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: Move shared helpers from ext.c into internal.h and cid.h
sched_ext: Make kernel/sched/ext/ sources self-contained for clangd
sched_ext: Move sources under kernel/sched/ext/
idle.c and cid.c are included into build_policy.c together with ext.c and
use helpers that ext.c defines. Because the helpers live in ext.c, the two
files can not parse as standalone units and clangd reports errors in them.
Move the helpers to the headers they belong to. The op-dispatch macros and
helpers plus scx_parent() to internal.h, and scx_cpu_arg()/scx_cpu_ret() to
cid.h. No functional change. idle.c and cid.c now parse clean standalone.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
The sources under kernel/sched/ext/ build as a single translation unit:
build_policy.c includes the source files and headers. An LSP/clangd editor
parses each as a standalone unit, sees no types, and reports a flood of
errors.
Give each header its dependencies and include guard, and have each source
include the headers it uses.
ext.c, arena.c and the ext headers now parse clean standalone. idle.c and
cid.c still reference a few macros and helpers defined in ext.c. The next
patch moves those to shared headers.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
The sched_ext sources had grown to ten ext* files directly under
kernel/sched/. Move them into a new kernel/sched/ext/ subdirectory and drop
the now-redundant ext_ prefix. ext.c/h keep their names.
kernel/sched/ext.{c,h} -> kernel/sched/ext/ext.{c,h}
kernel/sched/ext_internal.h -> kernel/sched/ext/internal.h
kernel/sched/ext_types.h -> kernel/sched/ext/types.h
kernel/sched/ext_idle.{c,h} -> kernel/sched/ext/idle.{c,h}
kernel/sched/ext_cid.{c,h} -> kernel/sched/ext/cid.{c,h}
kernel/sched/ext_arena.{c,h} -> kernel/sched/ext/arena.{c,h}
The include paths in build_policy.c and sched.h, the MAINTAINERS glob, and a
few documentation and comment references are updated to match. No code or
symbol changes.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull more s390 updates from Alexander Gordeev:
- consolidate s390 idle time accounting by moving all CPU time tracking
to the architecture backend and eliminate the mix of architecture-
specific and common code accounting
- Add missing EXPORT_SYMBOL_GPL() to kcpustat_field_idle() and
kcpustat_field_iowait() functions
- Finalize ptep_get() conversion by replacing direct page table entry
dereferencing with proper accessors (ptep_get(), pmdp_get(), etc.)
- Explicitly check the buffer length in PKEY_VERIFYPROTK ioctl and
pkey_pckmo implementations and fail if the length is exceeded
* tag 's390-7.2-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
s390/pkey: Check length in pkey_pckmo handler implementation
s390/pkey: Check length in PKEY_VERIFYPROTK ioctl
s390/idle: Add missing EXPORT_SYMBOL_GPL()
s390/mm: Complete ptep_get() conversion
s390/idle: Remove idle time and count sysfs files
s390/idle: Provide arch specific kcpustat_field_idle()/kcpustat_field_iowait()
s390/irq/idle: Use stcke instead of stckf for time stamps
s390/timex: Move union tod_clock type to separate header
In mm_cid_fixup_cpus_to_tasks(), when rq->curr has the target mm and
mm_cid.active is set, the CID is checked with cid_in_transit() before
setting the transition bit. In per-CPU mode a newly forked or exec'd
task can be running with mm_cid.cid == MM_CID_UNSET because CIDs are
assigned lazily on schedule-in. With cid_in_transit() the guard passes
for MM_CID_UNSET (no transit bit), converts it to MM_CID_UNSET |
MM_CID_TRANSIT and stores it back; later mm_cid_schedout() feeds this
to clear_bit() with MM_CID_UNSET as the bit number, triggering an
out-of-bounds write.
Symptoms: this is genuine memory corruption, but a bounded out-of-bounds
write, not an arbitrary one. MM_CID_UNSET is the fixed sentinel BIT(31),
so once the bad value reaches mm_cid_schedout() the cid_from_transit_cid()
strip leaves MM_CID_UNSET, which fails the "cid < max_cids" convergence
test and falls into mm_drop_cid() -> clear_bit(MM_CID_UNSET,
mm_cidmask(mm)). The cid bitmap is embedded in the mm_struct slab object
(after cpu_bitmap and mm_cpus_allowed) and is only num_possible_cpus()
bits wide, so clearing bit 31 is a deterministic OOB bit-clear at a
fixed offset of 2^31 / 8 == 256 MiB past the bitmap base. The address is
not attacker-influenced (fixed sentinel -> fixed offset) and the op only
clears a single bit; what sits 256 MiB further along the direct map is
whatever kernel object happens to live there, so this corrupts one bit of
unpredictable kernel memory -- it is not an arbitrary-address or
arbitrary-value write.
It triggers only in per-CPU CID mode, when a CPU is running an active
task of the target mm whose cid is still MM_CID_UNSET -- the
fork()/execve() window before that task's next schedule-in assigns it a
real CID -- and a per-CPU -> per-task fixup walks over it (the mode
fallback driven by a thread exit, sched_mm_cid_exit(), or by the deferred
max_cids recompute in mm_cid_work_fn()).
In practice syzkaller surfaced it as a KASAN use-after-free reported in
__schedule -> mm_cid_switch_to, where the offending clear_bit() is inlined
via mm_cid_schedout() -> mm_drop_cid().
Guard the transition-bit assignment against MM_CID_UNSET, in addition to
the existing cid_in_transit() check, so the bit is only set on a genuine
task-owned CID. A CPU-owned (MM_CID_ONCPU) CID of a running active task
is handled by the cid_on_cpu(pcp->cid) branch above and never reaches
this path, so excluding MM_CID_UNSET (and the already-transitioning case)
is sufficient.
Fixes: fbd0e71dc3 ("sched/mmcid: Provide CID ownership mode fixup functions")
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Claude:claude-opus-4-8 syzkaller
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260616203818.1516263-1-riel@surriel.com
The need_freq_update flag makes sugov_should_update_freq() return true
regardless of the rate_limit_us throttling, and is cleared in
sugov_update_next_freq(). sugov_update_single_freq() and
sugov_update_shared() go through that helper, so the flag does not
persist there.
However, sugov_update_single_perf(), used by drivers implementing the
.adjust_perf() callback (e.g. intel_pstate or amd-pstate in passive
mode) calls cpufreq_driver_adjust_perf() directly and never goes through
sugov_update_next_freq(), so the need_freq_update flag is not cleared in
that path.
Before commit 75da043d8f ("cpufreq/sched: Set need_freq_update in
ignore_dl_rate_limit()"), this was effectively harmless because
sugov_should_update_freq() still honored the rate limit even when
need_freq_update was set. After that change, the flag forces
sugov_should_update_freq() to always return true, so once set, it
stays effective indefinitely on the .adjust_perf() path.
As a result, cpufreq_driver_adjust_perf() gets called on every scheduler
utilization update (with the runqueue lock held) rather than being
throttled by rate_limit_us, even if the driver itself may skip redundant
hardware updates.
Clear need_freq_update at the end of the adjust_perf path as well.
Fixes: 75da043d8f ("cpufreq/sched: Set need_freq_update in ignore_dl_rate_limit()")
Signed-off-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Reviewed-by: Hongyan Xia <hongyan.xia@transsion.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Cc: All applicable <stable@vger.kernel.org>
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20260616154733.2405236-1-zhongqiu.han@oss.qualcomm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Linus Torvalds
Gabriele MonacoandPeter Zijlstra
Zhongqiu HanandRafael J. Wysocki
Kuba PiecuchandTejun Heo
Andrea RighiandTejun Heo
Breno LeitaoandTejun Heo
Rik van RielandThomas Gleixner