linux-stable.git/kernel/cgroup, branch v7.0.10

cgroup/cpuset: Return only actually allocated CPUs during partition invalidation

2026-05-23T11:09:37+00:00

commit 345f40166694e60db6d5cf02233814bb27ac5dec upstream.

In update_parent_effective_cpumask() with partcmd_invalidate, the CPUs
to return to the parent are computed as:

    adding = cpumask_and(tmp->addmask, xcpus, parent->effective_xcpus);

where xcpus = user_xcpus(cs) which returns cs->exclusive_cpus (if set)
or cs->cpus_allowed. When exclusive_cpus is not set, user_xcpus(cs) can
contain CPUs that were never actually granted to the partition due to
sibling exclusion in compute_excpus(). Consequently, the invalidation
may return CPUs to the parent that remain in use by sibling partitions,
causing overlapping effective_cpus and triggering the
WARN_ON_ONCE(1) in generate_sched_domains().

Use cs->effective_xcpus instead, which reflects the CPUs actually
granted to this partition.

Reproducer (on a 4-CPU machine):

    cd /sys/fs/cgroup
    mkdir a1 b1

    # a1 becomes partition root with CPUs 0-1
    echo "0-1" > a1/cpuset.cpus
    echo "root" > a1/cpuset.cpus.partition

    # b1 becomes partition root with CPUs 1-2, but sibling exclusion
    # reduces its effective_xcpus to CPU 2 only
    echo "1-2" > b1/cpuset.cpus
    echo "root" > b1/cpuset.cpus.partition

    # b1 changes cpus_allowed to 0-1 -> partition invalidation
    echo "0-1" > b1/cpuset.cpus

    # Expected: CPUs 2-3  (only CPU 2 returned from b1)
    # Actual:   CPUs 1-3  (CPU 0-1 returned, overlapping with a1)
    cat cpuset.cpus.effective

dmesg will also show a WARNING from generate_sched_domains() reporting
overlapping partition root effective_cpus.

Fixes: 2a3602030d80 ("cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict")
Cc: stable@vger.kernel.org # v7.0+
Signed-off-by: sunshaojie 
Tested-by: Chen Ridong 
Reviewed-by: Chen Ridong 
Reviewed-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

cgroup/cpuset: Reserve DL bandwidth only for root-domain moves

2026-05-23T11:09:37+00:00

commit 5dd74441cbf42c22e874450eb6a6bbb19390a216 upstream.

cpuset_can_attach() currently adds the bandwidth of all migrating
SCHED_DEADLINE tasks to sum_migrate_dl_bw. If the source and destination
cpuset effective CPU masks do not overlap, the whole sum is then
reserved in the destination root domain.

set_cpus_allowed_dl(), however, subtracts bandwidth from the source
root domain only when the affinity change really moves the task between
root domains. A DL task can move between cpusets that are still in the
same root domain, so including that task in sum_migrate_dl_bw can reserve
destination bandwidth without a matching source-side subtraction.

Share the root-domain move test with set_cpus_allowed_dl(). Keep
nr_migrate_dl_tasks counting all migrating deadline tasks for cpuset DL
task accounting, but add to sum_migrate_dl_bw only for tasks that need a
root-domain bandwidth move. Keep using the destination cpuset effective
CPU mask and leave the broader can_attach()/attach() transaction model
unchanged.

Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Cc: stable@vger.kernel.org # v6.10+
Signed-off-by: Guopeng Zhang 
Reviewed-by: Waiman Long 
Acked-by: Juri Lelli 
Tested-by: Juri Lelli 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

cgroup/dmem: Return -ENOMEM on failed pool preallocation

2026-05-23T11:09:37+00:00

commit 796ad622040f7f955ccc3973085e953415920496 upstream.

get_cg_pool_unlocked() handles allocation failures under dmemcg_lock by
dropping the lock, preallocating a pool with GFP_KERNEL, and retrying the
locked lookup and creation path.

If the fallback allocation fails too, pool remains NULL. Since the loop
condition is while (!pool), the function can keep retrying instead of
propagating the allocation failure to the caller.

Set pool to ERR_PTR(-ENOMEM) when the fallback allocation fails so the
loop exits through the existing common return path. The callers already
handle ERR_PTR() from get_cg_pool_unlocked(), so this restores the
expected error path.

Fixes: b168ed458dde ("kernel/cgroup: Add "dmem" memory accounting cgroup")
Cc: stable@vger.kernel.org # v6.14+
Signed-off-by: Guopeng Zhang 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

cgroup/cpuset: Reset DL migration state on can_attach() failure

2026-05-23T11:09:36+00:00

commit 4a39eda5fdd867fc39f3c039714dd432cee00268 upstream.

cpuset_can_attach() accumulates temporary SCHED_DEADLINE migration
state in the destination cpuset while walking the taskset.

If a later task_can_attach() or security_task_setscheduler() check
fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
and does not call cpuset_cancel_attach() for it. The partially
accumulated state is then left behind and can be consumed by a later
attach, corrupting cpuset DL task accounting and pending DL bandwidth
accounting.

Reset the pending DL migration state from the common error exit when
ret is non-zero. Successful can_attach() keeps the state for
cpuset_attach() or cpuset_cancel_attach().

Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Cc: stable@vger.kernel.org # v6.10+
Signed-off-by: Guopeng Zhang 
Signed-off-by: Tejun Heo 
Reviewed-by: Chen Ridong 
Reviewed-by: Waiman Long 
Signed-off-by: Greg Kroah-Hartman

cgroup/cpuset: record DL BW alloc CPU for attach rollback

2026-05-23T11:09:25+00:00

[ Upstream commit 41d701ddc36d5301b44ea79529f3cf03c541c1e1 ]

cpuset_can_attach() allocates DL bandwidth only when migrating
deadline tasks to a disjoint CPU mask, but cpuset_cancel_attach()
rolls back based only on nr_migrate_dl_tasks. This makes the DL
bandwidth alloc/free paths asymmetric: rollback can call dl_bw_free()
even when no dl_bw_alloc() was done.

Rollback also needs to undo the reservation against the same CPU/root
domain that was charged. Record the CPU used by dl_bw_alloc() and use
that state in cpuset_cancel_attach(). If no allocation happened,
dl_bw_cpu stays at -1 and rollback skips dl_bw_free(). If allocation
did happen, bandwidth is returned to the same CPU/root domain.

Successful attach paths are unchanged. This only fixes failed attach
rollback accounting.

Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Signed-off-by: Guopeng Zhang 
Reviewed-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup/rdma: fix integer overflow in rdmacg_try_charge()

2026-05-23T11:09:25+00:00

[ Upstream commit c802f460dd485c1332b5a35e7adcfb2bc22536a2 ]

The expression `rpool->resources[index].usage + 1` is computed in int
arithmetic before being assigned to s64 variable `new`. When usage equals
INT_MAX (the default "max" value), the addition overflows to INT_MIN.
This negative value then passes the `new > max` check incorrectly,
allowing a charge that should be rejected and corrupting usage to
negative.

Fix by casting usage to s64 before the addition so the arithmetic is
done in 64-bit.

Fixes: 39d3e7584a68 ("rdmacg: Added rdma cgroup controller")
Signed-off-by: cuitao 
Reviewed-by: Michal Koutný 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

sched/psi: fix race between file release and pressure write

2026-05-23T11:09:25+00:00

[ Upstream commit a5b98009f16d8a5fb4a8ff9a193f5735515c38fa ]

A potential race condition exists between pressure write and cgroup file
release regarding the priv member of struct kernfs_open_file, which
triggers the uaf reported in [1].

Consider the following scenario involving execution on two separate CPUs:

   CPU0					CPU1
   ====					====
					vfs_rmdir()
					kernfs_iop_rmdir()
					cgroup_rmdir()
					cgroup_kn_lock_live()
					cgroup_destroy_locked()
					cgroup_addrm_files()
					cgroup_rm_file()
					kernfs_remove_by_name()
					kernfs_remove_by_name_ns()
 vfs_write()				__kernfs_remove()
 new_sync_write()			kernfs_drain()
 kernfs_fop_write_iter()		kernfs_drain_open_files()
 cgroup_file_write()			kernfs_release_file()
 pressure_write()			cgroup_file_release()
 ctx = of->priv;
					kfree(ctx);
 					of->priv = NULL;
					cgroup_kn_unlock()
 cgroup_kn_lock_live()
 cgroup_get(cgrp)
 cgroup_kn_unlock()
 if (ctx->psi.trigger)  // here, trigger uaf for ctx, that is of->priv

The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards
the memory deallocation of of->priv performed within cgroup_file_release().
However, the operations involving of->priv executed within pressure_write()
are not entirely covered by the protection of cgroup_mutex. Consequently,
if the code in pressure_write(), specifically the section handling the
ctx variable executes after cgroup_file_release() has completed, a uaf
vulnerability involving of->priv is triggered.

Therefore, the issue can be resolved by extending the scope of the
cgroup_mutex lock within pressure_write() to encompass all code paths
involving of->priv, thereby properly synchronizing the race condition
occurring between cgroup_file_release() and pressure_write().

And, if an live kn lock can be successfully acquired while executing
the pressure write operation, it indicates that the cgroup deletion
process has not yet reached its final stage; consequently, the priv
pointer within open_file cannot be NULL. Therefore, the operation to
retrieve the ctx value must be moved to a point *after* the live kn
lock has been successfully acquired.

In another situation, specifically after entering cgroup_kn_lock_live()
but before acquiring cgroup_mutex, there exists a different class of
race condition:

CPU0: write memory.pressure               CPU1: write cgroup.pressure=0
===========================		  =============================

kernfs_fop_write_iter()
 kernfs_get_active_of(of)
 pressure_write()
   cgroup_kn_lock_live(memory.pressure)
     cgroup_tryget(cgrp)
     kernfs_break_active_protection(kn)
     ... blocks on cgroup_mutex

                                     	  cgroup_pressure_write()
                                     	  cgroup_kn_lock_live(cgroup.pressure)
                                     	  cgroup_file_show(memory.pressure, false)
                                     	    kernfs_show(false)
                                     	      kernfs_drain_open_files()
                                     	        cgroup_file_release(of)
                                     	          kfree(ctx)
                                     	            of->priv = NULL
                                     	  cgroup_kn_unlock()

   ... acquires cgroup_mutex
   ctx = of->priv;        // may now be NULL
   if (ctx->psi.trigger)  // NULL dereference

Consequently, there is a possibility that of->priv is NULL, the pressure
write needs to check for this.

Now that the scope of the cgroup_mutex has been expanded, the original
explicit cgroup_get/put operations are no longer necessary, this is
because acquiring/releasing the live kn lock inherently executes a
cgroup get/put operation.

[1]
BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011
Call Trace:
 pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011
 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:4311
 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352

Allocated by task 9352:
 cgroup_file_open+0x90/0x3a0 kernel/cgroup/cgroup.c:4256
 kernfs_fop_open+0x9eb/0xcb0 fs/kernfs/file.c:724
 do_dentry_open+0x83d/0x13e0 fs/open.c:949

Freed by task 9353:
 cgroup_file_release+0xd6/0x100 kernel/cgroup/cgroup.c:4283
 kernfs_release_file fs/kernfs/file.c:764 [inline]
 kernfs_drain_open_files+0x392/0x720 fs/kernfs/file.c:834
 kernfs_drain+0x470/0x600 fs/kernfs/dir.c:525

Fixes: 0e94682b73bf ("psi: introduce psi monitor")
Reported-by: syzbot+33e571025d88efd1312c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=33e571025d88efd1312c
Tested-by: syzbot+33e571025d88efd1312c@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis 
Reviewed-by: Chen Ridong 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup: Defer css percpu_ref kill on rmdir until cgroup is depopulated

2026-05-17T15:16:33+00:00

[ Upstream commit 93618edf753838a727dbff63c7c291dee22d656b ]

A chain of commits going back to v7.0 reworked rmdir to satisfy the
controller invariant that a subsystem's ->css_offline() must not run while
tasks are still doing kernel-side work in the cgroup.

[1] d245698d727a ("cgroup: Defer task cgroup unlink until after the task is done switching out")
[2] a72f73c4dd9b ("cgroup: Don't expose dead tasks in cgroup")
[3] 1b164b876c36 ("cgroup: Wait for dying tasks to leave on rmdir")
[4] 4c56a8ac6869 ("cgroup: Fix cgroup_drain_dying() testing the wrong condition")
[5] 13e786b64bd3 ("cgroup: Increment nr_dying_subsys_* from rmdir context")

[1] moved task cset unlink from do_exit() to finish_task_switch() so a
task's cset link drops only after the task has fully stopped scheduling.
That made tasks past exit_signals() linger on cset->tasks until their final
context switch, which led to a series of problems as what userspace expected
to see after rmdir diverged from what the kernel needs to wait for. [2]-[5]
tried to bridge that divergence: [2] filtered the exiting tasks from
cgroup.procs; [3] had rmdir(2) sleep in TASK_UNINTERRUPTIBLE for them; [4]
fixed the wait's condition; [5] made nr_dying_subsys_* visible
synchronously.

The cgroup_drain_dying() wait in [3] turned out to be a dead end. When the
rmdir caller is also the reaper of a zombie that pins a pidns teardown (e.g.
host PID 1 systemd reaping orphan pids that were re-parented to it during
the same teardown), rmdir blocks in TASK_UNINTERRUPTIBLE waiting for those
pids to free, the pids can't free because PID 1 is the reaper and it's stuck
in rmdir, and the system A-A deadlocks. No internal lock ordering breaks
this; the wait itself is the bug.

The css killing side that drove the original reorder, however, can be made
cleanly asynchronous: ->css_offline() is already async, run from
css_killed_work_fn() driven by percpu_ref_kill_and_confirm(). The fix is to
make that chain start only after all tasks have left the cgroup. rmdir's
user-visible side then returns as soon as cgroup.procs and friends are
empty, while ->css_offline() still runs only after the cgroup is fully
drained.

Verified by the original reproducer (pidns teardown + zombie reaper, runs
under vng) which hangs vanilla and succeeds here, and by per-commit
deterministic repros for [2], [3], [4], [5] with a boot parameter that
widens the post-exit_signals() window so each state is reliably reachable.
Some stress tests on top of that.

cgroup_apply_control_disable() has the same shape of pre-existing race:
when a controller is disabled via subtree_control, kill_css() ran
synchronously while tasks past exit_signals() could still be linked to
the cgroup's csets, and ->css_offline() could fire before they drained.
This patch preserves the existing synchronous behavior at that call site
(kill_css_sync() + kill_css_finish() back-to-back) and a follow-up patch
will defer kill_css_finish() there using a per-css trigger.

This seems like the right approach and I don't see problems with it. The
changes are somewhat invasive but not excessively so, so backporting to
-stable should be okay. If something does turn out to be wrong, the fallback
is to revert the entire chain ([1]-[5]) and rework in the development branch
instead.

v2: Pin cgrp across the deferred destroy work with explicit
    cgroup_get()/cgroup_put() around queue_work() and the work_fn. v1
    wasn't actually broken (ordered cgroup_offline_wq + queue_work order
    in cgroup_task_dead() saved it) but the explicit ref removes the
    dependency on those non-obvious invariants. Also note the
    pre-existing cgroup_apply_control_disable() race in the description;
    a follow-up will defer kill_css_finish() there.

Fixes: 1b164b876c36 ("cgroup: Wait for dying tasks to leave on rmdir")
Cc: stable@vger.kernel.org # v7.0+
Reported-and-tested-by: Martin Pitt 
Link: https://lore.kernel.org/all/afHNg2VX2jy9bW7y@piware.de/
Link: https://lore.kernel.org/all/35e0670adb4abeab13da2c321582af9f@kernel.org/
Signed-off-by: Tejun Heo 
Acked-by: Sebastian Andrzej Siewior 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

cgroup: Increment nr_dying_subsys_* from rmdir context

2026-05-17T15:16:33+00:00

[ Upstream commit 13e786b64bd3fd81c7eb22aa32bf8305c32f2ccf ]

Incrementing nr_dying_subsys_* in offline_css(), which is executed by
cgroup_offline_wq worker, leads to a race where user can see the value
to be 0 if he reads cgroup.stat after calling rmdir and before the worker
executes. This makes the user wrongly expect resources released by the
removed cgroup to be available for a new assignment.

Increment nr_dying_subsys_* from kill_css(), which is called from the
cgroup_rmdir() context.

Fixes: ab0312526867 ("cgroup: Show # of subsystem CSSes in cgroup.stat")
Signed-off-by: Petr Malat 
Signed-off-by: Tejun Heo 
Stable-dep-of: 93618edf7538 ("cgroup: Defer css percpu_ref kill on rmdir until cgroup is depopulated")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

cgroup/cpuset: Skip security check for hotplug induced v1 task migration

2026-03-31T19:14:13+00:00

When a CPU hot removal causes a v1 cpuset to lose all its CPUs, the
cpuset hotplug handler will schedule a work function to migrate tasks
in that cpuset with no CPU to its ancestor to enable those tasks to
continue running.

If a strict security policy is in place, however, the task migration
may fail when security_task_setscheduler() call in cpuset_can_attach()
returns a -EACCES error. That will mean that those tasks will have
no CPU to run on. The system administrators will have to explicitly
intervene to either add CPUs to that cpuset or move the tasks elsewhere
if they are aware of it.

This problem was found by a reported test failure in the LTP's
cpuset_hotplug_test.sh. Fix this problem by treating this special case as
an exception to skip the setsched security check in cpuset_can_attach()
when a v1 cpuset with tasks have no CPU left.

With that patch applied, the cpuset_hotplug_test.sh test can be run
successfully without failure.

Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo