kernel.git/kernel/cgroup/cgroup.c, branch linux-rolling-stable

cgroup: Don't expose dead tasks in cgroup

2026-03-19T15:14:59Z

commit a72f73c4dd9b209c53cf8b03b6e97fcefad4262c upstream. Once a task exits it has its state set to TASK_DEAD and then it is removed from the cgroup it belonged to. The last step happens on the task gets out of its last schedule() invocation and is delayed on PREEMPT_RT due to locking constraints. As a result it is possible to receive a pid via waitpid() of a task which is still listed in cgroup.procs for the cgroup it belonged to. This is something that systemd does not expect and as a result it waits for its exit until a time out occurs. This can also be reproduced on !PREEMPT_RT kernel with a significant delay in do_exit() after exit_notify(). Hide the task from the output which have PF_EXITING set which is done before the parent is notified. Keeping zombies with live threads shouldn't break anything (suggested by Tejun). Reported-by: Bert Karwatzki Closes: https://lore.kernel.org/all/20260219164648.3014-1-spasswolf@web.de/ Tested-by: Bert Karwatzki Fixes: 9311e6c29b34 ("cgroup: Fix sleeping from invalid context warning on PREEMPT_RT") Cc: stable@vger.kernel.org # v6.19+ Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

cgroup: fix race between task migration and iteration

2026-03-19T15:14:59Z

commit 5ee01f1a7343d6a3547b6802ca2d4cdce0edacb1 upstream. When a task is migrated out of a css_set, cgroup_migrate_add_task() first moves it from cset->tasks to cset->mg_tasks via: list_move_tail(&task->cg_list, &cset->mg_tasks); If a css_task_iter currently has it->task_pos pointing to this task, css_set_move_task() calls css_task_iter_skip() to keep the iterator valid. However, since the task has already been moved to ->mg_tasks, the iterator is advanced relative to the mg_tasks list instead of the original tasks list. As a result, remaining tasks on cset->tasks, as well as tasks queued on cset->mg_tasks, can be skipped by iteration. Fix this by calling css_set_skip_task_iters() before unlinking task->cg_list from cset->tasks. This advances all active iterators to the next task on cset->tasks, so iteration continues correctly even when a task is concurrently being migrated. This race is hard to hit in practice without instrumentation, but it can be reproduced by artificially slowing down cgroup_procs_show(). For example, on an Android device a temporary /sys/kernel/cgroup/cgroup_test knob can be added to inject a delay into cgroup_procs_show(), and then: 1) Spawn three long-running tasks (PIDs 101, 102, 103). 2) Create a test cgroup and move the tasks into it. 3) Enable a large delay via /sys/kernel/cgroup/cgroup_test. 4) In one shell, read cgroup.procs from the test cgroup. 5) Within the delay window, in another shell migrate PID 102 by writing it to a different cgroup.procs file. Under this setup, cgroup.procs can intermittently show only PID 101 while skipping PID 103. Once the migration completes, reading the file again shows all tasks as expected. Note that this change does not allow removing the existing css_set_skip_task_iters() call in css_set_move_task(). The new call in cgroup_migrate_add_task() only handles iterators that are racing with migration while the task is still on cset->tasks. Iterators may also start after the task has been moved to cset->mg_tasks. If we dropped css_set_skip_task_iters() from css_set_move_task(), such iterators could keep task_pos pointing to a migrating task, causing css_task_iter_advance() to malfunction on the destination css_set, up to and including crashes or infinite loops. The race window between migration and iteration is very small, and css_task_iter is not on a hot path. In the worst case, when an iterator is positioned on the first thread of the migrating process, cgroup_migrate_add_task() may have to skip multiple tasks via css_set_skip_task_iters(). However, this only happens when migration and iteration actually race, so the performance impact is negligible compared to the correctness fix provided here. Fixes: b636fd38dc40 ("cgroup: Implement css_task_iter_skip()") Cc: stable@vger.kernel.org # v5.2+ Signed-off-by: Qingye Zhao Reviewed-by: Michal Koutný Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

kernel: cgroup: Add SPDX-License-Identifier lines

2026-01-16T08:03:09Z

Add GPL-2.0 SPDX license id lines to a few old files, replacing the reference to the COPYING file. The COPYING file at the time of creation of these files (2007 and 2005) was GPL-v2.0, with an additional clause indicating that only v2 applied. Signed-off-by: Tim Bird Signed-off-by: Tejun Heo

cgroup: Eliminate cgrp_ancestor_storage in cgroup_root

2026-01-08T01:11:03Z

The cgrp_ancestor_storage has two drawbacks: - it's not guaranteed that the member immediately follows struct cgrp in cgroup_root (root cgroup's ancestors[0] might thus point to a padding and not in cgrp_ancestor_storage proper), - this idiom raises warnings with -Wflex-array-member-not-at-end. Instead of relying on the auxiliary member in cgroup_root, define the 0-th level ancestor inside struct cgroup (needed for static allocation of cgrp_dfl_root), deeper cgroups would allocate flexible _low_ancestors[]. Unionized alias through ancestors[] will transparently join the two ranges. The above change would still leave the flexible array at the end of struct cgroup inside cgroup_root, so move cgrp also towards the end of cgroup_root to resolve the -Wflex-array-member-not-at-end. Link: https://lore.kernel.org/r/5fb74444-2fbb-476e-b1bf-3f3e279d0ced@embeddedor.com/ Reported-by: Gustavo A. R. Silva Closes: https://lore.kernel.org/r/b3eb050d-9451-4b60-b06c-ace7dab57497@embeddedor.com/ Cc: David Laight Acked-by: Gustavo A. R. Silva Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo

Merge tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-12-05T21:52:43Z

Pull MM updates from Andrew Morton: "__vmalloc()/kvmalloc() and no-block support" (Uladzislau Rezki) Rework the vmalloc() code to support non-blocking allocations (GFP_ATOIC, GFP_NOWAIT) "ksm: fix exec/fork inheritance" (xu xin) Fix a rare case where the KSM MMF_VM_MERGE_ANY prctl state is not inherited across fork/exec "mm/zswap: misc cleanup of code and documentations" (SeongJae Park) Some light maintenance work on the zswap code "mm/page_owner: add debugfs files 'show_handles' and 'show_stacks_handles'" (Mauricio Faria de Oliveira) Enhance the /sys/kernel/debug/page_owner debug feature by adding unique identifiers to differentiate the various stack traces so that userspace monitoring tools can better match stack traces over time "mm/page_alloc: pcp->batch cleanups" (Joshua Hahn) Minor alterations to the page allocator's per-cpu-pages feature "Improve UFFDIO_MOVE scalability by removing anon_vma lock" (Lokesh Gidra) Address a scalability issue in userfaultfd's UFFDIO_MOVE operation "kasan: cleanups for kasan_enabled() checks" (Sabyrzhan Tasbolatov) "drivers/base/node: fold node register and unregister functions" (Donet Tom) Clean up the NUMA node handling code a little "mm: some optimizations for prot numa" (Kefeng Wang) Cleanups and small optimizations to the NUMA allocation hinting code "mm/page_alloc: Batch callers of free_pcppages_bulk" (Joshua Hahn) Address long lock hold times at boot on large machines. These were causing (harmless) softlockup warnings "optimize the logic for handling dirty file folios during reclaim" (Baolin Wang) Remove some now-unnecessary work from page reclaim "mm/damon: allow DAMOS auto-tuned for per-memcg per-node memory usage" (SeongJae Park) Enhance the DAMOS auto-tuning feature "mm/damon: fixes for address alignment issues in DAMON_LRU_SORT and DAMON_RECLAIM" (Quanmin Yan) Fix DAMON_LRU_SORT and DAMON_RECLAIM with certain userspace configuration "expand mmap_prepare functionality, port more users" (Lorenzo Stoakes) Enhance the new(ish) file_operations.mmap_prepare() method and port additional callsites from the old ->mmap() over to ->mmap_prepare() "Fix stale IOTLB entries for kernel address space" (Lu Baolu) Fix a bug (and possible security issue on non-x86) in the IOMMU code. In some situations the IOMMU could be left hanging onto a stale kernel pagetable entry "mm/huge_memory: cleanup __split_unmapped_folio()" (Wei Yang) Clean up and optimize the folio splitting code "mm, swap: misc cleanup and bugfix" (Kairui Song) Some cleanups and a minor fix in the swap discard code "mm/damon: misc documentation fixups" (SeongJae Park) "mm/damon: support pin-point targets removal" (SeongJae Park) Permit userspace to remove a specific monitoring target in the middle of the current targets list "mm: MISC follow-up patches for linux/pgalloc.h" (Harry Yoo) A couple of cleanups related to mm header file inclusion "mm/swapfile.c: select swap devices of default priority round robin" (Baoquan He) improve the selection of swap devices for NUMA machines "mm: Convert memory block states (MEM_*) macros to enums" (Israel Batista) Change the memory block labels from macros to enums so they will appear in kernel debug info "ksm: perform a range-walk to jump over holes in break_ksm" (Pedro Demarchi Gomes) Address an inefficiency when KSM unmerges an address range "mm/damon/tests: fix memory bugs in kunit tests" (SeongJae Park) Fix leaks and unhandled malloc() failures in DAMON userspace unit tests "some cleanups for pageout()" (Baolin Wang) Clean up a couple of minor things in the page scanner's writeback-for-eviction code "mm/hugetlb: refactor sysfs/sysctl interfaces" (Hui Zhu) Move hugetlb's sysfs/sysctl handling code into a new file "introduce VM_MAYBE_GUARD and make it sticky" (Lorenzo Stoakes) Make the VMA guard regions available in /proc/pid/smaps and improves the mergeability of guarded VMAs "mm: perform guard region install/remove under VMA lock" (Lorenzo Stoakes) Reduce mmap lock contention for callers performing VMA guard region operations "vma_start_write_killable" (Matthew Wilcox) Start work on permitting applications to be killed when they are waiting on a read_lock on the VMA lock "mm/damon/tests: add more tests for online parameters commit" (SeongJae Park) Add additional userspace testing of DAMON's "commit" feature "mm/damon: misc cleanups" (SeongJae Park) "make VM_SOFTDIRTY a sticky VMA flag" (Lorenzo Stoakes) Address the possible loss of a VMA's VM_SOFTDIRTY flag when that VMA is merged with another "mm: support device-private THP" (Balbir Singh) Introduce support for Transparent Huge Page (THP) migration in zone device-private memory "Optimize folio split in memory failure" (Zi Yan) "mm/huge_memory: Define split_type and consolidate split support checks" (Wei Yang) Some more cleanups in the folio splitting code "mm: remove is_swap_[pte, pmd]() + non-swap entries, introduce leaf entries" (Lorenzo Stoakes) Clean up our handling of pagetable leaf entries by introducing the concept of 'software leaf entries', of type softleaf_t "reparent the THP split queue" (Muchun Song) Reparent the THP split queue to its parent memcg. This is in preparation for addressing the long-standing "dying memcg" problem, wherein dead memcg's linger for too long, consuming memory resources "unify PMD scan results and remove redundant cleanup" (Wei Yang) A little cleanup in the hugepage collapse code "zram: introduce writeback bio batching" (Sergey Senozhatsky) Improve zram writeback efficiency by introducing batched bio writeback support "memcg: cleanup the memcg stats interfaces" (Shakeel Butt) Clean up our handling of the interrupt safety of some memcg stats "make vmalloc gfp flags usage more apparent" (Vishal Moola) Clean up vmalloc's handling of incoming GFP flags "mm: Add soft-dirty and uffd-wp support for RISC-V" (Chunyan Zhang) Teach soft dirty and userfaultfd write protect tracking to use RISC-V's Svrsw60t59b extension "mm: swap: small fixes and comment cleanups" (Youngjun Park) Fix a small bug and clean up some of the swap code "initial work on making VMA flags a bitmap" (Lorenzo Stoakes) Start work on converting the vma struct's flags to a bitmap, so we stop running out of them, especially on 32-bit "mm/swapfile: fix and cleanup swap list iterations" (Youngjun Park) Address a possible bug in the swap discard code and clean things up a little [ This merge also reverts commit ebb9aeb980e5 ("vfio/nvgrace-gpu: register device memory for poison handling") because it looks broken to me, I've asked for clarification - Linus ] * tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits) mm: fix vma_start_write_killable() signal handling mm/swapfile: use plist_for_each_entry in __folio_throttle_swaprate mm/swapfile: fix list iteration when next node is removed during discard fs/proc/task_mmu.c: fix make_uffd_wp_huge_pte() huge pte handling mm/kfence: add reboot notifier to disable KFENCE on shutdown memcg: remove inc/dec_lruvec_kmem_state helpers selftests/mm/uffd: initialize char variable to Null mm: fix DEBUG_RODATA_TEST indentation in Kconfig mm: introduce VMA flags bitmap type tools/testing/vma: eliminate dependency on vma->__vm_flags mm: simplify and rename mm flags function for clarity mm: declare VMA flags by bit zram: fix a spelling mistake mm/page_alloc: optimize lowmem_reserve max lookup using its semantic monotonicity mm/vmscan: skip increasing kswapd_failures when reclaim was boosted pagemap: update BUDDY flag documentation mm: swap: remove scan_swap_map_slots() references from comments mm: swap: change swap_alloc_slow() to void mm, swap: remove redundant comment for read_swap_cache_async mm, swap: use SWP_SOLIDSTATE to determine if swap is rotational ...

Merge tag 'cgroup-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2025-12-03T21:04:07Z

Pull cgroup updates from Tejun Heo: - Defer task cgroup unlink until after the dying task's final context switch so that controllers see the cgroup properly populated until the task is truly gone - cpuset cleanups and simplifications. Enforce that domain isolated CPUs stay in root or isolated partitions and fail if isolated+nohz_full would leave no housekeeping CPU. Fix sched/deadline root domain handling during CPU hot-unplug and race for tasks in attaching cpusets - Misc fixes including memory reclaim protection documentation and selftest KTAP conformance * tag 'cgroup-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits) cpuset: Treat cpusets in attaching as populated sched/deadline: Walk up cpuset hierarchy to decide root domain when hot-unplug cgroup/cpuset: Introduce cpuset_cpus_allowed_locked() docs: cgroup: No special handling of unpopulated memcgs docs: cgroup: Note about sibling relative reclaim protection docs: cgroup: Explain reclaim protection target selftests/cgroup: conform test to KTAP format output cpuset: remove need_rebuild_sched_domains cpuset: remove global remote_children list cpuset: simplify node setting on error cgroup: include missing header for struct irq_work cgroup: Fix sleeping from invalid context warning on PREEMPT_RT cgroup/cpuset: Globally track isolated_cpus update cgroup/cpuset: Ensure domain isolated CPUs stay in root or isolated partition cgroup/cpuset: Move up prstate_housekeeping_conflict() helper cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_isolation_cpumasks() cgroup: Defer task cgroup unlink until after the task is done switching out cgroup: Move dying_tasks cleanup from cgroup_task_release() to cgroup_task_free() cgroup: Rename cgroup lifecycle hooks to cgroup_task_*() ...

Merge tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-01T21:45:41Z

Pull cred guard updates from Christian Brauner: "This contains substantial credential infrastructure improvements adding guard-based credential management that simplifies code and eliminates manual reference counting in many subsystems. Features: - Kernel Credential Guards Add with_kernel_creds() and scoped_with_kernel_creds() guards that allow using the kernel credentials without allocating and copying them. This was requested by Linus after seeing repeated prepare_kernel_creds() calls that duplicate the kernel credentials only to drop them again later. The new guards completely avoid the allocation and never expose the temporary variable to hold the kernel credentials anywhere in callers. - Generic Credential Guards Add scoped_with_creds() guards for the common override_creds() and revert_creds() pattern. This builds on earlier work that made override_creds()/revert_creds() completely reference count free. - Prepare Credential Guards Add prepare credential guards for the more complex pattern of preparing a new set of credentials and overriding the current credentials with them: - prepare_creds() - modify new creds - override_creds() - revert_creds() - put_cred() Cleanups: - Make init_cred static since it should not be directly accessed - Add kernel_cred() helper to properly access the kernel credentials - Fix scoped_class() macro that was introduced two cycles ago - coredump: split out do_coredump() from vfs_coredump() for cleaner credential handling - coredump: move revert_cred() before coredump_cleanup() - coredump: mark struct mm_struct as const - coredump: pass struct linux_binfmt as const - sev-dev: use guard for path" * tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (36 commits) trace: use override credential guard trace: use prepare credential guard coredump: use override credential guard coredump: use prepare credential guard coredump: split out do_coredump() from vfs_coredump() coredump: mark struct mm_struct as const coredump: pass struct linux_binfmt as const coredump: move revert_cred() before coredump_cleanup() sev-dev: use override credential guards sev-dev: use prepare credential guard sev-dev: use guard for path cred: add prepare credential guard net/dns_resolver: use credential guards in dns_query() cgroup: use credential guards in cgroup_attach_permissions() act: use credential guards in acct_write_process() smb: use credential guards in cifs_get_spnego_key() nfs: use credential guards in nfs_idmap_get_key() nfs: use credential guards in nfs_local_call_write() nfs: use credential guards in nfs_local_call_read() erofs: use credential guards ...

memcg: net: track network throttling due to memcg memory pressure

2025-11-17T01:28:06Z

The kernel can throttle network sockets if the memory cgroup associated with the corresponding socket is under memory pressure. The throttling actions include clamping the transmit window, failing to expand receive or send buffers, aggressively prune out-of-order receive queue, FIN deferred to a retransmitted packet and more. Let's add memcg metric to track such throttling actions. At the moment memcg memory pressure is defined through vmpressure and in future it may be defined using PSI or we may add more flexible way for the users to define memory pressure, maybe through ebpf. However the potential throttling actions will remain the same, so this newly introduced metric will continue to track throttling actions irrespective of how memcg memory pressure is defined. Link: https://lkml.kernel.org/r/20251016161035.86161-1-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Acked-by: Roman Gushchin Reviewed-by: Kuniyuki Iwashima Reviewed-by: Daniel Sedlak Cc: David S. Miller Cc: Eric Dumazet Cc: Jakub Kacinski Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Neal Cardwell Cc: Paolo Abeni Cc: Simon Horman Cc: Tejun Heo Cc: Willem de Bruijn Signed-off-by: Andrew Morton

cgroup: include missing header for struct irq_work

2025-11-11T18:52:42Z

To compile cgroup.c with PREEMPT_RT=y include header which declares struct irq_work. Fixes: 9311e6c29b34 ("cgroup: Fix sleeping from invalid context warning on PREEMPT_RT") Signed-off-by: Bert Karwatzki Signed-off-by: Tejun Heo

ns: drop custom reference count initialization for initial namespaces

2025-11-11T09:01:32Z

Initial namespaces don't modify their reference count anymore. They remain fixed at one so drop the custom refcount initializations. Link: https://patch.msgid.link/20251110-work-namespace-nstree-fixes-v1-16-e8a9264e0fb9@kernel.org Signed-off-by: Christian Brauner