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2026-09-17ALSA: seq: Serialize compat port-info ioctlsKyle Zeng1-1/+3
The native sequencer ioctl path serializes handler calls with client->ioctl_mutex, but the translated port-info compat path invokes the same handlers through snd_seq_kernel_client_ctl() without taking that mutex. This lets concurrent compat CREATE_PORT requests pass the port-count check before any request reaches the serialized insertion. The computed integer port index can then exceed the address field range and wrap to an existing index. Subsequent subscriber teardown can resolve the duplicate address to the wrong port and access a freed subscriber. Take ioctl_mutex while dispatching converted port-info requests, matching the native ioctl path. All translated port-info commands share this helper, so their accesses to the client port state are serialized as well. Fixes: b3defb791b26 ("ALSA: seq: Make ioctls race-free") Cc: stable@vger.kernel.org Assisted-by: Codex:gpt-5.6-sol gpt-6-astra Signed-off-by: Kyle Zeng <kylebot@openai.com> Signed-off-by: Bruno Produit <bruno.produit@trailofbits.com> Link: https://patch.msgid.link/20260917105643.90102-1-bruno.produit@trailofbits.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-09-17Merge tag 'asoc-fix-v7.3-rc3' of ↵Takashi Iwai11-14/+14
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus ASoC: Fixes for v7.3 A relatively large pile of fixes here, a lot of driver specific stuff that's broadly unremarkable plus a few core fixes from Richard that fix issues where SoundWire systems with multiple CODECs on the same link would configure the CODECs to use the same bus slots leading to broken audio.
2026-09-13ALSA: pcm: set timer->private_data before registering the PCM timerNguyen Ngoc Thang1-2/+5
snd_pcm_timer_init() calls snd_device_register() to link the new struct snd_timer into the global timer list while it still carries hw.c_resolution = snd_pcm_timer_resolution (and hw.start/hw.stop), and only afterwards sets timer->private_data = substream. Once the timer is on the list under register_mutex, a concurrent reader can already reach it through the same mutex and invoke these callbacks. /proc/asound/timers does this via c_resolution(), and snd_timer_open()+snd_timer_start() reach start()/stop() the same way. All three dereference timer->private_data, which for this brief window is NULL, giving a NULL-pointer dereference: substream = timer->private_data; return substream->runtime ? ... // substream is NULL Move the private_data/private_free assignment before snd_device_register() so the timer is never visible on the list without its private_data set. On the snd_device_register() failure path, private_free() (snd_pcm_timer_free()) can now run, but it only does substream->timer = NULL, which is already NULL at that point since substream->timer is set to the new timer just once, after a successful registration -- so the failure path stays safe. Reported-by: syzbot+19da64013c46df87f971@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=19da64013c46df87f971 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com> Link: https://patch.msgid.link/20260913134446.114724-1-ngocthang2710.1999@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-09-13ALSA: core: Fix potential UAF after asynchronous card releaseTakashi Iwai1-1/+2
Usually a sound driver releases the resources assigned to the card via snd_card_free(), and it synchronizes with the whole release procedure. However, when the card is released asynchronously via snd_card_free_when_closed() like USB-audio driver, the situation is slightly different; although the snd_card_disconnect() call at the disconnection guarantees that any newer accesses will be gated, the in-flight tasks might be still accessing to the underlying card->dev device even after the disconnection, which would cause a use-after-free in the end, as reported by fuzzers. For addressing the bug above, this patch takes the refcount of card->dev at initialization of the card object, and releases at its destructor. This assures the availability of the card->dev in its whole lifecycle. Reported-by: Farhad Alemi <farhad.alemi@berkeley.edu> Closes: https://lore.kernel.org/CA+0ovChexj4TrZL_2iG_P0WBEbZc5+73GfB3DkciQi=R8pZOnA@mail.gmail.com Closes: https://lore.kernel.org/CA+0ovCgQUQNN=Z1tJTouiCsDaXR5M-3-SQEGk-cpPXQkM5Xh+w@mail.gmail.com Cc: <stable@vger.kernel.org> Link: https://patch.msgid.link/20260912162150.455144-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-09-04treewide: refresh kmalloc_obj() conversionsKees Cook11-14/+14
This is another run of the Coccinelle script for converting kmalloc() family of allocations to kmalloc_obj() via the existing rules in scripts/coccinelle/api/kmalloc_objs.cocci This catches both the set of kmalloc() uses added since the first kmalloc_obj() conversions in v7.0 and adds a large group missed in the first pass due to Coccinelle not interacting well with the cleanup.h scoped_...() family of macros[1]. I worked around this with spatch's "--macro-file" argument to a file with all the scoped_...() macros mapped to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control flow indicator I could find. Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc, riscv, and s390 with no new warnings. Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1] Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2] Signed-off-by: Kees Cook <kees+treewide@kernel.org>
2026-09-02ALSA: rawmidi: Return the error from snd_rawmidi_input_params()HyeongJun An1-1/+1
The snd_rawmidi_input_params() computes err for the three invalid mode combinations and for resize_runtime_buffer(), applies the new framing and clock type only when err is zero, and then returns 0 anyway. A caller that asked for parameters the kernel rejected is told the change succeeded, and the substream keeps its old buffer. The open_mutex conversion turned the early returns into assignments. It handled the output sibling correctly, which still returns err, and left this one behind. Fixes: 94b98194b62e ("ALSA: rawmidi: Take open_mutex around parameter changes") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-5 Signed-off-by: HyeongJun An <sammiee5311@gmail.com> Link: https://patch.msgid.link/20260902125058.19499-1-sammiee5311@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-09-02ALSA: ump: do not touch legacy_rmidi before it existsQingyu Zhang1-0/+4
snd_ump_parse_endpoint() sets ump->parsed on every exit, including error, before the caller attaches the legacy rawmidi device. ump_handle_ep_name_msg() then treats parsed as "legacy_rmidi is live" and calls ump_legacy_set_rawmidi_name(), which snprintf()s into ump->legacy_rmidi->name. If a UMP packet arrives in that window (IRQ path from snd_ump_receive), legacy_rmidi is still NULL (KASAN null-ptr-deref in snprintf). Guard the legacy helpers. parsed only means endpoint info was parsed, not that legacy_rmidi exists. Fixes: 37e0e14128e0 ("ALSA: ump: Support UMP Endpoint and Function Block parsing") Signed-off-by: Qingyu Zhang <usupergate@gmail.com> Link: https://patch.msgid.link/20260902073918.880245-1-usupergate@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-31ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAFYilin Zhang1-10/+25
snd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation with an mmap_count check performed under the PCM stream lock, but the lock is released long before the buffer is actually freed: snd_pcm_sync_stop(), constraint refinement and do_free_pages() all happen in between. snd_pcm_mmap_data(), on the other hand, takes no lock at all: it validates against the old buffer's state and dma_bytes, remaps its pages into the VMA, and only then increments mmap_count. A concurrent mmap() can therefore slip in between the check and the free. remap_pfn_range() installs writable PTEs for the old buffer's pages without taking page references, and the subsequent do_free_pages() returns those pages to the page allocator while the VMA still maps them. This leaves a stale, writable mapping of freed pages: a page-level use-after-free that can be leveraged for local privilege escalation. Make snd_pcm_mmap_data() participate in the buffer-access scheme introduced for hw_params/hw_free: acquire runtime->buffer_accessing before validating and remapping, and release it afterwards. Buffer reallocation already fails with -EBUSY while accessors are active, and the mmap side now fails with -EBUSY while a reallocation is in progress, so the validate/remap sequence and the check/free sequence can no longer interleave. A reproducer that turns this race into a stale writable mapping of the freed DMA buffer pages is available on request. Reported-by: Kimi Security Team <bug-report@moonshot.ai> Fixes: 92ee3c60ec9f ("ALSA: pcm: Fix races among concurrent hw_params and hw_free calls") Signed-off-by: Yilin Zhang <yilinzhang@moonshot.ai> Link: https://patch.msgid.link/20260831045506.889070-1-yilinzhang@moonshot.ai Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-31ALSA: pcm: Fix race between non-atomic ops and trigger-startTakashi Iwai1-0/+2
We protect the races of the concurrent state transitions between atomic PCM ops, but the checks between the non-atomic ops (hw_params, hw_free and prepare) and the atomic ops aren't perfect; there is a check of the conflicting PCM state at the beginning of hw_params & co, but the atomic PCM ops can be still issued during the non-atomic PCM operations. An example such scenario is that a thread A re-issues the PREPARE or HW_PARAMS for the already prepared stream, while another thread B triggers the PCM start in the middle of the prepare operation. Although this usually doesn't lead to much serious issues, it can give some inconsistency as reported by syzkaller (such as ODEBUG warning). There are various atomic PCM ops, and basically the only problem is the PCM start as it operates from the PREPARED state. Other trigger commands (stop, etc) are for the running or the other special state, hence they are filtered as pre-condition. This patch is for preventing the PCM trigger-start during the non- atomic operations in order to address the problems above. Fortunately, the hw_params, hw_free and prepare operations call snd_pcm_buffer_access_lock(), and this can be used for checking the concurrent operations at the PCM trigger -- which sets the runtime->buffer_accessing to a negative (if possible), so the PCM trigger just needs to check the runtime->buffer_accessing value; if it's negative, it means the concurrent non-atomic PCM ops is running. Reported-by: syzbot+225231fce6755d40d078@syzkaller.appspotmail.com Closes: https://lore.kernel.org/6a8f0de8.1d9ded08.62e62.00b5.GAE@google.com Cc: <stable@vger.kernel.org> Link: https://patch.msgid.link/20260828115542.3999-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-28Merge tag 'sound-fix-7.3-rc1' of ↵Linus Torvalds3-5/+11
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound Pull sound fixes from Takashi Iwai: "A collection of various small fixes since the last PR. Most changes are device-specific fixes, while there are a few fixes addressing the issues reported recently by fuzzers. Here are highlights: ALSA Core: - Prevent adding invalid kcontrols to the LED layer - Workaround for a false-positive mutex lockdep warning in rawmidi USB-audio: - Relaxed the sticky mixer behavior check that caused regressions - Fix an OOB write in Novation MIDI output - Proper cleanup after system-resume errors - Quirk updates for M-Audio Venom, Audient iD14 MkI, Logitech PRO X Wireless, SMSL USB DAC, and Creative Sound Blaster Play! 3 HD-audio: - Conexant headset plugin fixes - Quirk additions and fixes for HP Laptop 15, Lenovo IdeaPad Slim 3, TongFang XxAF5xxx, Lenovo Legion Pro 7, and Lenovo Yoga Pro 9 ASoC: - DAPM: Fix off-by-one check on the second enum channel - Tegra: Fix and sort register defaults - AMD quirk updates for ASUS FA401EA, HP OmniBook X Flip 16, HVY-WXX9/M1060, Alienware m18 R1, and MSI Thin A15 B7UC - Fixes Qualcomm TDM handling - Fix double put_device() on SoundWire - Codec fixes for rt766, tac5xx2, rt712, tas2783, and max98926 Misc: - Fix card leak on probe error on ice1712 driver - Hardening for legacy aoa, mtpav and pcxhr drivers" * tag 'sound-fix-7.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: (53 commits) ALSA: control: Don't add invalid kcontrols to LED layer ASoC: amd: acp-config: change quirks to cover all ASUS FA401EA variants ALSA: hda/conexant: Always enable the headset-mic pin on plugin ASoC: dapm: Fix off-by-one check on the second enum channel ASoC: amd: acp-config: force SoundWire probe on HP OmniBook X Flip 16 ASoC: amd: acp3x-es83xx: Add HVY-WXX9/M1060 DMI quirk ASoC: amd: acp-config: Add HVY-WXX9/M1060 DMI quirk ASoC: soc-generic-dmaengine: Fix DMA channel request warning ALSA: rawmidi: Another workaround for false-positive mutex lockdep warning ASoC: amd: yc: Add DMI entry for Alienware m18 R1 AMD ASoC: amd: yc: Add DMI entry for MSI Thin A15 B7UC ALSA: hda/realtek: Fix speaker mute LED for HP Laptop 15-fd0039nt ALSA: usb-audio: Complete cleanup after system-resume errors ALSA: hda/realtek: Add quirk for Lenovo IdeaPad Slim 3 15ABR8 ALSA: aoa: i2sbus: Check IRQ before requesting it ALSA: usb-audio: Skip mixer creation on M-Audio Venom ALSA: usb-audio: Skip reading sample rate on M-Audio Venom ASoC: rt766: add RT766/RT767 VA1 device IDs ALSA: hda/realtek: Add quirk for TongFang XxAF5xxx ALSA: usb-audio: fix OOB write in snd_usbmidi_novation_output() ...
2026-08-27ALSA: control: Don't add invalid kcontrols to LED layerTakashi Iwai1-0/+2
The kcontrol LED state layer tries to track the all associated kcontrol elements with naive assumptions that they are readable. But one can create a write-only element that has no get callback (even a user element can do it), and this may lead to a NULL dereference at the call chain of snd_ctl_led_notify(), as found by syzkaller. For avoiding the Oops, add a sanity check of the kcontrol's info and get callbacks, and just skip the invalid kcontrols before assigning the kctl to the LED layer. Reported-by: syzbot+b7fe2760ea6f1ee44b4d@syzkaller.appspotmail.com Closes: https://lore.kernel.org/6a9007b3.1d9ded08.62e62.00cd.GAE@google.com Fixes: 22d8de62f11b ("ALSA: control - add generic LED trigger module as the new control layer") Reviewed-by: Jaroslav Kysela <perex@perex.cz> Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260827113951.893291-1-tiwai@suse.de
2026-08-25ALSA: rawmidi: Another workaround for false-positive mutex lockdep warningTakashi Iwai2-5/+9
While we attempted to work around the false-positive lockdep warning due to the nested mutex lock in rawmidi at the open path for a UMP legacy rawmidi, it didn't cover the similar locking at its close path, and this still caused another false-positive reports by syzkaller. Add a similar workaround to snd_rawmidi_kernel_release() as done in the former commit 9c04742e73b3 ("ALSA: rawmidi: Work around false-positive mutex lockdep warning") to cover completely. Reported-by: syzbot+7d1edf0ff6a05961020c@syzkaller.appspotmail.com Closes: https://lore.kernel.org/6a8c7e4d.4d75e56a.c9a88.0052.GAE@google.com Link: https://patch.msgid.link/20260825134942.1289272-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-20Merge tag 'mm-stable-2026-08-18-18-39' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull MM updates from Andrew Morton: - "mm: drop "sub" prefix from various places" (Dev Jain) page->folio conversion and a naming cleanup - "mm/kasan: remove redundant initialization for kasan_flag_write_only" (Igor Putko) KASAN cleanup work - "mm/filemap: reduce unnecessary xarray lookups" (Chi Zhiling) Small speedup in the pagecaache read code - "mm/percpu: Fix possible NOFS/NOIO reclaim recursion" (Kaitao Cheng) Improve the vmalloc code - mainly the avoidance of GFP_KERNEL allocations when the caller asked for GFP_NOFS or GFP_NOIO - "mm/kmemleak: avoid soft lockup when scanning task stacks" (Breno Leitao) Avoid a soft lockup watchdog trigger from the kmemleak scanning code in extreme situations - "mm/page_owner: misc cleanups" (Ye Liu) Cleanups to the page_owner code. For some reason lots of people have been working on the page_owner code this cycle. - "mm: convert to walk_page_range_vma() to eliminate find_vma()" (Kefeng Wang) Simplify and accelerate the page walking library function - "mm/migrate: preparatory cleanups for batch copy and offload" (Shivank Garg) Cleanups in the migration code - "mm/page_owner: add per-fd filter infrastructure for print_mode and NUMA filtering" (Zhen Ni) Per-fd filtering to page_owner in order to reduce the sometimes vast amount of output it can produce - "mm: Refactor bootmem gigantic hugepage allocation" (Muchun Song) Fixes and preparatory cleanups around bootmem HugeTLB handling, sparse initialization ordering, and related vmemmap setup - "mm/zsmalloc: reduce lock contention in zs_free()" (Wenchao Hao) Reduce lock contention in zs_free(), which dominates the unmap path under memory pressure on Android (LMK kills) and on x86 servers running zswap-heavy workloads. Up to 1.83x improvement in microbenchmarking. - "move alloc_tag.c file under mm/" (Suren Baghdasaryan) - "samples/damon: handle damon_{start,stop}() failures" (SJ Park) Fix improper handling of damon_start(), damon_stop(), and damon_call() failures across DAMON sample modules to prevent potential memory leaks, operation disruptions and use-after-free bugs - "mm/damon/sysfs: kobject_del() directories that users can create/remove" (SJ Park) Fix delayed sysfs directory removal under DEBUG_KOBJECT_RELEASE causeing creation failures due to duplicate directory names by adding missing kobject_del() calls before creating new directories - "mm: cleanup clear_not_present_full_ptes()" (David Hildenbrand) Clean up the core pte handling code - "selftests/damon: misc fixes for test bugs" (Kunwu Chan) Fix several bugs in the DAMON selftests - "selftests/damon: fix memcg_path staging handling" (Cheng Nie) Fix a bug in _damon_sysfs.py for damos_filter memcg_path setup, and add a test case for it in sysfs.py. - "selftests/damon: test kdamond refresh_ms" (Ruslan Valiyev) Selftest coverage for DAMON's refresh_ms sysfs feature by updating the test control module and verifying that scheme stats update automatically without manual intervention - "mm/damon: five misc fixups" (Akinobu Mita) Miscellaneous DAMON fixups. - "mm/damon/core: detect internal variation above max_nr_regions/2" (Jiayuan Chen) Fix DAMON's region splitting behavior when region counts exceed half the maximum budget by dynamically scaling down the split fraction as the limit approaches, preventing large regions from staying un-split, and add corresponding KUnit test coverage - "mm: preparatory patches for PMD level swap entries" (Usama Arif) Refactor and clean up PMD softleaf helpers, call sites, and architecture flags to lay the groundwork for a follow-up series that introduces PMD page table swap entries - "mm/damon: update, optimize, and clean up doc, tests, and code" (SJ Park) Update DAMON design and ABI documentation, expands unit and selftest coverage, optimize damon_commit_target_regions(), and clean up recently added sysfs interface code for better readability - "mm/vmpressure: reduce CPU, memory and code overhead on cgroup v2" (Usama Arif) Optimize vmpressure() by skipping unnecessary work on cgroup v2 for userspace event notifications and refactor v1-only eventfd handling into mm/memcontrol-v1.c to reduce memory overhead and code complexity - "selftests/mm: refactor pkey helpers and fix mmap error handling" (Hongfu Li) Refactor pkeys shared tracing and assertion helpers into a common file, unify protection key selftests to use consistent diagnostic logging and assertions, and enforce standardized MAP_FAILED return checks for mmap() calls across the tests - "mm/damon: optimize out nr_accesses_bp" (SJ Park) Replace the error-prone, continuously updated nr_accesses_bp field in damon_region with an on-demand moving sum function, reducing structure memory overhead and avoiding state corruption bugs - "Open HugeTLB allocation routine for more generic use" (Ackerley Tng) Decouple HugeTLB folio allocation from VMA dependencies by introducing hugetlb_alloc_folio(), enabling subsystems like guest_memfd to allocate HugeTLB folios without standard VMA reservations or pseudo-VMAs - "mm/damon: provide pseudo moving sum probe_hits" (SJ Park) Integrate DAMON's probe_hits attribute counter into the pseudo moving sum infrastructure, enabling real-time, online monitoring without waiting for full aggregation intervals - "mm: Some cleanups for page allocator APIs" (Brendan Jackman) Simplify and refactor the page allocator entry points and flags by unifying allocation paths, adding internal alloc_flags arguments, and eliminating redundant __ prefixed alloc_pages variants. - "Fix incorrect access of hugetlb pte entries" (Dev Jain) Enforce the consistent use of huge_ptep_get() instead of ptep_get() for HugeTLB entries and fixes an unaligned address issue in arm64's huge_ptep_get() implementation - "mm/damon: validate all parameters in the core" (SJ Park) Consolidate parameter validation into the DAMON core specifically within damon_start() and damon_commit_ctx() to centralize error checking, eliminate caller-side redundant checks and to improve maintenance efficiency - "tools/mm/page_owner_sort: fix filtering and cleanup issues" (Yichong Chen) Rename is_need() to filter_record() for clearer return semantics, fix per-record allocation memory leaks and bound output copies in search_pattern() to address an existing buffer issue - "memcg: bail out reclaim when memcg is dying" (Jiayuan Chen) Mitigate a system-wide stall which occurs when a cgroup is removed while one of its memory control files is doing synchronous reclaim - "mm/memory-failure: add panic option for unrecoverable pages" (Breno Leitao) Introduce an opt-in vm.panic_on_unrecoverable_memory_failure sysctl that immediately panics the kernel on unrecoverable memory errors in kernel-owned pages to preserve error context and prevent delayed, silent data corruption - "mm/damon: refactor damon_{start,stop,commit}() for simple error handling" (SJ Park) Refactor the DAMON core API functions to guarantee that all contexts are fully stopped when damon_start(), damon_stop(), or damon_commit() fail, eliminating the need for complex and error-prone caller-side cleanup code - "Keep tail page private zero at free and folio split" (Zi Yan) Add checks to ensure tail_page->private is zero when freeing compound or high-order pages and when promoting tail pages during large folio splits. By validating these fields at free and split time, it allows the removal of redundant private field clearing inside prep_compound_tail() - "mm: drop redundant lru_add_drain in anon folio reuse paths" (Barry Song) Eliminate redundant lru_add_drain() calls in wp_can_reuse_anon_folio() and do_swap_page() to reduce LRU lock contention and system overhead By validating folio refcounts against the LRU cache before draining and removing unnecessary drains in the swap path, it achieves up to a 30.5% reduction in drain calls during heavy swap workloads - "mm: clean up folio LRU and swap declarations" (Jianyue Wu) Reorganize folio LRU and swap code by relocating page-cluster state to mm/swap_state.c, renaming mm/swap.c to mm/folio.c, and moving MM-internal reclaim declarations into mm/internal.h. - "userfaultfd: working set tracking for VM guest memory" (Kiryl Shutsemau) Add userfaultfd support for tracking the working set of VM guest memory, so a VMM can identify hot pages and reclaim cold ones to tiered or remote storage - "mm: remove CONFIG_HAVE_BOOTMEM_INFO_NODE (Part 2)" (David Hildenbrand) Remove the remaining pieces of CONFIG_HAVE_BOOTMEM_INFO_NODE, performing some smaller cleanups around freeing of reserved vmemmap pages on the way. - "mm/damon: update probe hits for runtime parameter commits" (SJ Park) Ensure that DAMON's probe_hits attribute counter is properly updated when monitoring intervals are changed at runtime, matching the behavior of nr_accesses. To achieve this, it refactors and renames existing helper functions for shared use, applies the updates to probe_hits, and handles edge cases in damon_probe_hits_mvsum() to maintain measurement accuracy. - "KSM: performance optimizations for rmap_walk_ksm" (xu xin) Resolve a severe KSM reverse-mapping performance bottleneck where thousands of split VMAs sharing a single anon_vma cause extended lock contention. By adding an interval-filtering check during the rmap walk, it reduces worst-case anon_vma lock hold times from over 500ms down to under 2ms, preventing application freezes and latency spikes under memory pressure. - "mm: split a couple of headers from internal.h" (Mike Rapoport) Split declarations related to mm_init, memblock, vmalloc and sparse into new headers - "KSM: use linear_page_index in collect_procs_ksm()" (xu xin) Apply the interval tree optimization from rmap_walk_ksm() to collect_procs_ksm() to avoid iterating over non-matching VMAs during KSM memory error handling. It hoists loop-invariant address initialization and restricts the anon_vma_interval_tree_foreach walk to a targeted page offset range, reducing redundant checks and improving lookup efficiency. - "selftests/mm: avoid false failures in hugetlb and KSM tests" (Sayali Patil) Fix issues in the hugetlb and KSM MM selftest categories that can report failures when the prerequisites for the tests are not satisfied - "mm/damon: introduce data attributes only monitoring" (SJ Park) Introduce attribute-weighted region management in DAMON, allowing users to prioritize specific data attributes (such as page sizes or cgroups) over or instead of access monitoring. By assigning weights to attribute probes, DAMON can completely disable access tracking and adjust monitoring regions based on weighted probe-hit counters to optimize monitoring quality for attribute-focused workloads. - "mm/hmm: Add mmap lock-drop support for userfaultfd-backed mappings" (Stanislav Kinsburskii) Extend hmm_range_fault() to support userfaultfd-backed regions by allowing the mmap lock to be dropped during fault handling via a new hmm_range_fault_locked() helper. By accepting a locked pointer and signaling retry status when lock release occurs, it enables page fault resolution in userfaultfd regions while preserving backward compatibility for existing callers. - "mm: make VMA page offset handling more consistent" (Lorenzo Stoakes) Clean up and standardize how vma->vm_pgoff is accessed and manipulated across file-backed and anonymous mappings in the kernel It introduces dedicated helper functions such as vma_start_pgoff(), vma_end_pgoff(), vma_set_pgoff() and linear_page_delta() while renaming rmap interval tree helpers to better reflect their functionality. These changes establish a cleaner foundation for future work that will unify virtual page offset indexing for all anonymous and CoW'd folios. - "mm: handle device-private PMDs in walk callbacks" (Usama Arif) Address kernel panics and state corruption caused by MM walk callbacks reaching non-present device-private PMD swap entries created during HMM migrations It ensures that functions which acquire pmd_trans_huge_lock() properly recognize device-private PMDs instead of assuming a present THP or a standard migration entry. - "mm/rmap: Refactor try_to_unmap_one" (Dev Jain) Refactor try_to_unmap_one by modularizing Hugetlb, anonymous-lazyfree, and anonymous-swapbacked logic into dedicated functions, laying the structural groundwork for batched anonymous large folio unmapping. - "Docs/ABI/damon: sysfs ABI document fixes and additions" (Song Hu) Fix typos and fills in missing entries in the DAMON sysfs ABI document - "dax/kmem: atomic whole-device hotplug via sysfs" (Gregory Price) Introduce an atomic sysfs state attribute and supporting DAX/MM infrastructure to prevent userland races when offlining and removing entire memory regions By adding an unplugged state alongside standard online modes, it enables whole-device atomic hotplug control while preserving backward compatibility. - "mm: convert more vm_flags_t users to vma_flags_t" (Lorenzo Stoakes) Continue transitioning the kernel from the deprecated vm_flags_t type to vma_flags_t across core memory management infrastructure. It replaces legacy type usage in core functions such as do_mmap(), unmapped area allocation, mm->def_vma_flags, and VMA operations like mlock, mprotect, and mremap. - "Two small patches to clean up mm/mm_slot.h" (xu xin) Refactor mm_slot.h by introducing mm_slot_remove() to unify duplicate slot deletion sequences in khugepaged and KSM. It also adds code documentation explaining why mm_slot_lookup and mm_slot_insert must remain as preprocessor macros rather than static inline functions. - "mm/damon/core: hide core-private struct fields" (SJ Park) Clean up DAMON core structures by consistently marking internal-only fields with private: comment tags to prevent improper direct access from outer layers. It enforces encapsulation across core structures including damon_region, damon_target, and damon_ctx and updates DAMON_SYSFS to interact through approved access APIs instead of exposing raw struct members. - "mm/damon: unurgent fixes for infinite loop, NULL de-ref and races" (SJ Park) Address potential infinite loops, NULL dereferences, and race conditions identified in DAMON It fixes an infinite loop triggered by extreme user configurations, a NULL pointer dereference within unit tests and minor monitoring accuracy degradation caused by subtle runtime races. - "mm/page_alloc: fixes for free_pages_nolock() on RT/UP" (Brendan Jackman) Fix an NMI safety flaw in __free_frozen_pages() where freeing pages on non-SMP or PREEMPT_RT kernels can bypass can_spin_trylock() checks via non-PCP or isolated migration paths. It also resolves potential kernel crashes and privilege escalation risks triggered when BPF tracing runs in NMI context alongside memory hotplug or large allocation frees. - "mm/page_alloc: couple of followups for recent cleanups" (Brendan Jackman) Clean up and update page allocator nomenclature, documentation, and debug assertions. It aligns internal FPI_ flags with the public "nolock" naming convention, removes outdated internal implementation details from high-level page allocator comments, and eliminates obsolete VM_BUG_ON() assertions in allocation paths. - "mm/mseal: further cleanups" (Lorenzo Stoakes) Refactor and simplify the mseal implementation by clarifying API boundaries and removing unnecessary code complexity. It replaces generic do_mseal() usage outside the syscall with a dedicated mseal_mmap_page_zero() helper for MMAP_PAGE_ZERO, eliminates mm_struct parameters to enforce that sealing applies only to current->mm, and streamlines overall logic and comments with no functional changes intended. - "mm/vmscan: fix swappiness=max and clean up per-node proactive reclaim" (Ridong Chen) Resolve reclaim behavior bugs and clean up function parameters across memory reclaim paths It fixes swappiness=max in both standard reclaim and MGLRU so unswappable anonymous memory no longer falls back to evicting page cache, ensures reclaim_store() returns accurate error codes instead of collapsing all failures into -EAGAIN, and removes the obsolete gfp_mask parameter from __node_reclaim(). - "mm: mincore: misc cleanups" (Kefeng Wang) Clean up and simplifies the mincore code. Most importantly, it removes the historical special behavior that always reports VM_PFNMAP pages as non-resident. - "mm/huge_memory: drop dead split helper variants" (Kiryl Shutsemau) Two trivial cleanups in the folio split API - "mm/damon: fix uninitialized DAMOS field and kunit exec expectation bugs" (SJ Park) Resolve minor operational and testing bugs in DAMON identified by Sashiko. It initializes the damos->last_applied field to prevent occasional efficiency degradation and fixes invalid memory accesses in DAMON KUnit tests during test failure handling. - "cleanup for stable_page_flags()" (Jinjiang Tu) Clean up and refactor stable_page_flags() used by /proc/kpageflags without altering functionality. It uses BIT_ULL() to prevent shift-overflow warnings on 64-bit flag bits, converts folio-specific flag checks to standard folio_test_*() helpers, and removes redundant CONFIG_PAGE_IDLE_FLAG handling. - "Batch unmap of uffd-wp file folios" (Dev Jain) Extend batched folio unmapping support to file folios within userfaultfd write-protect (uffd-wp) VMAs by adding batching capabilities to pte_install_uffd_wp_if_needed(). This removes special-case restrictions on uffd-wp VMAs in try_to_unmap_one(), significantly simplifying the function's control flow and complexity. - "mm/early_ioremap: clarify and clean up early_ioremap_reset()" (Sang-Heon Jeon) Clarify and clean up the architecture-specific usage of __late_set_fixmap() and __late_clear_fixmap() after early_ioremap_reset() It adds explicit documentation regarding when early_ioremap_reset() must be called and removes redundant macro definitions and reset calls in the RISC-V and ARM64 architectures. - "mm: fix reclaim storms in defrag_mode" (Johannes Weiner) Address severe performance regressions, swap storms, and spurious OOMs caused by vm.defrag_mode=1 under high memory pressure in Meta production It updates the page allocator slowpath so non-movable allocation requests actively trigger direct reclaim and direct compaction at pageblock_order scale, allowing them to claim whole pageblocks rather than spinning unproductively. - "zram: lockmap tweaks" (Sebastian Siewior) Optimize and fix lockdep tracking for zram devices by consolidating per-entry lockmaps and isolate lock classes across multiple instances This reduces memory overhead by replacing per-entry lockdep_map instances with a single map per struct zram, and assigns a dynamic lock_class_key to each instance to prevent false deadlock reports when different zram devices are backed by distinct filesystems. * tag 'mm-stable-2026-08-18-18-39' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (501 commits) selftests/mm: thuge-gen: fix test_shmget() for PAGE_SIZE check selftests/mm: unpoison pages in memory-failure teardown mm/shmem: downgrade final i_blocks check in shmem_evict_inode() to pr_warn() mm/khugepaged: replace mutex_lock/mutex_unlock usage with guard macro mm/zsmalloc: fix release order of locks in zs_page_migrate() Documentation: zram: remove sections numbering ksm: stop iterating VMAs when ksm_test_exit returns true mm: fold userfaultfd_rwp() to false without CONFIG_ARCH_HAS_PTE_PROTNONE mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch() zram: use a custom key for each zram object zram: move lockmap to be per-zram instead per table selftests/mm: fix gup_longterm EINVAL error message mm: page_alloc: fix non-movable reclaim storm in defrag_mode mm: page_alloc: move capture_control to the page allocator mm: compaction: support non-movable compaction for pageblock requests mm: page_alloc: __GFP_FS lockdep annotation for direct compaction hugetlb: evaluate subpool free state while locked mm/damon: remove trailing semicolons after function definitions mm/damon/ops-common: prevent migration fallback to non-target nodes mm/damon: update outdated comment about DAMOS filter handling ...
2026-08-14ALSA: core: Fix use-after-free in snd_card_do_free()Aleksandr Nogikh1-1/+3
A use-after-free was detected in snd_card_do_free() when a sound card managed by devres is unbound while a user-space application still holds an open file descriptor. For managed cards, the memory is allocated using devres_alloc(), and its release function is set to __snd_card_release(), which calls snd_card_free(). When the device is unbound, the unbind thread calls snd_card_free(), which drops a reference to the card's device. If the user thread still has an open file descriptor, the reference count does not reach zero, and the unbind thread blocks on wait_for_completion(&released). When the user thread closes the file descriptor, it drops the final reference, invoking the device release callback release_card_device(), which calls snd_card_do_free(). snd_card_do_free() performs cleanup and calls complete(card->release_completion). This wakes up the unbind thread, which returns from snd_card_free() and __snd_card_release(). The devres core then immediately frees the memory block containing the snd_card structure. Meanwhile, the user thread continues execution in snd_card_do_free() and evaluates `if (!card->managed)`. It reads the `managed` boolean from the snd_card structure that was just freed by the unbind thread, triggering a KASAN use-after-free. Fix this by caching the value of card->managed in a local variable before calling complete(). This ensures that the card pointer is not dereferenced after the unbind thread has been woken up and potentially freed the card. BUG: KASAN: use-after-free in snd_card_do_free sound/core/init.c:604 [inline] BUG: KASAN: use-after-free in release_card_device+0x1ab/0x1b0 sound/core/init.c:153 Read of size 1 at addr ffff8881912ec909 by task syz-executor130/5857 Call Trace: <TASK> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description+0x55/0x1e0 mm/kasan/report.c:378 print_report+0x58/0x70 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 snd_card_do_free sound/core/init.c:604 [inline] release_card_device+0x1ab/0x1b0 sound/core/init.c:153 device_release+0xc4/0x1f0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x222/0x550 lib/kobject.c:737 snd_card_file_remove+0x331/0x390 sound/core/init.c:1125 snd_pcm_release+0x12c/0x160 sound/core/pcm_native.c:2986 __fput+0x418/0xa50 fs/file_table.c:512 fput_close_sync+0x11f/0x240 fs/file_table.c:617 __do_sys_close fs/open.c:1511 [inline] __se_sys_close fs/open.c:1496 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1496 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> Fixes: e8ad415b7a55 ("ALSA: core: Add managed card creation") Assisted-by: Gemini:gemini-3.6-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: syzbot+7061d72c26b7daebe2b4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7061d72c26b7daebe2b4 Link: https://syzkaller.appspot.com/ai_job?id=24752a23-f0b6-49c1-bf20-4fa89c2e7eb2 Signed-off-by: Aleksandr Nogikh <nogikh@google.com> Link: https://patch.msgid.link/02042186-27b7-42a9-b64e-f93ce8fbe05a@mail.kernel.org Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-13ALSA: seq: midi: Serialize input teardown with event_inputJohn Keeping1-6/+31
snd_midi_input_event() must not be running while a rawmidi substream is closing, since this can lead to the trigger state becoming out-of-step through this sequence in snd_rawmidi_input_trigger(): snd_rawmidi_input_trigger(up=0) snd_midi_input_event() -> snd_rawmidi_kernel_read() -> snd_rawmidi_input_trigger(up=1) -> cancel_work_sync() which ends with the underlying device being active unexpectedly. When this is called from close_substream(), further input can re-trigger the input event leaving it running after rawmidi_release_priv() has set rfile->rmidi to NULL which leads to: Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b0 Call trace: snd_midi_input_event+0x3c/0x134 [snd_seq_midi] (P) snd_rawmidi_input_event_work+0x1c/0x2c process_one_work+0x150/0x3a4 worker_thread+0x190/0x318 Apply a similar approach to commit ef7607ab1c8ad ("ALSA: seq: midi: Serialize output teardown with event_input") which fixed the same issue in the output direction, but updated to use RCU following Takashi Iwai's proposed follow-on patch [1]. With this change in place, midisynth_unsubscribe() clears the input file so snd_midi_input_event() will not re-trigger the stream and will be quiesced by the cancel_work_sync() in snd_rawmidi_input_trigger(). [1] https://lore.kernel.org/linux-sound/20260813144224.753399-1-tiwai@suse.de/ Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: John Keeping <jkeeping@inmusicbrands.com> Link: https://patch.msgid.link/20260813150810.795393-1-jkeeping@inmusicbrands.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-13ALSA: seq: midi: Optimize event_input locking with RCUTakashi Iwai1-13/+11
The recent fix for serializing the output teardown introduced a spinlock invocation at every MIDI output event via event_process_midi. Since this is a hot path, let's do performance optimization with RCU. The new output_substream __rcu pointer is published via rcu_assign_pointer() in midisynth_use() after output_rfile is set, and cleared in midisynth_unuse() before the resource teardown. event_process_midi() reads it under rcu_read_lock() and bumps output_use_lock inside that section, which is necessary to close the window between the pointer dereference and the refcount increment. midisynth_unuse() calls synchronize_rcu() before snd_use_lock_sync(): this guarantees that any reader who obtained a non-NULL pointer has already called atomic_inc (output_use_lock), so the subsequent snd_use_lock_sync() sees the correct in-flight count. Fixes: ef7607ab1c8a ("ALSA: seq: midi: Serialize output teardown with event_input") Link: https://patch.msgid.link/20260813144224.753399-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-13ALSA: kunit: Drop __force castsTakashi Iwai1-2/+2
Now that the bitwise parameter definitions are gone for PCM parameters, we don't have to cast with ugly __force prefix. Simply drop those superfluous casts Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260812060557.80445-7-tiwai@suse.de
2026-08-13ALSA: oss: Drop __force castsTakashi Iwai2-18/+18
Now that the bitwise parameter definitions are gone for PCM parameters, we don't have to cast with ugly __force prefix. Simply drop those superfluous casts. Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260812060557.80445-6-tiwai@suse.de
2026-08-13ALSA: control: Drop __force castsTakashi Iwai1-6/+6
Now that the bitwise parameter definitions are gone for control parameters, we don't have to cast with ugly __force prefix. Simply drop those superfluous casts. Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260812060557.80445-5-tiwai@suse.de
2026-08-13ALSA: pcm: Drop __force castsTakashi Iwai3-35/+30
Now that the bitwise parameter definitions are gone for PCM parameters, we don't have to cast with ugly __force prefix. Simply drop those superfluous casts. Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260812060557.80445-3-tiwai@suse.de
2026-08-12ALSA: seq: Drop the dead struct snd_seq_event_bounceHyeongJun An1-3/+2
The struct describes a bounce payload of an error code followed by the original event and its external data. No kernel has ever sent that. Before commit efc86691e4d8 ("ALSA: seq: Fix kernel heap address leak in bounce_error_event()") the kernel emitted no SNDRV_SEQ_EVENT_BOUNCE at all, and since then it sends the event record alone. Nothing has ever read it either. Its only accessor, snd_seq_event_bounce_ext_data(), has had no caller for the whole git history, and it did not even compile until commit c7e0b5bf9fff ("[ALSA] Remove xxx_t typedefs: Sequencer") incidentally repaired the type name it referred to, three years after the git import. Drop the accessor along with the struct. This removes a definition from a UAPI header. Since no kernel ever produced the layout, nothing can have parsed it, but a program that merely names the type will need to stop. Suggested-by: Takashi Iwai <tiwai@suse.de> Assisted-by: Claude:claude-opus-5 Signed-off-by: HyeongJun An <sammiee5311@gmail.com> Link: https://patch.msgid.link/20260812141506.4016387-1-sammiee5311@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-11ALSA: seq: Don't leak the extension cell pointer in the bounce payloadHyeongJun An1-6/+10
The bounce_error_event() embeds the failed event in the bounce payload by pointing data.ext.ptr at it. When that event is a queued variable-length event, its own data.ext.ptr holds the address of its first extension cell, put there by snd_seq_event_dup(). The payload goes out verbatim through snd_seq_expand_var_event(), so the address reaches userspace. That is the same address commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read") removed from the event header. The read path still clears it there, just above the call that expands the payload. Embed a sanitised copy instead, treated exactly as snd_seq_read() treats the header. A stack copy is enough because delivery is synchronous and snd_seq_event_dup() copies before returning. An unprivileged client reaches this by setting SNDRV_SEQ_FILTER_BOUNCE, queueing a variable-length event to a port that does not exist and reading the bounce back. Eight bytes on 64-bit, from its own pool. Fixes: efc86691e4d8 ("ALSA: seq: Fix kernel heap address leak in bounce_error_event()") Assisted-by: Claude:claude-opus-5 Signed-off-by: HyeongJun An <sammiee5311@gmail.com> Link: https://patch.msgid.link/20260811131835.3837024-1-sammiee5311@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
2026-08-10ALSA: seq: Use RCU for the UMP client output substreamTakashi Iwai1-16/+22
The UMP sequencer client protects its output rawmidi file (out_rfile) with an rwlock (output_lock). seq_ump_process_event(), the port's event_input callback, reads out_rfile.output under read_lock on every delivered UMP event, while the open/close paths (serialized by ump->open_mutex) publish and clear out_rfile under write_lock. Output is opened/closed only on the subscribe/use lifecycle while delivery happens per event, so this is another read-mostly hot path. Convert it to RCU and drop the rwlock. out_rfile is an embedded struct rather than a pointer, so instead of restructuring it, add an RCU-protected shadow of the substream (out_substream) for the reader; out_rfile itself becomes writer-only state accessed solely under open_mutex. The reader now runs lock-free under rcu_read_lock() via rcu_dereference(), and open publishes the substream with rcu_assign_pointer(). On close the substream is cleared with rcu_assign_pointer(NULL) and the rawmidi is released only after synchronize_rcu(), so no reader in the delivery path can still be writing to the substream when snd_rawmidi_kernel_release() runs. Dropping write_lock_irqsave() from the writers is safe: they run in process context under open_mutex, and the sole atomic reader now uses RCU, which is IRQ-safe. Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260810133711.42483-6-tiwai@suse.de
2026-08-10ALSA: seq: Use RCU for the virmidi file listTakashi Iwai1-8/+11
Each virmidi device keeps a list of its opened input files (filelist) protected by both an rwlock (filelist_lock) and a rw_semaphore (filelist_sem). snd_virmidi_dev_receive_event() walks the list on the sequencer event input path -- read_lock() when the event is delivered in atomic context, down_read() otherwise -- decoding each incoming event into the file's rawmidi buffer. The writers (input open/close) take both locks to add/remove entries. This is another typical dual-lock read-mostly pattern as the port subscriber list: files are opened/closed rarely while the receive callback runs per event. Let's convert the traversal to RCU and drop the rwlock; the existing filelist_sem keeps serializing the writers. The atomic input path now runs lock-free under rcu_read_lock(), and both readers share a single list_for_each_entry_rcu() (valid under the rwsem via lockdep_is_held()). The writers switch to list_add_tail_rcu() / list_del_rcu(). snd_virmidi_input_close() freed the entry (parser and struct) immediately after list_del. A concurrent lockless reader in the atomic path may still be dereferencing it, so the close path now waits for an RCU grace period after list_del_rcu() before freeing; synchronize_rcu() is used rather than kfree_rcu() because the parser must also be released after the grace period, not just the struct. Non-atomic readers are already excluded by the down_write, so only the atomic RCU readers need the grace period. Dropping write_lock_irq() from the writers is safe: no writer runs in atomic/IRQ context, and the sole atomic reader now uses RCU, which is IRQ-safe. Signed-off-by: Takashi Iwai <tiwai@suse.de> Link: https://patch.msgid.link/20260810133711.42483-5-tiwai@suse.de
2026-08-10ALSA: seq: Use RCU for the client tableTakashi Iwai1-13/+30
The sequencer keeps a global table of clients (clienttab[]) indexed by client id, protected by the global clients_lock spinlock. The lookup snd_seq_client_use_ptr() reads a slot and takes a use_lock reference on the client, and this runs on the event delivery hot path: every dispatched event resolves its destination (and often source) client through it. The spinlock's only job on the read side is to make the "pointer is non-NULL" test and the reference increment indivisible with respect to the writer that nulls the slot and then drains the refcount. Clients come and go rarely but delivery happens constantly, so this is yet another read-mostly case as the port and subscriber lists. Convert the table to RCU: the read side now runs lock-free under rcu_read_lock() and takes the use_lock reference via rcu_dereference(), removing contention on the single global spinlock from the delivery path. The writers keep clients_lock (still needed to serialize slot allocation) and publish / unpublish via rcu_assign_pointer(); creation and destruction remain serialized at a higher level by register_mutex. As with the ports, the client is not freed via kfree_rcu(): its lifetime is governed by the use_lock refco