CVE-2024-57896 (GCVE-0-2024-57896)
Vulnerability from cvelistv5 – Published: 2025-01-15 13:05 – Updated: 2026-08-05 11:46
VLAI
EPSS
VEX
Title
btrfs: flush delalloc workers queue before stopping cleaner kthread during unmount
Summary
In the Linux kernel, the following vulnerability has been resolved:
btrfs: flush delalloc workers queue before stopping cleaner kthread during unmount
During the unmount path, at close_ctree(), we first stop the cleaner
kthread, using kthread_stop() which frees the associated task_struct, and
then stop and destroy all the work queues. However after we stopped the
cleaner we may still have a worker from the delalloc_workers queue running
inode.c:submit_compressed_extents(), which calls btrfs_add_delayed_iput(),
which in turn tries to wake up the cleaner kthread - which was already
destroyed before, resulting in a use-after-free on the task_struct.
Syzbot reported this with the following stack traces:
BUG: KASAN: slab-use-after-free in __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089
Read of size 8 at addr ffff8880259d2818 by task kworker/u8:3/52
CPU: 1 UID: 0 PID: 52 Comm: kworker/u8:3 Not tainted 6.13.0-rc1-syzkaller-00002-gcdd30ebb1b9f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: btrfs-delalloc btrfs_work_helper
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x169/0x550 mm/kasan/report.c:489
kasan_report+0x143/0x180 mm/kasan/report.c:602
__lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]
try_to_wake_up+0xc2/0x1470 kernel/sched/core.c:4205
submit_compressed_extents+0xdf/0x16e0 fs/btrfs/inode.c:1615
run_ordered_work fs/btrfs/async-thread.c:288 [inline]
btrfs_work_helper+0x96f/0xc40 fs/btrfs/async-thread.c:324
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
worker_thread+0x870/0xd30 kernel/workqueue.c:3391
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Allocated by task 2:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4104 [inline]
slab_alloc_node mm/slub.c:4153 [inline]
kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205
alloc_task_struct_node kernel/fork.c:180 [inline]
dup_task_struct+0x57/0x8c0 kernel/fork.c:1113
copy_process+0x5d1/0x3d50 kernel/fork.c:2225
kernel_clone+0x223/0x870 kernel/fork.c:2807
kernel_thread+0x1bc/0x240 kernel/fork.c:2869
create_kthread kernel/kthread.c:412 [inline]
kthreadd+0x60d/0x810 kernel/kthread.c:767
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Freed by task 24:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2338 [inline]
slab_free mm/slub.c:4598 [inline]
kmem_cache_free+0x195/0x410 mm/slub.c:4700
put_task_struct include/linux/sched/task.h:144 [inline]
delayed_put_task_struct+0x125/0x300 kernel/exit.c:227
rcu_do_batch kernel/rcu/tree.c:2567 [inline]
rcu_core+0xaaa/0x17a0 kernel/rcu/tree.c:2823
handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:554
run_ksoftirqd+0xca/0x130 kernel/softirq.c:943
---truncated---
Severity
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-02-11 15:40 UTC
CWE
- CWE-416 - Use After Free
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
fd340d0f68cc87badfc9efcb226f23a5428826a0 , < a2718ed1eb8c3611b63f8933c7e68c8821fe2808
(git)
Affected: fd340d0f68cc87badfc9efcb226f23a5428826a0 , < 63f4b594a688bf922e8691f0784679aa7af7988c (git) Affected: fd340d0f68cc87badfc9efcb226f23a5428826a0 , < 1ea629e7bb2fb40555e5e01a1b5095df31287017 (git) Affected: fd340d0f68cc87badfc9efcb226f23a5428826a0 , < 35916b2f96505a18dc7242a115611b718d9de725 (git) Affected: fd340d0f68cc87badfc9efcb226f23a5428826a0 , < d77a3a99b53d12c061c007cdc96df38825dee476 (git) Affected: fd340d0f68cc87badfc9efcb226f23a5428826a0 , < f10bef73fb355e3fc85e63a50386798be68ff486 (git) |
guessed | |
| Linux | Linux |
Affected:
5.0
Unaffected: 0 , < 5.0 (semver) Unaffected: 5.10.233 , ≤ 5.10.* (semver) Unaffected: 5.15.176 , ≤ 5.15.* (semver) Unaffected: 6.1.124 , ≤ 6.1.* (semver) Unaffected: 6.6.70 , ≤ 6.6.* (semver) Unaffected: 6.12.9 , ≤ 6.12.* (semver) Unaffected: 6.13 , ≤ * (original_commit_for_fix) |
guessed |
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: flush delalloc workers queue before stopping cleaner kthread during unmount\n\nDuring the unmount path, at close_ctree(), we first stop the cleaner\nkthread, using kthread_stop() which frees the associated task_struct, and\nthen stop and destroy all the work queues. However after we stopped the\ncleaner we may still have a worker from the delalloc_workers queue running\ninode.c:submit_compressed_extents(), which calls btrfs_add_delayed_iput(),\nwhich in turn tries to wake up the cleaner kthread - which was already\ndestroyed before, resulting in a use-after-free on the task_struct.\n\nSyzbot reported this with the following stack traces:\n\n BUG: KASAN: slab-use-after-free in __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089\n Read of size 8 at addr ffff8880259d2818 by task kworker/u8:3/52\n\n CPU: 1 UID: 0 PID: 52 Comm: kworker/u8:3 Not tainted 6.13.0-rc1-syzkaller-00002-gcdd30ebb1b9f #0\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\n Workqueue: btrfs-delalloc btrfs_work_helper\n Call Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0x169/0x550 mm/kasan/report.c:489\n kasan_report+0x143/0x180 mm/kasan/report.c:602\n __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089\n lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]\n _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162\n class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]\n try_to_wake_up+0xc2/0x1470 kernel/sched/core.c:4205\n submit_compressed_extents+0xdf/0x16e0 fs/btrfs/inode.c:1615\n run_ordered_work fs/btrfs/async-thread.c:288 [inline]\n btrfs_work_helper+0x96f/0xc40 fs/btrfs/async-thread.c:324\n process_one_work kernel/workqueue.c:3229 [inline]\n process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310\n worker_thread+0x870/0xd30 kernel/workqueue.c:3391\n kthread+0x2f0/0x390 kernel/kthread.c:389\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n \u003c/TASK\u003e\n\n Allocated by task 2:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x3f/0x80 mm/kasan/common.c:68\n unpoison_slab_object mm/kasan/common.c:319 [inline]\n __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345\n kasan_slab_alloc include/linux/kasan.h:250 [inline]\n slab_post_alloc_hook mm/slub.c:4104 [inline]\n slab_alloc_node mm/slub.c:4153 [inline]\n kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205\n alloc_task_struct_node kernel/fork.c:180 [inline]\n dup_task_struct+0x57/0x8c0 kernel/fork.c:1113\n copy_process+0x5d1/0x3d50 kernel/fork.c:2225\n kernel_clone+0x223/0x870 kernel/fork.c:2807\n kernel_thread+0x1bc/0x240 kernel/fork.c:2869\n create_kthread kernel/kthread.c:412 [inline]\n kthreadd+0x60d/0x810 kernel/kthread.c:767\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n\n Freed by task 24:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x3f/0x80 mm/kasan/common.c:68\n kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582\n poison_slab_object mm/kasan/common.c:247 [inline]\n __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264\n kasan_slab_free include/linux/kasan.h:233 [inline]\n slab_free_hook mm/slub.c:2338 [inline]\n slab_free mm/slub.c:4598 [inline]\n kmem_cache_free+0x195/0x410 mm/slub.c:4700\n put_task_struct include/linux/sched/task.h:144 [inline]\n delayed_put_task_struct+0x125/0x300 kernel/exit.c:227\n rcu_do_batch kernel/rcu/tree.c:2567 [inline]\n rcu_core+0xaaa/0x17a0 kernel/rcu/tree.c:2823\n handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:554\n run_ksoftirqd+0xca/0x130 kernel/softirq.c:943\n \n---truncated---"
}
],
"metrics": [
{
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"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"scenarios": [
{
"lang": "en",
"value": "AV:L - The attack requires local access to write compressed data to a mounted btrfs filesystem and the local unmount path (`umount(2)` \u2192 `close_ctree()`); there is no remote protocol handler involved.\nAC:L - The attacker fully controls one side of the race and can keep the `delalloc_workers` queue continuously saturated with compressed writeback so that a worker is essentially always in flight, making the UAF fire on any unmount rather than requiring a narrow timing window; where the attacker can also trigger the unmount (removable media via udisks2, container teardown) they control both sides.\nPR:L - Generating the compressed delalloc work needs only an unprivileged user with write access to a btrfs mount \u2014 per-inode compression is settable by the file owner via `chattr +c` (`inode_owner_or_capable`), and many distros mount with `compress=zstd` by default.\nUI:N - No victim action is needed; the unmount that closes the race occurs automatically at shutdown, on container teardown, or on media eject, and in the removable-media case the attacker performs it themselves.\nS:U - The use-after-free is on a kernel `task_struct` and impacts only the kernel\u0027s own security authority, with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - The freed `task_struct` slab object can be reallocated with attacker-groomed content, and the wakeup path reads scheduler fields and pointers from it, giving a path to kernel memory disclosure.\nI:H - `try_to_wake_up()` writes into the freed object (`pi_lock` acquisition, `__state`/`on_rq` updates) and performs indirect calls through `p-\u003esched_class`, providing write and control-flow-hijack primitives on a sprayable slab.\nA:H - The bug is a KASAN-confirmed slab-use-after-free reported by syzbot that reliably oopses or panics the kernel during unmount."
}
]
}
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"title": "btrfs: flush delalloc workers queue before stopping cleaner kthread during unmount",
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"datePublished": "2025-01-15T13:05:48.310Z",
"dateReserved": "2025-01-11T14:45:42.029Z",
"dateUpdated": "2026-08-05T11:46:49.998Z",
"state": "PUBLISHED"
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"cve": "CVE-2024-57896",
"date": "2026-10-25",
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"cve": "CVE-2024-57896",
"id": "msrc_CVE-2024-57896",
"initial_release_date": "2025-01-02T00:00:00.000Z",
"product_status:fixed": "4",
"product_status:known_affected": "4",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "btrfs: flush delalloc workers queue before stopping cleaner kthread during unmount",
"url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2024-57896.json",
"version": "3"
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: flush delalloc workers queue before stopping cleaner kthread during unmount\n\nDuring the unmount path, at close_ctree(), we first stop the cleaner\nkthread, using kthread_stop() which frees the associated task_struct, and\nthen stop and destroy all the work queues. However after we stopped the\ncleaner we may still have a worker from the delalloc_workers queue running\ninode.c:submit_compressed_extents(), which calls btrfs_add_delayed_iput(),\nwhich in turn tries to wake up the cleaner kthread - which was already\ndestroyed before, resulting in a use-after-free on the task_struct.\n\nSyzbot reported this with the following stack traces:\n\n BUG: KASAN: slab-use-after-free in __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089\n Read of size 8 at addr ffff8880259d2818 by task kworker/u8:3/52\n\n CPU: 1 UID: 0 PID: 52 Comm: kworker/u8:3 Not tainted 6.13.0-rc1-syzkaller-00002-gcdd30ebb1b9f #0\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\n Workqueue: btrfs-delalloc btrfs_work_helper\n Call Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0x169/0x550 mm/kasan/report.c:489\n kasan_report+0x143/0x180 mm/kasan/report.c:602\n __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089\n lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]\n _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162\n class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]\n try_to_wake_up+0xc2/0x1470 kernel/sched/core.c:4205\n submit_compressed_extents+0xdf/0x16e0 fs/btrfs/inode.c:1615\n run_ordered_work fs/btrfs/async-thread.c:288 [inline]\n btrfs_work_helper+0x96f/0xc40 fs/btrfs/async-thread.c:324\n process_one_work kernel/workqueue.c:3229 [inline]\n process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310\n worker_thread+0x870/0xd30 kernel/workqueue.c:3391\n kthread+0x2f0/0x390 kernel/kthread.c:389\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n \u003c/TASK\u003e\n\n Allocated by task 2:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x3f/0x80 mm/kasan/common.c:68\n unpoison_slab_object mm/kasan/common.c:319 [inline]\n __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345\n kasan_slab_alloc include/linux/kasan.h:250 [inline]\n slab_post_alloc_hook mm/slub.c:4104 [inline]\n slab_alloc_node mm/slub.c:4153 [inline]\n kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205\n alloc_task_struct_node kernel/fork.c:180 [inline]\n dup_task_struct+0x57/0x8c0 kernel/fork.c:1113\n copy_process+0x5d1/0x3d50 kernel/fork.c:2225\n kernel_clone+0x223/0x870 kernel/fork.c:2807\n kernel_thread+0x1bc/0x240 kernel/fork.c:2869\n create_kthread kernel/kthread.c:412 [inline]\n kthreadd+0x60d/0x810 kernel/kthread.c:767\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n\n Freed by task 24:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x3f/0x80 mm/kasan/common.c:68\n kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582\n poison_slab_object mm/kasan/common.c:247 [inline]\n __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264\n kasan_slab_free include/linux/kasan.h:233 [inline]\n slab_free_hook mm/slub.c:2338 [inline]\n slab_free mm/slub.c:4598 [inline]\n kmem_cache_free+0x195/0x410 mm/slub.c:4700\n put_task_struct include/linux/sched/task.h:144 [inline]\n delayed_put_task_struct+0x125/0x300 kernel/exit.c:227\n rcu_do_batch kernel/rcu/tree.c:2567 [inline]\n rcu_core+0xaaa/0x17a0 kernel/rcu/tree.c:2823\n handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:554\n run_ksoftirqd+0xca/0x130 kernel/softirq.c:943\n \n---truncated---"
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: vaciar la cola de trabajadores delalloc antes de detener el kthread del limpiador durante el desmontaje Durante la ruta de desmontaje, en close_ctree(), primero detenemos el kthread del limpiador, utilizando kthread_stop() que libera el task_struct asociado, y luego detenemos y destruimos todas las colas de trabajo. Sin embargo, despu\u00e9s de detener el limpiador, es posible que a\u00fan tengamos un trabajador de la cola delalloc_workers ejecutando inode.c:submit_compressed_extents(), que llama a btrfs_add_delayed_iput(), que a su vez intenta despertar el kthread del limpiador, que ya se destruy\u00f3 antes, lo que resulta en un uso despu\u00e9s de la liberaci\u00f3n en el task_struct. Syzbot inform\u00f3 esto con los siguientes seguimientos de pila: ERROR: KASAN: slab-use-after-free en __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089 Lectura de tama\u00f1o 8 en la direcci\u00f3n ffff8880259d2818 por la tarea kworker/u8:3/52 CPU: 1 UID: 0 PID: 52 Comm: kworker/u8:3 No contaminado 6.13.0-rc1-syzkaller-00002-gcdd30ebb1b9f #0 Nombre del hardware: Google Google Compute Engine/Google Compute Engine, BIOS Google 13/09/2024 Cola de trabajo: btrfs-delalloc btrfs_work_helper Seguimiento de llamadas: __dump_stack lib/dump_stack.c:94 [en l\u00ednea] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [en l\u00ednea] print_report+0x169/0x550 mm/kasan/report.c:489 kasan_report+0x143/0x180 mm/kasan/report.c:602 __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __raw_spin_lock_irqsave incluir/linux/spinlock_api_smp.h:110 [en l\u00ednea] _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162 class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [en l\u00ednea] try_to_wake_up+0xc2/0x1470 kernel/sched/core.c:4205 submit_compressed_extents+0xdf/0x16e0 fs/btrfs/inode.c:1615 run_ordered_work fs/btrfs/async-thread.c:288 [en l\u00ednea] btrfs_work_helper+0x96f/0xc40 fs/btrfs/async-thread.c:324 process_one_work kernel/workqueue.c:3229 [en l\u00ednea] process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310 Asignado por la tarea 2: kasan_save_stack mm/kasan/common.c:47 [en l\u00ednea] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 unpoison_slab_object mm/kasan/common.c:319 [en l\u00ednea] __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345 kasan_slab_alloc include/linux/kasan.h:250 [en l\u00ednea] gancho de alloc de publicaci\u00f3n de losa mm/slub.c:4104 [en l\u00ednea] nodo de alloc de losa mm/slub.c:4153 [en l\u00ednea] nodo de alloc de cach\u00e9 kmem_noprof+0x1d9/0x380 mm/slub.c:4205 nodo de estructura de tareas de asignaci\u00f3n kernel/fork.c:180 [en l\u00ednea] estructura de tareas dup+0x57/0x8c0 kernel/fork.c:1113 proceso de copia+0x5d1/0x3d50 kernel/fork.c:2225 clon de kernel+0x223/0x870 kernel/fork.c:2807 kernel_thread+0x1bc/0x240 kernel/fork.c:2869 create_kthread kernel/kthread.c:412 [en l\u00ednea] kthreadd+0x60d/0x810 kernel/kthread.c:767 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Liberado por la tarea 24: kasan_save_stack mm/kasan/common.c:47 [en l\u00ednea] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582 poison_slab_object mm/kasan/common.c:247 [en l\u00ednea] __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264 kasan_slab_free include/linux/kasan.h:233 [en l\u00ednea] gancho slab_free mm/slub.c:2338 [en l\u00ednea] slab_free mm/slub.c:4598 [en l\u00ednea] kmem_cache_free+0x195/0x410 mm/slub.c:4700 put_task_struct include/linux/sched/task.h:144 [en l\u00ednea] delayed_put_task_struct+0x125/0x300 kernel/exit.c:227 rcu_do_batch kernel/rcu/tree.c:2567 [en l\u00ednea] rcu_core+0xaaa/0x17a0 kernel/rcu/tree.c:2823 handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:554 run_ksoftirqd+0xca/0x130 kernel/softirq.c:943 ---truncado---"
}
],
"id": "CVE-2024-57896",
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"lessThan": "f10bef73fb355e3fc85e63a50386798be68ff486",
"status": "affected",
"version": "fd340d0f68cc87badfc9efcb226f23a5428826a0",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/btrfs/disk-io.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.0"
},
{
"lessThan": "5.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.233",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.176",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.124",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.70",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.9",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "6.13",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.233",
"versionStartIncluding": "5.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.176",
"versionStartIncluding": "5.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.124",
"versionStartIncluding": "5.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.70",
"versionStartIncluding": "5.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.9",
"versionStartIncluding": "5.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.13",
"versionStartIncluding": "5.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: flush delalloc workers queue before stopping cleaner kthread during unmount\n\nDuring the unmount path, at close_ctree(), we first stop the cleaner\nkthread, using kthread_stop() which frees the associated task_struct, and\nthen stop and destroy all the work queues. However after we stopped the\ncleaner we may still have a worker from the delalloc_workers queue running\ninode.c:submit_compressed_extents(), which calls btrfs_add_delayed_iput(),\nwhich in turn tries to wake up the cleaner kthread - which was already\ndestroyed before, resulting in a use-after-free on the task_struct.\n\nSyzbot reported this with the following stack traces:\n\n BUG: KASAN: slab-use-after-free in __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089\n Read of size 8 at addr ffff8880259d2818 by task kworker/u8:3/52\n\n CPU: 1 UID: 0 PID: 52 Comm: kworker/u8:3 Not tainted 6.13.0-rc1-syzkaller-00002-gcdd30ebb1b9f #0\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\n Workqueue: btrfs-delalloc btrfs_work_helper\n Call Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0x169/0x550 mm/kasan/report.c:489\n kasan_report+0x143/0x180 mm/kasan/report.c:602\n __lock_acquire+0x78/0x2100 kernel/locking/lockdep.c:5089\n lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]\n _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162\n class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]\n try_to_wake_up+0xc2/0x1470 kernel/sched/core.c:4205\n submit_compressed_extents+0xdf/0x16e0 fs/btrfs/inode.c:1615\n run_ordered_work fs/btrfs/async-thread.c:288 [inline]\n btrfs_work_helper+0x96f/0xc40 fs/btrfs/async-thread.c:324\n process_one_work kernel/workqueue.c:3229 [inline]\n process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310\n worker_thread+0x870/0xd30 kernel/workqueue.c:3391\n kthread+0x2f0/0x390 kernel/kthread.c:389\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n \u003c/TASK\u003e\n\n Allocated by task 2:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x3f/0x80 mm/kasan/common.c:68\n unpoison_slab_object mm/kasan/common.c:319 [inline]\n __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345\n kasan_slab_alloc include/linux/kasan.h:250 [inline]\n slab_post_alloc_hook mm/slub.c:4104 [inline]\n slab_alloc_node mm/slub.c:4153 [inline]\n kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205\n alloc_task_struct_node kernel/fork.c:180 [inline]\n dup_task_struct+0x57/0x8c0 kernel/fork.c:1113\n copy_process+0x5d1/0x3d50 kernel/fork.c:2225\n kernel_clone+0x223/0x870 kernel/fork.c:2807\n kernel_thread+0x1bc/0x240 kernel/fork.c:2869\n create_kthread kernel/kthread.c:412 [inline]\n kthreadd+0x60d/0x810 kernel/kthread.c:767\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n\n Freed by task 24:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x3f/0x80 mm/kasan/common.c:68\n kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582\n poison_slab_object mm/kasan/common.c:247 [inline]\n __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264\n kasan_slab_free include/linux/kasan.h:233 [inline]\n slab_free_hook mm/slub.c:2338 [inline]\n slab_free mm/slub.c:4598 [inline]\n kmem_cache_free+0x195/0x410 mm/slub.c:4700\n put_task_struct include/linux/sched/task.h:144 [inline]\n delayed_put_task_struct+0x125/0x300 kernel/exit.c:227\n rcu_do_batch kernel/rcu/tree.c:2567 [inline]\n rcu_core+0xaaa/0x17a0 kernel/rcu/tree.c:2823\n handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:554\n run_ksoftirqd+0xca/0x130 kernel/softirq.c:943\n \n---truncated---"
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The attack requires local access to write compressed data to a mounted btrfs filesystem and the local unmount path (`umount(2)` \u2192 `close_ctree()`); there is no remote protocol handler involved.\nAC:L - The attacker fully controls one side of the race and can keep the `delalloc_workers` queue continuously saturated with compressed writeback so that a worker is essentially always in flight, making the UAF fire on any unmount rather than requiring a narrow timing window; where the attacker can also trigger the unmount (removable media via udisks2, container teardown) they control both sides.\nPR:L - Generating the compressed delalloc work needs only an unprivileged user with write access to a btrfs mount \u2014 per-inode compression is settable by the file owner via `chattr +c` (`inode_owner_or_capable`), and many distros mount with `compress=zstd` by default.\nUI:N - No victim action is needed; the unmount that closes the race occurs automatically at shutdown, on container teardown, or on media eject, and in the removable-media case the attacker performs it themselves.\nS:U - The use-after-free is on a kernel `task_struct` and impacts only the kernel\u0027s own security authority, with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - The freed `task_struct` slab object can be reallocated with attacker-groomed content, and the wakeup path reads scheduler fields and pointers from it, giving a path to kernel memory disclosure.\nI:H - `try_to_wake_up()` writes into the freed object (`pi_lock` acquisition, `__state`/`on_rq` updates) and performs indirect calls through `p-\u003esched_class`, providing write and control-flow-hijack primitives on a sprayable slab.\nA:H - The bug is a KASAN-confirmed slab-use-after-free reported by syzbot that reliably oopses or panics the kernel during unmount."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T11:46:49.998Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/a2718ed1eb8c3611b63f8933c7e68c8821fe2808"
},
{
"url": "https://git.kernel.org/stable/c/63f4b594a688bf922e8691f0784679aa7af7988c"
},
{
"url": "https://git.kernel.org/stable/c/1ea629e7bb2fb40555e5e01a1b5095df31287017"
},
{
"url": "https://git.kernel.org/stable/c/35916b2f96505a18dc7242a115611b718d9de725"
},
{
"url": "https://git.kernel.org/stable/c/d77a3a99b53d12c061c007cdc96df38825dee476"
},
{
"url": "https://git.kernel.org/stable/c/f10bef73fb355e3fc85e63a50386798be68ff486"
}
],
"title": "btrfs: flush delalloc workers queue before stopping cleaner kthread during unmount",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2024-57896",
"datePublished": "2025-01-15T13:05:48.310Z",
"dateReserved": "2025-01-11T14:45:42.029Z",
"dateUpdated": "2026-08-05T11:46:49.998Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.