KASAN: slab-use-after-free Write in do_bad_area

Status: upstream: reported on 2026/08/25 00:39
Subsystems: fs
Labels: prio:normal actionable
[Documentation on labels]
Reported-by: syzbot+7bf725ed337e37307001@syzkaller.appspotmail.com
First crash: 4d09h, last: 4d09h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
ea9af2a8 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Write in do_bad_area 2026/08/25 00:26 2026/08/25 00:26 2026/08/25 00:39 23caa175
3e9822cf assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Write in do_bad_area 2026/08/22 00:00 2026/08/22 00:00 2026/08/22 00:32 1e72964b
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [fs?] KASAN: slab-use-after-free Write in do_bad_area 0 (1) 2026/08/25 00:39
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: invalid-access Write in do_bad_area bpf -1 syz, C 34838 238d 323d 29/29 fixed on 2026/01/26 05:07

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __lse__cmpxchg_case_acq_64 arch/arm64/include/asm/atomic_lse.h:272 [inline]
BUG: KASAN: slab-use-after-free in __cmpxchg_case_acq_64 arch/arm64/include/asm/cmpxchg.h:122 [inline]
BUG: KASAN: slab-use-after-free in __cmpxchg_acq arch/arm64/include/asm/cmpxchg.h:170 [inline]
BUG: KASAN: slab-use-after-free in raw_atomic64_cmpxchg_acquire include/linux/atomic/atomic-arch-fallback.h:4181 [inline]
BUG: KASAN: slab-use-after-free in raw_atomic64_try_cmpxchg_acquire include/linux/atomic/atomic-arch-fallback.h:4299 [inline]
BUG: KASAN: slab-use-after-free in raw_atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-long.h:1482 [inline]
BUG: KASAN: slab-use-after-free in atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4458 [inline]
BUG: KASAN: slab-use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:161 [inline]
BUG: KASAN: slab-use-after-free in mutex_lock_interruptible+0x10/0x70 kernel/locking/mutex.c:1109
Write at addr faf00000079e3f00 by task syz-executor/3375
Pointer tag: [fa], memory tag: [fe]

CPU: 0 UID: 0 PID: 3375 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT 
Tainted: [L]=SOFTLOCKUP
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace arch/arm64/kernel/stacktrace.c:498 [inline] (C)
 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x60/0x80 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x1c4/0x4b0 mm/kasan/report.c:482
 kasan_report+0x84/0xac mm/kasan/report.c:595
 report_tag_fault arch/arm64/mm/fault.c:368 [inline]
 do_tag_recovery arch/arm64/mm/fault.c:380 [inline]
 __do_kernel_fault+0x1b4/0x220 arch/arm64/mm/fault.c:424
 do_bad_area+0x68/0x80 arch/arm64/mm/fault.c:529
 do_tag_check_fault+0x34/0x44 arch/arm64/mm/fault.c:909
 do_mem_abort+0x40/0x90 arch/arm64/mm/fault.c:985
 el1_abort+0x44/0x64 arch/arm64/kernel/entry-common.c:342
 el1h_64_sync_handler+0x50/0xac arch/arm64/kernel/entry-common.c:469
 el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:585
 __lse__cmpxchg_case_acq_64 arch/arm64/include/asm/atomic_lse.h:272 [inline] (P)
 __cmpxchg_case_acq_64 arch/arm64/include/asm/cmpxchg.h:122 [inline] (P)
 __cmpxchg_acq arch/arm64/include/asm/cmpxchg.h:170 [inline] (P)
 raw_atomic64_cmpxchg_acquire include/linux/atomic/atomic-arch-fallback.h:4181 [inline] (P)
 raw_atomic64_try_cmpxchg_acquire include/linux/atomic/atomic-arch-fallback.h:4299 [inline] (P)
 raw_atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-long.h:1482 [inline] (P)
 atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4458 [inline] (P)
 __mutex_trylock_fast kernel/locking/mutex.c:161 [inline] (P)
 mutex_lock_interruptible+0x10/0x70 kernel/locking/mutex.c:1109 (P)
 do_dentry_open+0x128/0x4fc fs/open.c:996
 vfs_open+0x2c/0xe8 fs/open.c:1101
 do_open fs/namei.c:4837 [inline]
 path_openat+0x5b4/0x960 fs/namei.c:5000
 do_file_open+0xb0/0x168 fs/namei.c:5029
 do_sys_openat2+0x84/0x104 fs/open.c:1417
 do_sys_open fs/open.c:1423 [inline]
 __do_sys_openat fs/open.c:1439 [inline]
 __se_sys_openat fs/open.c:1434 [inline]
 __arm64_sys_openat+0x64/0xc0 fs/open.c:1434
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x54/0x10c arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x1c/0x34 arch/arm64/kernel/syscall.c:140
 el0_svc+0x38/0x1fc arch/arm64/kernel/entry-common.c:758
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:590

Allocated by task 4267:
 kasan_save_stack+0x3c/0x64 mm/kasan/common.c:57
 save_stack_info+0x40/0x160 mm/kasan/tags.c:106
 kasan_save_alloc_info+0x14/0x20 mm/kasan/tags.c:142
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 poison_kmalloc_redzone mm/kasan/common.c:371 [inline]
 __kasan_kmalloc+0xf8/0x120 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x1c0/0x460 mm/slub.c:5489
 _kmalloc_noprof include/linux/slab.h:988 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 activate_ep_files drivers/usb/gadget/legacy/inode.c:1601 [inline]
 gadgetfs_bind+0xd0/0x3c0 drivers/usb/gadget/legacy/inode.c:1692
 gadget_bind_driver+0x90/0x284 drivers/usb/gadget/udc/core.c:1662
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0xbc/0x2bc drivers/base/dd.c:706
 __driver_probe_device+0x11c/0x184 drivers/base/dd.c:868
 driver_probe_device+0x3c/0x114 drivers/base/dd.c:898
 __driver_attach+0x90/0x180 drivers/base/dd.c:1292
 bus_for_each_dev+0x7c/0xdc drivers/base/bus.c:383
 driver_attach+0x24/0x30 drivers/base/dd.c:1310
 bus_add_driver+0xe4/0x208 drivers/base/bus.c:763
 driver_register+0x68/0x130 drivers/base/driver.c:174
 usb_gadget_register_driver_owner+0x54/0xfc drivers/usb/gadget/udc/core.c:1752
 dev_config+0x214/0x484 drivers/usb/gadget/legacy/inode.c:1883
 vfs_write+0xd4/0x36c fs/read_write.c:685
 ksys_write+0x70/0x108 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __arm64_sys_write+0x18/0x24 fs/read_write.c:747
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x54/0x10c arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x1c/0x34 arch/arm64/kernel/syscall.c:140
 el0_svc+0x38/0x1fc arch/arm64/kernel/entry-common.c:758
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:590

Freed by task 3478:
 kasan_save_stack+0x3c/0x64 mm/kasan/common.c:57
 save_stack_info+0x40/0x160 mm/kasan/tags.c:106
 kasan_save_free_info+0x18/0x40 mm/kasan/tags.c:147
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0xe8/0x160 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x150/0x41c mm/slub.c:6692
 put_ep.part.0+0x44/0x60 drivers/usb/gadget/legacy/inode.c:225
 put_ep include/linux/refcount.h:396 [inline]
 destroy_ep_files+0x104/0x170 drivers/usb/gadget/legacy/inode.c:1582
 gadgetfs_unbind+0x7c/0xc0 drivers/usb/gadget/legacy/inode.c:1655
 gadget_unbind_driver+0x7c/0x118 drivers/usb/gadget/udc/core.c:1724
 device_remove+0x4c/0x80 drivers/base/dd.c:616
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x1cc/0x224 drivers/base/dd.c:1372
 driver_detach+0x4c/0xb0 drivers/base/dd.c:1435
 bus_remove_driver+0x6c/0xbc drivers/base/bus.c:832
 driver_unregister+0x30/0x60 drivers/base/driver.c:202
 usb_gadget_unregister_driver+0x20/0x40 drivers/usb/gadget/udc/core.c:1784
 dev_release+0x68/0x80 drivers/usb/gadget/legacy/inode.c:1198
 __fput+0xcc/0x2f8 fs/file_table.c:512
 delayed_fput+0x50/0x6c fs/file_table.c:535
 process_one_work+0x180/0x2d0 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x18c/0x300 kernel/workqueue.c:3486
 kthread+0x118/0x130 kernel/kthread.c:436
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854

The buggy address belongs to the object at fff00000079e3f00
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes inside of
 192-byte region [fff00000079e3f00, fff00000079e3fc0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x479e3
flags: 0x1ffc00000000000(node=0|zone=0|lastcpupid=0x7ff|kasantag=0x0)
page_type: f5(slab)
raw: 01ffc00000000000 f9f0000003401300 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800150015 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 fff00000079e3d00: f9 f9 f9 f9 f9 f9 f9 f9 fb fb fb fb fb fb fb fb
 fff00000079e3e00: fb fb fb fb fe fe fe fe fe fe fe fe fe fe fe fe
>fff00000079e3f00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                   ^
 fff00000079e4000: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 fff00000079e4100: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/20 17:13 https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux master a4ff2be345d0 1e72964b .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte KASAN: slab-use-after-free Write in do_bad_area
* Struck through repros no longer work on HEAD.