KASAN: use-after-free Read in gfs2

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KASAN: slab-use-after-free Read in gfs2_logd gfs2	19				6	54d	65d	0/29	upstream: reported on 2026/01/13 03:22
==================================================================
BUG: KASAN: use-after-free in generic_test_bit include/asm-generic/bitops/generic-non-atomic.h:128 [inline]
BUG: KASAN: use-after-free in gfs2_withdrawn fs/gfs2/util.h:208 [inline]
BUG: KASAN: use-after-free in gfs2_logd+0x120/0xbf0 fs/gfs2/log.c:1306
Read of size 8 at addr ffff0000d46240a8 by task gfs2_logd/5466

CPU: 0 PID: 5466 Comm: gfs2_logd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
Call trace:
 dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_load8_noabort+0x2c/0x38 mm/kasan/report_generic.c:351
 generic_test_bit include/asm-generic/bitops/generic-non-atomic.h:128 [inline]
 gfs2_withdrawn fs/gfs2/util.h:208 [inline]
 gfs2_logd+0x120/0xbf0 fs/gfs2/log.c:1306
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Allocated by task 5426:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 kmalloc_trace+0x7c/0x94 mm/slab_common.c:1031
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 init_sbd fs/gfs2/ops_fstype.c:77 [inline]
 gfs2_fill_super+0x108/0x194c fs/gfs2/ops_fstype.c:1148
 get_tree_bdev+0x358/0x544 fs/super.c:1366
 gfs2_get_tree+0x54/0x1b4 fs/gfs2/ops_fstype.c:1327
 vfs_get_tree+0x90/0x274 fs/super.c:1573
 do_new_mount+0x228/0x810 fs/namespace.c:3078
 path_mount+0x5bc/0xe80 fs/namespace.c:3408
 do_mount fs/namespace.c:3421 [inline]
 __do_sys_mount fs/namespace.c:3629 [inline]
 __se_sys_mount fs/namespace.c:3606 [inline]
 __arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Freed by task 7128:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
 ____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xbc/0x218 mm/slub.c:3700
 kfree+0xd0/0x1a8 mm/slab_common.c:988
 free_sbd+0x5c/0x6c fs/gfs2/ops_fstype.c:69
 gfs2_put_super+0x6f8/0x760 fs/gfs2/super.c:649
 generic_shutdown_super+0x130/0x324 fs/super.c:501
 kill_block_super+0x70/0xdc fs/super.c:1470
 gfs2_kill_sb+0xc0/0xd4 fs/gfs2/ops_fstype.c:-1
 deactivate_locked_super+0xac/0x120 fs/super.c:332
 deactivate_super+0xe4/0x104 fs/super.c:363
 cleanup_mnt+0x390/0x418 fs/namespace.c:1191
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198
 task_work_run+0x1ec/0x278 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0x550/0x19b0 kernel/exit.c:880
 do_group_exit+0x194/0x22c kernel/exit.c:1022
 get_signal+0x11cc/0x1304 kernel/signal.c:2871
 do_signal arch/arm64/kernel/signal.c:1095 [inline]
 do_notify_resume+0x28c/0x2aa4 arch/arm64/kernel/signal.c:1148
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_da+0xb4/0x144 arch/arm64/kernel/entry-common.c:516
 el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Last potentially related work creation:
 kasan_save_stack+0x40/0x70 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xc0/0xdc mm/kasan/generic.c:486
 kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:496
 kvfree_call_rcu+0xb4/0x6e8 kernel/rcu/tree.c:3405
 cgroup_free_root kernel/cgroup/cgroup.c:1372 [inline]
 cgroup_destroy_root kernel/cgroup/cgroup.c:1416 [inline]
 css_free_rwork_fn+0x78c/0xb94 kernel/cgroup/cgroup.c:5414
 process_one_work+0x7f8/0x13a4 kernel/workqueue.c:2292
 worker_thread+0x8c4/0xfec kernel/workqueue.c:2439
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Second to last potentially related work creation:
 kasan_save_stack+0x40/0x70 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xc0/0xdc mm/kasan/generic.c:486
 kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:496
 insert_work+0x64/0x37c kernel/workqueue.c:1361
 __queue_work+0xcbc/0x1234 kernel/workqueue.c:1520
 rcu_work_rcufn+0x94/0xb0 kernel/workqueue.c:1757
 rcu_do_batch kernel/rcu/tree.c:2297 [inline]
 rcu_core+0x828/0x18b0 kernel/rcu/tree.c:2557
 rcu_core_si+0x10/0x1c kernel/rcu/tree.c:2574
 handle_softirqs+0x318/0xc60 kernel/softirq.c:596
 __do_softirq+0x14/0x20 kernel/softirq.c:630

The buggy address belongs to the object at ffff0000d4624000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 168 bytes inside of
 8192-byte region [ffff0000d4624000, ffff0000d4626000)

The buggy address belongs to the physical page:
page:000000009acd3d8e refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x114620
head:000000009acd3d8e order:3 compound_mapcount:0 compound_pincount:0
flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000010200 fffffc000405d200 dead000000000002 ffff0000c0002c00
raw: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d4623f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000d4624000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff0000d4624080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff0000d4624100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d4624180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Assets (help?)	Manager	Title
2026/03/18 14:37	linux-6.1.y	f2ddafa93a25	0199f9a1	.config	console log	report			info	[disk image] [vmlinux] [kernel image]	ci2-linux-6-1-kasan-arm64	KASAN: use-after-free Read in gfs2_logd
2026/03/18 14:34	linux-6.1.y	f2ddafa93a25	0199f9a1	.config	console log	report			info	[disk image] [vmlinux] [kernel image]	ci2-linux-6-1-kasan-arm64	KASAN: use-after-free Read in gfs2_logd