==================================================================
BUG: KASAN: out-of-bounds in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: out-of-bounds in atomic_dec include/linux/atomic/atomic-instrumented.h:592 [inline]
BUG: KASAN: out-of-bounds in put_bh include/linux/buffer_head.h:308 [inline]
BUG: KASAN: out-of-bounds in end_buffer_read_sync+0xc3/0xd0 fs/buffer.c:161
Write of size 4 at addr ffffc9000b25f740 by task kworker/u4:1/12

CPU: 0 PID: 12 Comm: kworker/u4:1 Not tainted 6.6.102-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: loop7 loop_workfn
Call Trace:
 <IRQ>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x220 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x288/0x290 mm/kasan/generic.c:187
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_dec include/linux/atomic/atomic-instrumented.h:592 [inline]
 put_bh include/linux/buffer_head.h:308 [inline]
 end_buffer_read_sync+0xc3/0xd0 fs/buffer.c:161
 end_bio_bh_io_sync+0xb7/0x110 fs/buffer.c:2784
 req_bio_endio block/blk-mq.c:784 [inline]
 blk_update_request+0x597/0xe40 block/blk-mq.c:929
 blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1056
 blk_complete_reqs block/blk-mq.c:1136 [inline]
 blk_done_softirq+0x10b/0x160 block/blk-mq.c:1141
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_call_function_single arch/x86/kernel/smp.c:262 [inline]
 sysvec_call_function_single+0xa1/0xc0 arch/x86/kernel/smp.c:262
 </IRQ>
 <TASK>
 asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:694
RIP: 0010:raise_softirq+0xfd/0x150 kernel/softirq.c:718
Code: 4c 3a 00 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 45 41 f7 c7 00 02 00 00 74 01 fb 48 c7 04 24 0e 36 e0 45 <4a> c7 04 33 00 00 00 00 66 42 c7 44 33 09 00 00 42 c6 44 33 0b 00
RSP: 0018:ffffc90000117820 EFLAGS: 00000206
RAX: f7e3236b1ff18800 RBX: 1ffff92000022f04 RCX: f7e3236b1ff18800
RDX: dffffc0000000000 RSI: ffffffff8aaab9c0 RDI: ffffffff8afc66c0
RBP: ffffc900001178d0 R08: ffffffff90da35ff R09: 1ffffffff21b46bf
R10: dffffc0000000000 R11: fffffbfff21b46c0 R12: 0000000000000004
R13: 1ffff1100431b050 R14: dffffc0000000000 R15: 0000000000000a02
 blk_mq_raise_softirq block/blk-mq.c:1197 [inline]
 blk_mq_complete_request_remote+0x4e1/0x6c0 block/blk-mq.c:1221
 blk_mq_complete_request+0x19/0xa0 block/blk-mq.c:1237
 loop_handle_cmd drivers/block/loop.c:1928 [inline]
 loop_process_work+0x185b/0x1ed0 drivers/block/loop.c:1946
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

The buggy address belongs to a 8-page vmalloc region starting at 0xffffc9000b258000 allocated at copy_process+0x549/0x3d70 kernel/fork.c:2331
The buggy address belongs to the physical page:
page:ffffea0000bc3000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2f0c0
memcg:ffff888020c61482
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff ffff888020c61482
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x102dc2(GFP_HIGHUSER|__GFP_NOWARN|__GFP_ZERO), pid 7600, tgid 7600 (syz.5.417), ts 247918784802, free_ts 244988207130
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 vm_area_alloc_pages mm/vmalloc.c:3089 [inline]
 __vmalloc_area_node mm/vmalloc.c:3158 [inline]
 __vmalloc_node_range+0x96b/0x1320 mm/vmalloc.c:3339
 alloc_thread_stack_node kernel/fork.c:310 [inline]
 dup_task_struct+0x3d0/0x7c0 kernel/fork.c:1124
 copy_process+0x549/0x3d70 kernel/fork.c:2331
 kernel_clone+0x21b/0x840 kernel/fork.c:2914
 __do_sys_clone3 kernel/fork.c:3215 [inline]
 __se_sys_clone3+0x252/0x2c0 kernel/fork.c:3199
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 __folio_batch_release+0x71/0xe0 mm/swap.c:1042
 folio_batch_release include/linux/pagevec.h:83 [inline]
 invalidate_inode_pages2_range+0xc45/0xe10 mm/truncate.c:679
 close_ctree+0x6b6/0xca0 fs/btrfs/disk-io.c:4457
 generic_shutdown_super+0x134/0x2b0 fs/super.c:693
 kill_anon_super+0x3b/0x70 fs/super.c:1303
 btrfs_kill_super+0x41/0x50 fs/btrfs/super.c:2146
 deactivate_locked_super+0x97/0x100 fs/super.c:481
 cleanup_mnt+0x429/0x4c0 fs/namespace.c:1250
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87

Memory state around the buggy address:
 ffffc9000b25f600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc9000b25f680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc9000b25f700: 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 f2
                                              ^
 ffffc9000b25f780: f2 f2 f2 f2 00 f2 f2 f2 01 f3 f3 f3 00 00 00 00
 ffffc9000b25f800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
vkms_vblank_simulate: vblank timer overrun
----------------
Code disassembly (best guess):
   0:	4c 3a 00             	rex.WR cmp (%rax),%r8b
   3:	48 c7 44 24 20 00 00 	movq   $0x0,0x20(%rsp)
   a:	00 00
   c:	9c                   	pushf
   d:	8f 44 24 20          	pop    0x20(%rsp)
  11:	f6 44 24 21 02       	testb  $0x2,0x21(%rsp)
  16:	75 45                	jne    0x5d
  18:	41 f7 c7 00 02 00 00 	test   $0x200,%r15d
  1f:	74 01                	je     0x22
  21:	fb                   	sti
  22:	48 c7 04 24 0e 36 e0 	movq   $0x45e0360e,(%rsp)
  29:	45
* 2a:	4a c7 04 33 00 00 00 	movq   $0x0,(%rbx,%r14,1) <-- trapping instruction
  31:	00
  32:	66 42 c7 44 33 09 00 	movw   $0x0,0x9(%rbx,%r14,1)
  39:	00
  3a:	42 c6 44 33 0b 00    	movb   $0x0,0xb(%rbx,%r14,1)