==================================================================
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:304 [inline]
BUG: KASAN: out-of-bounds in end_buffer_read_sync+0xc3/0xe0 fs/buffer.c:161
Write of size 4 at addr ffffc90003087700 by task kworker/u8:4/59

CPU: 1 UID: 0 PID: 59 Comm: kworker/u8:4 Not tainted 6.16.0-rc7-syzkaller-00120-g5f33ebd2018c #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: loop5 loop_rootcg_workfn
Call Trace:
 <IRQ>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:189
 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:304 [inline]
 end_buffer_read_sync+0xc3/0xe0 fs/buffer.c:161
 end_bio_bh_io_sync+0xbd/0x120 fs/buffer.c:2783
 blk_update_request+0x5eb/0xe70 block/blk-mq.c:987
 blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1149
 blk_complete_reqs block/blk-mq.c:1224 [inline]
 blk_done_softirq+0x107/0x160 block/blk-mq.c:1229
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 common_interrupt+0xbb/0xe0 arch/x86/kernel/irq.c:285
 </IRQ>
 <TASK>
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
RIP: 0010:kasan_mem_to_shadow include/linux/kasan.h:65 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:129 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:161 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x61/0x2c0 mm/kasan/generic.c:189
Code: 1e fa 49 b9 00 00 00 00 00 00 00 ff f3 0f 1e fa 4c 39 cf 0f 82 58 02 00 00 49 89 ff 49 c1 ef 03 49 ba 00 00 00 00 00 fc ff df <4f> 8d 1c 17 49 ff c8 4d 89 c1 49 c1 e9 03 48 bb 01 00 00 00 00 fc
RSP: 0018:ffffc9000211f4f0 EFLAGS: 00000a03
RAX: ffffffff81fe7c01 RBX: 0000000000001000 RCX: ffffffff81fe7cf9
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffea0001d2dcf4
RBP: ffffea0001d2dcc0 R08: ffffea0001d2dcf8 R09: ffff800000000000
R10: dffffc0000000000 R11: fffff940003a5b9f R12: ffff888025377ab0
R13: 0000000000001000 R14: 0000000000000003 R15: 1ffffd40003a5b9e
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1383 [inline]
 page_ref_dec_and_test include/linux/page_ref.h:205 [inline]
 put_page_testzero include/linux/mm.h:1035 [inline]
 folio_put_testzero include/linux/mm.h:1040 [inline]
 folio_put include/linux/mm.h:1355 [inline]
 shmem_file_read_iter+0x5a9/0x930 mm/shmem.c:3418
 lo_rw_aio+0xcfa/0xfa0 include/linux/percpu-rwsem.h:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1888 [inline]
 loop_process_work+0x810/0xf40 drivers/block/loop.c:1923
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3321
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

The buggy address belongs to a 8-page vmalloc region starting at 0xffffc90003080000 allocated at copy_process+0x544/0x3b80 kernel/fork.c:1999
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2f7a7
memcg:ffff88802f8b4682
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff ffff88802f8b4682
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_ZERO|__GFP_NOWARN), pid 6550, tgid 6550 (syz.5.78), ts 139572990068, free_ts 139024403592
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x21d5/0x22b0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 alloc_frozen_pages_noprof mm/mempolicy.c:2490 [inline]
 alloc_pages_noprof+0xa9/0x190 mm/mempolicy.c:2510
 vm_area_alloc_pages mm/vmalloc.c:3642 [inline]
 __vmalloc_area_node mm/vmalloc.c:3720 [inline]
 __vmalloc_node_range_noprof+0x97d/0x12f0 mm/vmalloc.c:3893
 __vmalloc_node_noprof+0xc2/0x110 mm/vmalloc.c:3956
 alloc_thread_stack_node kernel/fork.c:317 [inline]
 dup_task_struct+0x3e7/0x860 kernel/fork.c:877
 copy_process+0x544/0x3b80 kernel/fork.c:1999
 kernel_clone+0x224/0x7f0 kernel/fork.c:2599
 __do_sys_clone3 kernel/fork.c:2903 [inline]
 __se_sys_clone3+0x256/0x2d0 kernel/fork.c:2882
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5919 tgid 5919 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0xc65/0xe60 mm/page_alloc.c:2706
 vfree+0x25a/0x400 mm/vmalloc.c:3434
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3353
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3321
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffffc90003087600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003087680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90003087700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                      ^
 ffffc90003087780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003087800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	fa                   	cli
   1:	49 b9 00 00 00 00 00 	movabs $0xff00000000000000,%r9
   8:	00 00 ff
   b:	f3 0f 1e fa          	endbr64
   f:	4c 39 cf             	cmp    %r9,%rdi
  12:	0f 82 58 02 00 00    	jb     0x270
  18:	49 89 ff             	mov    %rdi,%r15
  1b:	49 c1 ef 03          	shr    $0x3,%r15
  1f:	49 ba 00 00 00 00 00 	movabs $0xdffffc0000000000,%r10
  26:	fc ff df
* 29:	4f 8d 1c 17          	lea    (%r15,%r10,1),%r11 <-- trapping instruction
  2d:	49 ff c8             	dec    %r8
  30:	4d 89 c1             	mov    %r8,%r9
  33:	49 c1 e9 03          	shr    $0x3,%r9
  37:	48                   	rex.W
  38:	bb 01 00 00 00       	mov    $0x1,%ebx
  3d:	00 fc                	add    %bh,%ah