================================================================== 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 ffffc900048ef700 by task kworker/u8:4/59 CPU: 0 UID: 0 PID: 59 Comm: kworker/u8:4 Not tainted 6.16.0-rc5-syzkaller-00276-g5d5d62298b8b #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: loop4 loop_workfn Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x230 mm/kasan/report.c:480 kasan_report+0x118/0x150 mm/kasan/report.c:593 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+0x10a/0x160 block/blk-mq.c:1229 handle_softirqs+0x286/0x870 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 instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline] sysvec_call_function_single+0xa3/0xc0 arch/x86/kernel/smp.c:266 asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709 RIP: 0010:raise_softirq+0xcc/0x120 kernel/softirq.c:741 Code: fd 41 00 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 49 41 f7 c4 00 02 00 00 74 01 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 66 43 c7 44 3e 09 00 00 43 c6 44 3e 0b 00 RSP: 0018:ffffc9000210f400 EFLAGS: 00000206 RAX: 67e835128c507800 RBX: 0000000000000004 RCX: 67e835128c507800 RDX: 0000000000000006 RSI: ffffffff8d998d6f RDI: ffffffff8be29d80 RBP: ffffc9000210f4b0 R08: ffffffff8fa1f5f7 R09: 1ffffffff1f43ebe R10: dffffc0000000000 R11: fffffbfff1f43ebf R12: 0000000000000212 R13: 1ffff92000421e9c R14: 1ffff92000421e80 R15: dffffc0000000000 blk_mq_raise_softirq block/blk-mq.c:1286 [inline] blk_mq_complete_request_remote+0x6f7/0xa50 block/blk-mq.c:1310 blk_mq_complete_request+0x19/0xa0 block/blk-mq.c:1326 lo_rw_aio_complete drivers/block/loop.c:328 [inline] lo_rw_aio+0xe0b/0x1040 drivers/block/loop.c:402 do_req_filebacked drivers/block/loop.c:-1 [inline] loop_handle_cmd drivers/block/loop.c:1889 [inline] loop_process_work+0x810/0xf40 drivers/block/loop.c:1924 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x711/0x8a0 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 The buggy address ffffc900048ef700 belongs to a vmalloc virtual mapping The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x80331 memcg:ffff8880326fc982 flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff ffff8880326fc982 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 49, tgid 49 (kworker/u8:3), ts 192248198251, free_ts 192190003014 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+0x21e4/0x22c0 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+0x21e/0x870 kernel/fork.c:2599 user_mode_thread+0xdd/0x140 kernel/fork.c:2677 call_usermodehelper_exec_sync kernel/umh.c:132 [inline] call_usermodehelper_exec_work+0x9c/0x230 kernel/umh.c:163 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x711/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 page last free pid 5840 tgid 5840 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1248 [inline] __free_frozen_pages+0xc71/0xe70 mm/page_alloc.c:2706 vfree+0x25a/0x400 mm/vmalloc.c:3434 bch2_fs_btree_write_buffer_exit+0x1ac/0x1e0 fs/bcachefs/btree_write_buffer.c:871 __bch2_fs_free fs/bcachefs/super.c:615 [inline] bch2_fs_release+0x297/0x830 fs/bcachefs/super.c:667 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x22b/0x480 lib/kobject.c:737 deactivate_locked_super+0xbc/0x130 fs/super.c:474 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1417 task_work_run+0x1d4/0x260 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:114 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline] do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffffc900048ef600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffc900048ef680: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 >ffffc900048ef700: 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 00 f2 f2 f2 ^ ffffc900048ef780: 01 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 ffffc900048ef800: 00 00 00 00 f1 f1 f1 f1 00 f3 f3 f3 00 00 00 00 ================================================================== vkms_vblank_simulate: vblank timer overrun ---------------- Code disassembly (best guess): 0: fd std 1: 41 00 48 c7 add %cl,-0x39(%r8) 5: 44 24 20 rex.R and $0x20,%al 8: 00 00 add %al,(%rax) a: 00 00 add %al,(%rax) c: 9c pushf d: 8f 44 24 20 pop 0x20(%rsp) 11: f6 44 24 21 02 testb $0x2,0x21(%rsp) 16: 75 49 jne 0x61 18: 41 f7 c4 00 02 00 00 test $0x200,%r12d 1f: 74 01 je 0x22 21: fb sti 22: 48 c7 04 24 0e 36 e0 movq $0x45e0360e,(%rsp) 29: 45 * 2a: 4b c7 04 3e 00 00 00 movq $0x0,(%r14,%r15,1) <-- trapping instruction 31: 00 32: 66 43 c7 44 3e 09 00 movw $0x0,0x9(%r14,%r15,1) 39: 00 3a: 43 c6 44 3e 0b 00 movb $0x0,0xb(%r14,%r15,1)