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BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
BUG: KASAN: null-ptr-deref in __refcount_sub_and_test include/linux/refcount.h:272 [inline]
BUG: KASAN: null-ptr-deref in __refcount_dec_and_test include/linux/refcount.h:315 [inline]
BUG: KASAN: null-ptr-deref in refcount_dec_and_test include/linux/refcount.h:333 [inline]
BUG: KASAN: null-ptr-deref in kref_put include/linux/kref.h:64 [inline]
BUG: KASAN: null-ptr-deref in bdi_put+0x22/0xa0 mm/backing-dev.c:901
Write of size 4 at addr 0000000000000040 by task syz-executor.0/10438

CPU: 3 PID: 10438 Comm: syz-executor.0 Not tainted 5.11.0-rc1-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 __kasan_report mm/kasan/report.c:400 [inline]
 kasan_report.cold+0x5f/0xd5 mm/kasan/report.c:413
 check_memory_region_inline mm/kasan/generic.c:179 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:185
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
 __refcount_sub_and_test include/linux/refcount.h:272 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 kref_put include/linux/kref.h:64 [inline]
 bdi_put+0x22/0xa0 mm/backing-dev.c:901
 bdev_evict_inode+0x262/0x460 fs/block_dev.c:808
 evict+0x2ed/0x6b0 fs/inode.c:577
 iput_final fs/inode.c:1653 [inline]
 iput.part.0+0x57e/0x810 fs/inode.c:1679
 iput+0x58/0x70 fs/inode.c:1669
 dentry_unlink_inode+0x2b1/0x3d0 fs/dcache.c:374
 __dentry_kill+0x3c0/0x640 fs/dcache.c:579
 dentry_kill fs/dcache.c:705 [inline]
 dput+0x725/0xbc0 fs/dcache.c:885
 do_one_tree fs/dcache.c:1632 [inline]
 shrink_dcache_for_umount+0x11f/0x330 fs/dcache.c:1646
 generic_shutdown_super+0x68/0x370 fs/super.c:447
 kill_anon_super+0x36/0x60 fs/super.c:1055
 deactivate_locked_super+0x94/0x160 fs/super.c:335
 deactivate_super+0xad/0xd0 fs/super.c:366
 put_fs_context+0xaa/0x650 fs/fs_context.c:442
 fscontext_release+0x4c/0x60 fs/fsopen.c:73
 __fput+0x283/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x190 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
 __do_fast_syscall_32+0x62/0x80 arch/x86/entry/common.c:138
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7f5d549
Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000fff71a7c EFLAGS: 00000293 ORIG_RAX: 0000000000000006
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 000000000815f000 RSI: 0000000000000004 RDI: 000000000815f000
RBP: 0000000008190120 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
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