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BUG: KASAN: use-after-free in btrfs_printk+0x38b/0x40c fs/btrfs/super.c:245
Read of size 8 at addr ffff8880125506a0 by task systemd-udevd/12463

CPU: 1 PID: 12463 Comm: systemd-udevd Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
 btrfs_printk+0x38b/0x40c fs/btrfs/super.c:245
 device_list_add.cold+0x99/0x31e fs/btrfs/volumes.c:943
 btrfs_scan_one_device+0x339/0x4a0 fs/btrfs/volumes.c:1354
 btrfs_control_ioctl+0x12a/0x2d0 fs/btrfs/super.c:2327
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f34d55ed017
Code: 00 00 00 48 8b 05 81 7e 2b 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 51 7e 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd147141d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f34d55ed017
RDX: 00007ffd147141f0 RSI: 0000000090009427 RDI: 000000000000000f
RBP: 00007ffd147141f0 R08: 0000000000000000 R09: 00000000000000d8
R10: 0000000000000001 R11: 0000000000000246 R12: 000000000000000f
R13: 0000000000000000 R14: 000055b5303ec480 R15: 000055b5303ec100

The buggy address belongs to the page:
page:000000001067dec5 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x12550
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea00007c9308 ffffea000075a308 0000000000000000
raw: 0000000000000000 0000000000000002 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888012550580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888012550600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888012550680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff888012550700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888012550780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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