loop0: detected capacity change from 0 to 32768
BTRFS: device fsid a6a605fc-d5f1-4e66-8595-3726e2b761d6 devid 1 transid 8 /dev/loop0 (7:0) scanned by syz.0.0 (5359)
BTRFS info (device loop0): first mount of filesystem a6a605fc-d5f1-4e66-8595-3726e2b761d6
BTRFS info (device loop0): using blake2b (blake2b-256-generic) checksum algorithm
BTRFS error (device loop0): failed to load root extent
BTRFS error (device loop0): failed to load root free space
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 0 UID: 0 PID: 5359 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:btrfs_root_node+0x151/0x4a0 fs/btrfs/ctree.c:193
Code: 24 e8 73 43 00 fe c6 05 79 fc cd 0b 01 48 c7 c7 60 29 cd 8b be 4b 03 00 00 48 c7 c2 a0 29 cd 8b e8 c4 0d de fd 48 8b 44 24 18 <42> 80 3c 30 00 74 08 4c 89 e7 e8 f0 2f 65 fe 4d 8b 2c 24 e8 d7 26
RSP: 0018:ffffc9000f507800 EFLAGS: 00010293
RAX: 0000000000000003 RBX: ffffffff83bf774e RCX: ffff888000da8000
RDX: 0000000000000000 RSI: ffffffff8be347e0 RDI: ffffffff8be347a0
RBP: ffffc9000f5078c0 R08: 0000000000000000 R09: ffffffff83bf774e
R10: dffffc0000000000 R11: ffffed100a5bc80e R12: 0000000000000018
R13: ffff88800011c880 R14: dffffc0000000000 R15: 0000000000000001
FS:  00007f133406b6c0(0000) GS:ffff88808d210000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcbfe496f50 CR3: 0000000043f93000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 btrfs_read_lock_root_node+0x27/0xd0 fs/btrfs/locking.c:263
 btrfs_build_ref_tree+0x113/0x1680 fs/btrfs/ref-verify.c:988
 open_ctree+0x2504/0x3a10 fs/btrfs/disk-io.c:3594
 btrfs_fill_super fs/btrfs/super.c:977 [inline]
 btrfs_get_tree_super fs/btrfs/super.c:1940 [inline]
 btrfs_get_tree_subvol fs/btrfs/super.c:2077 [inline]
 btrfs_get_tree+0xf55/0x1820 fs/btrfs/super.c:2111
 vfs_get_tree+0x92/0x2b0 fs/super.c:1815
 do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4324
 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
RIP: 0033:0x7f133319038a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f133406ae68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f133406aef0 RCX: 00007f133319038a
RDX: 0000200000000080 RSI: 0000200000000040 RDI: 00007f133406aeb0
RBP: 0000200000000080 R08: 00007f133406aef0 R09: 000000000201c005
R10: 000000000201c005 R11: 0000000000000246 R12: 0000200000000040
R13: 00007f133406aeb0 R14: 00000000000055cb R15: 0000200000000400
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:btrfs_root_node+0x151/0x4a0 fs/btrfs/ctree.c:193
Code: 24 e8 73 43 00 fe c6 05 79 fc cd 0b 01 48 c7 c7 60 29 cd 8b be 4b 03 00 00 48 c7 c2 a0 29 cd 8b e8 c4 0d de fd 48 8b 44 24 18 <42> 80 3c 30 00 74 08 4c 89 e7 e8 f0 2f 65 fe 4d 8b 2c 24 e8 d7 26
RSP: 0018:ffffc9000f507800 EFLAGS: 00010293
RAX: 0000000000000003 RBX: ffffffff83bf774e RCX: ffff888000da8000
RDX: 0000000000000000 RSI: ffffffff8be347e0 RDI: ffffffff8be347a0
RBP: ffffc9000f5078c0 R08: 0000000000000000 R09: ffffffff83bf774e
R10: dffffc0000000000 R11: ffffed100a5bc80e R12: 0000000000000018
R13: ffff88800011c880 R14: dffffc0000000000 R15: 0000000000000001
FS:  00007f133406b6c0(0000) GS:ffff88808d210000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056452df055f8 CR3: 0000000043f93000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	24 e8                	and    $0xe8,%al
   2:	73 43                	jae    0x47
   4:	00 fe                	add    %bh,%dh
   6:	c6 05 79 fc cd 0b 01 	movb   $0x1,0xbcdfc79(%rip)        # 0xbcdfc86
   d:	48 c7 c7 60 29 cd 8b 	mov    $0xffffffff8bcd2960,%rdi
  14:	be 4b 03 00 00       	mov    $0x34b,%esi
  19:	48 c7 c2 a0 29 cd 8b 	mov    $0xffffffff8bcd29a0,%rdx
  20:	e8 c4 0d de fd       	call   0xfdde0de9
  25:	48 8b 44 24 18       	mov    0x18(%rsp),%rax
* 2a:	42 80 3c 30 00       	cmpb   $0x0,(%rax,%r14,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	4c 89 e7             	mov    %r12,%rdi
  34:	e8 f0 2f 65 fe       	call   0xfe653029
  39:	4d 8b 2c 24          	mov    (%r12),%r13
  3d:	e8                   	.byte 0xe8
  3e:	d7                   	xlat   %ds:(%rbx)
  3f:	26                   	es