qnx6: unable to read the first superblock
------------[ cut here ]------------
WARNING: CPU: 0 PID: 30978 at fs/buffer.c:1125 __getblk_slow+0x4cc/0x560 fs/buffer.c:1125
Modules linked in:
CPU: 0 UID: 0 PID: 30978 Comm: syz.8.6356 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:__getblk_slow+0x4cc/0x560 fs/buffer.c:1125
Code: 80 8b 48 89 df e8 04 08 bb ff 90 0f 0b e8 ec f7 71 ff 48 c7 c6 a0 83 80 8b 48 89 df e8 ed 07 bb ff 90 0f 0b e8 d5 f7 71 ff 90 <0f> 0b 90 8b 74 24 0c 89 ea 48 c7 c7 00 85 80 8b 31 db e8 8d b2 50
RSP: 0018:ffffc90003a0fa68 EFLAGS: 00010287
RAX: 0000000000002b9c RBX: 0000000000000200 RCX: ffffc9000d872000
RDX: 0000000000080000 RSI: ffffffff8248ad8b RDI: 0000000000000005
RBP: 0000000000000400 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000200 R11: 0000000000000000 R12: ffff88801dbf8000
R13: 0000000000000000 R14: 0000000000000200 R15: ffff88801dbf8000
FS:  0000000000000000(0000) GS:ffff888097c8c000(0063) knlGS:00000000f5465b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f5465da4 CR3: 00000000710de000 CR4: 0000000000352ef0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 bdev_getblk+0xd4/0xe0 fs/buffer.c:1461
 __bread_gfp+0x86/0x3c0 fs/buffer.c:1515
 sb_bread include/linux/buffer_head.h:346 [inline]
 qnx6_check_first_superblock+0xab/0x2d0 fs/qnx6/inode.c:260
 qnx6_fill_super+0xd8d/0x1520 fs/qnx6/inode.c:332
 get_tree_bdev_flags+0x38c/0x620 fs/super.c:1692
 vfs_get_tree+0x8e/0x340 fs/super.c:1752
 do_new_mount fs/namespace.c:3750 [inline]
 path_mount+0x1516/0x2060 fs/namespace.c:4065
 do_mount fs/namespace.c:4078 [inline]
 __do_sys_mount fs/namespace.c:4278 [inline]
 __se_sys_mount fs/namespace.c:4255 [inline]
 __ia32_sys_mount+0x28b/0x310 fs/namespace.c:4255
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x7c/0x300 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:331
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7f93579
Code: 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 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f546555c EFLAGS: 00000296 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 0000000080000000 RCX: 0000000080004a00
RDX: 0000000080000040 RSI: 0000000002008087 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	10 06                	adc    %al,(%rsi)
   2:	03 74 b4 01          	add    0x1(%rsp,%rsi,4),%esi
   6:	10 07                	adc    %al,(%rdi)
   8:	03 74 b0 01          	add    0x1(%rax,%rsi,4),%esi
   c:	10 08                	adc    %cl,(%rax)
   e:	03 74 d8 01          	add    0x1(%rax,%rbx,8),%esi
  1e:	00 51 52             	add    %dl,0x52(%rcx)
  21:	55                   	push   %rbp
  22:	89 e5                	mov    %esp,%ebp
  24:	0f 34                	sysenter
  26:	cd 80                	int    $0x80
* 28:	5d                   	pop    %rbp <-- trapping instruction
  29:	5a                   	pop    %rdx
  2a:	59                   	pop    %rcx
  2b:	c3                   	ret
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	90                   	nop
  2f:	90                   	nop
  30:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
  37:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi