qnx6: unable to read the first superblock
------------[ cut here ]------------
WARNING: CPU: 0 PID: 5318 at fs/buffer.c:1125 __getblk_slow fs/buffer.c:1125 [inline]
WARNING: CPU: 0 PID: 5318 at fs/buffer.c:1125 bdev_getblk+0x580/0x660 fs/buffer.c:1461
Modules linked in:
CPU: 0 UID: 0 PID: 5318 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:__getblk_slow fs/buffer.c:1125 [inline]
RIP: 0010:bdev_getblk+0x580/0x660 fs/buffer.c:1461
Code: 26 fb ff ff e8 e1 9e 75 ff 48 c7 c7 20 27 7a 8b 48 c7 c6 3e 01 76 8d 4c 89 fa 4c 89 e9 e8 18 1d dd fe eb bd e8 c1 9e 75 ff 90 <0f> 0b 90 48 b8 00 00 00 00 00 fc ff df 41 80 3c 07 00 74 08 48 89
RSP: 0018:ffffc9000d43f9d8 EFLAGS: 00010287
RAX: ffffffff824a74cf RBX: ffff8880008c5098 RCX: 0000000000100000
RDX: ffffc9000e7db000 RSI: 0000000000002321 RDI: 0000000000002322
RBP: 0000000000000200 R08: 0000000000000000 R09: ffffffff82195fbd
R10: 0000000000000406 R11: 0000000000000002 R12: ffff8880008c59f0
R13: ffff8880008c5080 R14: 0000000000000200 R15: 1ffff11000118a13
FS:  00007f61d6a8c6c0(0000) GS:ffff88808d733000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcf200fad8 CR3: 00000000415e0000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __bread_gfp+0x89/0x3c0 fs/buffer.c:1515
 sb_bread include/linux/buffer_head.h:346 [inline]
 qnx6_check_first_superblock+0xa1/0x330 fs/qnx6/inode.c:260
 qnx6_fill_super+0x4c8/0x1280 fs/qnx6/inode.c:332
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
 vfs_get_tree+0x92/0x2b0 fs/super.c:1751
 fc_mount fs/namespace.c:1208 [inline]
 do_new_mount_fc fs/namespace.c:3651 [inline]
 do_new_mount+0x302/0xa10 fs/namespace.c:3727
 do_mount fs/namespace.c:4050 [inline]
 __do_sys_mount fs/namespace.c:4238 [inline]
 __se_sys_mount+0x313/0x410 fs/namespace.c:4215
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f61d5b8efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007f61d6a8c038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f61d5de6090 RCX: 00007f61d5b8efc9
RDX: 0000200000000000 RSI: 00002000000002c0 RDI: 0000200000000100
RBP: 00007f61d5c11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f61d5de6128 R14: 00007f61d5de6090 R15: 00007fff9ca6c708
 </TASK>