Re: [syzbot] general protection fault in gfs2_get_tree

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    591cd61541b9 Add linux-next specific files for 20221207
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10edd843880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8b2d3e63e054c24f
dashboard link: https://syzkaller.appspot.com/bug?extid=2be9d17f9de2e7342994
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10dfde7d880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bc862c01ec56/disk-591cd615.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8f9b93f8ed2f/vmlinux-591cd615.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9d5cb636d548/bzImage-591cd615.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/d4c744809640/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2be9d17f9de2e7342994@xxxxxxxxxxxxxxxxxxxxxxxxx

loop1: detected capacity change from 0 to 32768
general protection fault, probably for non-canonical address 0xdffffc000000001c: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000e0-0x00000000000000e7]
CPU: 1 PID: 5330 Comm: syz-executor.1 Not tainted 6.1.0-rc8-next-20221207-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:gfs2_get_tree+0xb8/0x270 fs/gfs2/ops_fstype.c:1342
Code: 03 80 3c 02 00 0f 85 9f 01 00 00 4c 8b bb b0 00 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bf e0 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 62 01 00 00 4d 8b b7 e0 00 00 00 48 b8 00 00 00
RSP: 0018:ffffc900049a7d50 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88802319c000 RCX: 0000000000000000
RDX: 000000000000001c RSI: ffffffff83925ec7 RDI: 00000000000000e0
RBP: ffff88807bed3800 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000094001 R12: 0000000000000000
R13: ffff88802319c0b0 R14: ffff88802319c000 R15: 0000000000000000
FS:  00007f687e332700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27ec317000 CR3: 0000000021f43000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 vfs_get_tree+0x8d/0x2f0 fs/super.c:1489
 do_new_mount fs/namespace.c:3145 [inline]
 path_mount+0x132a/0x1e20 fs/namespace.c:3475
 do_mount fs/namespace.c:3488 [inline]
 __do_sys_mount fs/namespace.c:3697 [inline]
 __se_sys_mount fs/namespace.c:3674 [inline]
 __x64_sys_mount+0x283/0x300 fs/namespace.c:3674
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f687d68d60a
Code: 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 b8 04 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f687e331f88 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00000000000133e6 RCX: 00007f687d68d60a
RDX: 0000000020013400 RSI: 0000000020013440 RDI: 00007f687e331fe0
RBP: 00007f687e332020 R08: 00007f687e332020 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020013400
R13: 0000000020013440 R14: 00007f687e331fe0 R15: 00000000200000c0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:gfs2_get_tree+0xb8/0x270 fs/gfs2/ops_fstype.c:1342
Code: 03 80 3c 02 00 0f 85 9f 01 00 00 4c 8b bb b0 00 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bf e0 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 62 01 00 00 4d 8b b7 e0 00 00 00 48 b8 00 00 00
RSP: 0018:ffffc900049a7d50 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88802319c000 RCX: 0000000000000000
RDX: 000000000000001c RSI: ffffffff83925ec7 RDI: 00000000000000e0
RBP: ffff88807bed3800 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000094001 R12: 0000000000000000
R13: ffff88802319c0b0 R14: ffff88802319c000 R15: 0000000000000000
FS:  00007f687e332700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe54d4e8000 CR3: 0000000021f43000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	03 80 3c 02 00 0f    	add    0xf00023c(%rax),%eax
   6:	85 9f 01 00 00 4c    	test   %ebx,0x4c000001(%rdi)
   c:	8b bb b0 00 00 00    	mov    0xb0(%rbx),%edi
  12:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  19:	fc ff df
  1c:	49 8d bf e0 00 00 00 	lea    0xe0(%r15),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 62 01 00 00    	jne    0x196
  34:	4d 8b b7 e0 00 00 00 	mov    0xe0(%r15),%r14
  3b:	48                   	rex.W
  3c:	b8                   	.byte 0xb8
  3d:	00 00                	add    %al,(%rax)