[syzbot] general protection fault in start_motor (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    10d4879f9ef0 Merge tag 'thermal-6.0-rc3' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=116400e5080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=312be25752c7fe30
dashboard link: https://syzkaller.appspot.com/bug?extid=30e9df1b3f1d5117d77f
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=126b8675080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+30e9df1b3f1d5117d77f@xxxxxxxxxxxxxxxxxxxxxxxxx

floppy1: FDC access conflict!
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 12 Comm: kworker/u16:1 Not tainted 6.0.0-rc2-syzkaller-00283-g10d4879f9ef0 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Workqueue: floppy floppy_work_workfn
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 7a 39 e0 fc 48 8b 1d 63 54 ae 0c 48 b8 00 00 00 00 00 fc ff df 0f b6 2d b2 3e ae 0c 48 89 da 48 c1 ea 03 89 e9 41 89 ed <0f> b6 04 02 83 e1 03 41 83 e5 03 84 c0 74 08 3c 03 0f 8e be 02 00
RSP: 0018:ffffc900005ffc98 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff849b0096 RDI: ffffffff849b2f00
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff849b2f00
R13: 0000000000000001 R14: ffff888012459400 R15: ffff888011875800
FS:  0000000000000000(0000) GS:ffff88802c900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0afb5ff718 CR3: 000000001b6a0000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 floppy_ready+0x83/0x1940 drivers/block/floppy.c:1932
 process_one_work+0x991/0x1610 kernel/workqueue.c:2289
 worker_thread+0x665/0x1080 kernel/workqueue.c:2436
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 7a 39 e0 fc 48 8b 1d 63 54 ae 0c 48 b8 00 00 00 00 00 fc ff df 0f b6 2d b2 3e ae 0c 48 89 da 48 c1 ea 03 89 e9 41 89 ed <0f> b6 04 02 83 e1 03 41 83 e5 03 84 c0 74 08 3c 03 0f 8e be 02 00
RSP: 0018:ffffc900005ffc98 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff849b0096 RDI: ffffffff849b2f00
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff849b2f00
R13: 0000000000000001 R14: ffff888012459400 R15: ffff888011875800
FS:  0000000000000000(0000) GS:ffff88802c900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0afb5ff718 CR3: 00000000284ad000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	08 e8                	or     %ch,%al
   2:	7a 39                	jp     0x3d
   4:	e0 fc                	loopne 0x2
   6:	48 8b 1d 63 54 ae 0c 	mov    0xcae5463(%rip),%rbx        # 0xcae5470
   d:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  14:	fc ff df
  17:	0f b6 2d b2 3e ae 0c 	movzbl 0xcae3eb2(%rip),%ebp        # 0xcae3ed0
  1e:	48 89 da             	mov    %rbx,%rdx
  21:	48 c1 ea 03          	shr    $0x3,%rdx
  25:	89 e9                	mov    %ebp,%ecx
  27:	41 89 ed             	mov    %ebp,%r13d
* 2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e:	83 e1 03             	and    $0x3,%ecx
  31:	41 83 e5 03          	and    $0x3,%r13d
  35:	84 c0                	test   %al,%al
  37:	74 08                	je     0x41
  39:	3c 03                	cmp    $0x3,%al
  3b:	0f                   	.byte 0xf
  3c:	8e                   	.byte 0x8e
  3d:	be                   	.byte 0xbe
  3e:	02 00                	add    (%rax),%al


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