[syzbot] [block?] general protection fault in start_motor (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    2ccdd1b13c59 Linux 6.5-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138ad837a80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8fc59e2140295873
dashboard link: https://syzkaller.appspot.com/bug?extid=1fad709a9a55674f0e0b
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=101c2b69a80000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-2ccdd1b1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/421f85ee78b3/vmlinux-2ccdd1b1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a52df43998f1/bzImage-2ccdd1b1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1fad709a9a55674f0e0b@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: 0 PID: 12 Comm: kworker/u16:1 Not tainted 6.5.0-rc6-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: floppy floppy_work_workfn
RIP: 0010:start_motor+0x3a/0x3e0 drivers/block/floppy.c:1905
Code: 08 e8 da 6d 50 fc 48 8b 1d 73 8c 0d 0d 48 b8 00 00 00 00 00 fc ff df 0f b6 2d c2 76 0d 0d 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 a8 02 00
RSP: 0018:ffffc90000317c70 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8534b2e6 RDI: ffffffff8534e840
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8534e840
R13: 0000000000000001 R14: ffff88801cfc5000 R15: ffffffff8d6dffe0
FS:  0000000000000000(0000) GS:ffff88806b600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2f4f471c98 CR3: 00000000222a8000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 floppy_ready+0x87/0x1b40 drivers/block/floppy.c:1932
 process_one_work+0xaa2/0x16f0 kernel/workqueue.c:2600
 worker_thread+0x687/0x1110 kernel/workqueue.c:2751
 kthread+0x33a/0x430 kernel/kthread.c:389
 ret_from_fork+0x2c/0x70 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:start_motor+0x3a/0x3e0 drivers/block/floppy.c:1905
Code: 08 e8 da 6d 50 fc 48 8b 1d 73 8c 0d 0d 48 b8 00 00 00 00 00 fc ff df 0f b6 2d c2 76 0d 0d 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 a8 02 00
RSP: 0018:ffffc90000317c70 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8534b2e6 RDI: ffffffff8534e840
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8534e840
R13: 0000000000000001 R14: ffff88801cfc5000 R15: ffffffff8d6dffe0
FS:  0000000000000000(0000) GS:ffff88806b600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2f4f471c98 CR3: 00000000222a8000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	08 e8                	or     %ch,%al
   2:	da 6d 50             	fisubrl 0x50(%rbp)
   5:	fc                   	cld
   6:	48 8b 1d 73 8c 0d 0d 	mov    0xd0d8c73(%rip),%rbx        # 0xd0d8c80
   d:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  14:	fc ff df
  17:	0f b6 2d c2 76 0d 0d 	movzbl 0xd0d76c2(%rip),%ebp        # 0xd0d76e0
  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:	a8 02                	test   $0x2,%al


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