[syzbot] general protection fault in start_motor

syzbot
2021-10-21T14:07:33Z

Hello,

syzbot found the following issue on:

HEAD commit: d999ade1cc86 Merge tag 'perf-tools-fixes-for-v5.15-2021-10..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146197f4b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=bab9d35f204746a7
dashboard link: https://syzkaller.appspot.com/bug?extid=4e9b2677f1f8fba5cb18
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e9b2677f1f8fba5cb18@syzkaller.appspotmail.com

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: 3 PID: 3980 Comm: kworker/u16:5 Not tainted 5.15.0-rc5-syzkaller #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 6a 52 05 fd 48 8b 1d 73 38 e1 0b 48 b8 00 00 00 00 00 fc ff df 0f b6 2d 82 22 e1 0b 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:ffffc90007e3fca8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff847185a6 RDI: ffffffff8471c2e0
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff8471c346 R11: 0000000000000000 R12: ffffffff8471c2e0
R13: 0000000000000001 R14: ffff8880129da500 R15: ffff888010c71800
FS: 0000000000000000(0000) GS:ffff88802cd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000049291000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
floppy_ready+0x7f/0x1930 drivers/block/floppy.c:1932
process_one_work+0x9bf/0x16b0 kernel/workqueue.c:2297
worker_thread+0x658/0x11f0 kernel/workqueue.c:2444
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Modules linked in:
---[ end trace 5ab26389b77b524a ]---
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 6a 52 05 fd 48 8b 1d 73 38 e1 0b 48 b8 00 00 00 00 00 fc ff df 0f b6 2d 82 22 e1 0b 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:ffffc90007e3fca8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff847185a6 RDI: ffffffff8471c2e0
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff8471c346 R11: 0000000000000000 R12: ffffffff8471c2e0
R13: 0000000000000001 R14: ffff8880129da500 R15: ffff888010c71800
FS: 0000000000000000(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002001d000 CR3: 000000000b68e000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 08 e8 or %ch,%al
2: 6a 52 pushq $0x52
4: 05 fd 48 8b 1d add $0x1d8b48fd,%eax
9: 73 38 jae 0x43
b: e1 0b loope 0x18
d: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
14: fc ff df
17: 0f b6 2d 82 22 e1 0b movzbl 0xbe12282(%rip),%ebp # 0xbe122a0
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

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.