Hi,
We would like to report the following bug which has been found by our
modified version of syzkaller.
======================================================
description: general protection fault in start_motor
affected file: drivers/block/floppy.c
kernel version: 5.10.131
kernel commit: de62055f423f5dcb548f74cebd68f03c8903f73a
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=e49433cfed49b7d9
crash reproducer: attached
======================================================
Crash log:
======================================================
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: 8820 Comm: kworker/u4:48 Tainted: G OE 5.10.131+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Workqueue: floppy fd_timer_workfn
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 4a 15 1c fd 48 8b 1d 03 30 4d 0b 48 b8 00 00 00 00 00 fc
ff df 0f b6 2d 72 22 4d 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:ffffc90000a47cc0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff845483d6 RDI: ffffffff84549f90
RBP: 0000000000000000 R08: ffff88803a2b1ac0 R09: fffffbfff19dad22
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84549f90
R13: 0000000000000000 R14: ffff88810c148000 R15: ffff888100069800
FS: 0000000000000000(0000) GS:ffff88811a000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fb22000 CR3: 000000002daa9001 CR4: 0000000000170ef0
Call Trace:
floppy_ready+0x7f/0x1950 drivers/block/floppy.c:1932
process_one_work+0x953/0x15c0 kernel/workqueue.c:2279
worker_thread+0x96/0xe20 kernel/workqueue.c:2425
kthread+0x374/0x490 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Modules linked in: uio_ivshmem(OE) uio(E)
---[ end trace 345300e45e5eb538 ]---
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 4a 15 1c fd 48 8b 1d 03 30 4d 0b 48 b8 00 00 00 00 00 fc
ff df 0f b6 2d 72 22 4d 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:ffffc90000a47cc0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff845483d6 RDI: ffffffff84549f90
RBP: 0000000000000000 R08: ffff88803a2b1ac0 R09: fffffbfff19dad22
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84549f90
R13: 0000000000000000 R14: ffff88810c148000 R15: ffff888100069800
FS: 0000000000000000(0000) GS:ffff88811a000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fee2b352038 CR3: 00000000425db005 CR4: 0000000000170ef0
----------------
Code disassembly (best guess):
0: 08 e8 or %ch,%al
2: 4a 15 1c fd 48 8b rex.WX adc $0xffffffff8b48fd1c,%rax
8: 1d 03 30 4d 0b sbb $0xb4d3003,%eax
d: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
14: fc ff df
17: 0f b6 2d 72 22 4d 0b movzbl 0xb4d2272(%rip),%ebp # 0xb4d2290
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
--
Thanks and Regards,
Dipanjan