Re: [syzbot] [kvm?] [net?] [virt?] general protection fault in vhost_work_queue

[Stefano Garzarella]

On Tue, May 30, 2023 at 1:24 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Tue, May 30, 2023 at 12:30:06AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    933174ae28ba Merge tag 'spi-fix-v6.4-rc3' of git://git.ker..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=138d4ae5280000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=f389ffdf4e9ba3f0
> > dashboard link: https://syzkaller.appspot.com/bug?extid=d0d442c22fa8db45ff0e
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/21a81b8c2660/disk-933174ae.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/b4951d89e238/vmlinux-933174ae.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/21eb405303cc/bzImage-933174ae.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+d0d442c22fa8db45ff0e@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] PREEMPT SMP KASAN
> > KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
> > CPU: 0 PID: 29845 Comm: syz-executor.4 Not tainted 6.4.0-rc3-syzkaller-00032-g933174ae28ba #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/16/2023
> > RIP: 0010:vhost_work_queue drivers/vhost/vhost.c:259 [inline]
> > RIP: 0010:vhost_work_queue+0xfc/0x150 drivers/vhost/vhost.c:248
> > Code: 00 00 fc ff df 48 89 da 48 c1 ea 03 80 3c 02 00 75 56 48 b8 00 00 00 00 00 fc ff df 48 8b 1b 48 8d 7b 70 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 42 48 8b 7b 70 e8 95 9e ae f9 5b 5d 41 5c 41 5d e9
> > RSP: 0018:ffffc9000333faf8 EFLAGS: 00010202
> > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000d84d000
> > RDX: 000000000000000e RSI: ffffffff841221d7 RDI: 0000000000000070
> > RBP: ffff88804b6b95b0 R08: 0000000000000001 R09: 0000000000000000
> > R10: 0000000000000001 R11: 0000000000000000 R12: ffff88804b6b00b0
> > R13: 0000000000000000 R14: ffff88804b6b95e0 R15: ffff88804b6b95c8
> > FS:  00007f3b445ec700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000001b2e423000 CR3: 000000005d734000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 000000000000003b DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > Call Trace:
> >  <TASK>
> >  vhost_transport_send_pkt+0x268/0x520 drivers/vhost/vsock.c:288
> >  virtio_transport_send_pkt_info+0x54c/0x820 net/vmw_vsock/virtio_transport_common.c:250
> >  virtio_transport_connect+0xb1/0xf0 net/vmw_vsock/virtio_transport_common.c:813
> >  vsock_connect+0x37f/0xcd0 net/vmw_vsock/af_vsock.c:1414
> >  __sys_connect_file+0x153/0x1a0 net/socket.c:2003
> >  __sys_connect+0x165/0x1a0 net/socket.c:2020
> >  __do_sys_connect net/socket.c:2030 [inline]
> >  __se_sys_connect net/socket.c:2027 [inline]
> >  __x64_sys_connect+0x73/0xb0 net/socket.c:2027
> >  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: 0033:0x7f3b4388c169
> > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007f3b445ec168 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
> > RAX: ffffffffffffffda RBX: 00007f3b439ac050 RCX: 00007f3b4388c169
> > RDX: 0000000000000010 RSI: 0000000020000140 RDI: 0000000000000004
> > RBP: 00007f3b438e7ca1 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > R13: 00007f3b43acfb1f R14: 00007f3b445ec300 R15: 0000000000022000
> >  </TASK>
> > Modules linked in:
> > ---[ end trace 0000000000000000 ]---
> > RIP: 0010:vhost_work_queue drivers/vhost/vhost.c:259 [inline]
> > RIP: 0010:vhost_work_queue+0xfc/0x150 drivers/vhost/vhost.c:248
> > Code: 00 00 fc ff df 48 89 da 48 c1 ea 03 80 3c 02 00 75 56 48 b8 00 00 00 00 00 fc ff df 48 8b 1b 48 8d 7b 70 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 42 48 8b 7b 70 e8 95 9e ae f9 5b 5d 41 5c 41 5d e9
> > RSP: 0018:ffffc9000333faf8 EFLAGS: 00010202
> > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000d84d000
> > RDX: 000000000000000e RSI: ffffffff841221d7 RDI: 0000000000000070
> > RBP: ffff88804b6b95b0 R08: 0000000000000001 R09: 0000000000000000
> > R10: 0000000000000001 R11: 0000000000000000 R12: ffff88804b6b00b0
> > R13: 0000000000000000 R14: ffff88804b6b95e0 R15: ffff88804b6b95c8
> > FS:  00007f3b445ec700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000001b2e428000 CR3: 000000005d734000 CR4: 00000000003506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 000000000000003b DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > ----------------
> > Code disassembly (best guess), 5 bytes skipped:
> >    0: 48 89 da                mov    %rbx,%rdx
> >    3: 48 c1 ea 03             shr    $0x3,%rdx
> >    7: 80 3c 02 00             cmpb   $0x0,(%rdx,%rax,1)
> >    b: 75 56                   jne    0x63
> >    d: 48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
> >   14: fc ff df
> >   17: 48 8b 1b                mov    (%rbx),%rbx
> >   1a: 48 8d 7b 70             lea    0x70(%rbx),%rdi
> >   1e: 48 89 fa                mov    %rdi,%rdx
> >   21: 48 c1 ea 03             shr    $0x3,%rdx
> > * 25: 80 3c 02 00             cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
> >   29: 75 42                   jne    0x6d
> >   2b: 48 8b 7b 70             mov    0x70(%rbx),%rdi
> >   2f: e8 95 9e ae f9          callq  0xf9ae9ec9
> >   34: 5b                      pop    %rbx
> >   35: 5d                      pop    %rbp
> >   36: 41 5c                   pop    %r12
> >   38: 41 5d                   pop    %r13
> >   3a: e9                      .byte 0xe9
>
>
> Stefano, Stefan, take a look?

I'll take a look.

>From a first glance, it looks like an issue when we call vhost_work_queue().
@Mike, does that ring any bells since you recently looked at that code?

Thanks,
Stefano