Re: general protection fault in kvm_coalesced_mmio_init

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    00aff683 Merge tag 'for-5.4-rc6-tag' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1777fb52e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=896c87b73c6fcda6
dashboard link: https://syzkaller.appspot.com/bug?extid=e27e7027eb2b80e44225
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17ed65aae00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e27e7027eb2b80e44225@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 20263 Comm: syz-executor.2 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:kvm_coalesced_mmio_init+0x59/0xf0  
arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:121
Code: 00 00 00 fc ff df e8 46 7d 6b 00 48 c1 e3 06 49 be 00 00 00 00 80 08  
05 00 49 01 de 49 8d bf d8 96 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00  
74 05 e8 bb bb a4 00 4d 89 b7 d8 96 00 00 49 8d bf
RSP: 0018:ffff888091647d10 EFLAGS: 00010206
RAX: 00000000000012db RBX: fffa80009cb1b000 RCX: ffff8880a42d21c0
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 00000000000096d8
RBP: ffff888091647d30 R08: ffffffff83486eda R09: ffffed1015d46b05
R10: ffffed1015d46b05 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88809cb1b000 R15: 0000000000000000
FS:  00007fb51eb61700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa986fb7000 CR3: 000000009c69d000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:3448  
[inline]
 kvm_dev_ioctl+0x18fa/0x1fd0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3496
 do_vfs_ioctl+0x744/0x1730 fs/ioctl.c:46
 ksys_ioctl fs/ioctl.c:713 [inline]
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0xe3/0x120 fs/ioctl.c:718
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a219
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb51eb60c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a219
RDX: 0000000000000000 RSI: 000000000000ae01 RDI: 0000000000000004
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb51eb616d4
R13: 00000000004c348b R14: 00000000004d7708 R15: 00000000ffffffff
Modules linked in:
---[ end trace 15ab0f35a80c9e5d ]---
RIP: 0010:kvm_coalesced_mmio_init+0x59/0xf0  
arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:121
Code: 00 00 00 fc ff df e8 46 7d 6b 00 48 c1 e3 06 49 be 00 00 00 00 80 08  
05 00 49 01 de 49 8d bf d8 96 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00  
74 05 e8 bb bb a4 00 4d 89 b7 d8 96 00 00 49 8d bf
RSP: 0018:ffff888091647d10 EFLAGS: 00010206
RAX: 00000000000012db RBX: fffa80009cb1b000 RCX: ffff8880a42d21c0
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 00000000000096d8
RBP: ffff888091647d30 R08: ffffffff83486eda R09: ffffed1015d46b05
R10: ffffed1015d46b05 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88809cb1b000 R15: 0000000000000000
FS:  00007fb51eb61700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 000000009c69d000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400