linux-kernel - BUG: unable to handle kernel NULL pointer dereference in kvm_vm_worker

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Message-ID: <0000000000005d5b5905aec85912@google.com>
Date:   Tue, 08 Sep 2020 00:33:19 -0700
From:   syzbot <syzbot+e4a6c438918d1db4e4fc@...kaller.appspotmail.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, syzkaller-bugs@...glegroups.com
Subject: BUG: unable to handle kernel NULL pointer dereference in kvm_vm_worker_thread

Hello,

syzbot found the following issue on:

HEAD commit:    15bc20c6 Merge tag 'tty-5.9-rc3' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15d432fe900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=978db74cb30aa994
dashboard link: https://syzkaller.appspot.com/bug?extid=e4a6c438918d1db4e4fc
compiler:       gcc (GCC) 10.1.0-syz 20200507

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+e4a6c438918d1db4e4fc@...kaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 5d428067 P4D 5d428067 PUD 5d429067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7418 Comm: kvm-nx-lpage-re Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:kvm_vm_worker_thread+0xe9/0x270 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4912
Code: 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 37 01 00 00 48 8b 7b 08 4c 89 ee e8 23 99 67 00 31 ff 41 89 c4 89 c6 e8 a7 4b 6d 00 <00> 00 00 0f 85 97 31 02 00 e8 19 4f 6d 00 48 8b 54 24 08 48 b8 00
RSP: 0018:ffffc90012097ed0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffc90011e87cf8 RCX: ffffffff8106efe9
RDX: 0000000000000000 RSI: ffff88804c02e040 RDI: 0000000000000005
RBP: ffffc90011e87d08 R08: 0000000000000001 R09: ffffffff89bfd407
R10: 0000000000000000 R11: 0000000000000160 R12: 0000000000000000
R13: ffff88804c02e040 R14: ffffc90012081000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000005d427000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Modules linked in:
CR2: 0000000000000000
---[ end trace 7a7affa1f4a7d557 ]---
RIP: 0010:kvm_vm_worker_thread+0xe9/0x270 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4912
Code: 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 37 01 00 00 48 8b 7b 08 4c 89 ee e8 23 99 67 00 31 ff 41 89 c4 89 c6 e8 a7 4b 6d 00 <00> 00 00 0f 85 97 31 02 00 e8 19 4f 6d 00 48 8b 54 24 08 48 b8 00
RSP: 0018:ffffc90012097ed0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffc90011e87cf8 RCX: ffffffff8106efe9
RDX: 0000000000000000 RSI: ffff88804c02e040 RDI: 0000000000000005
RBP: ffffc90011e87d08 R08: 0000000000000001 R09: ffffffff89bfd407
R10: 0000000000000000 R11: 0000000000000160 R12: 0000000000000000
R13: ffff88804c02e040 R14: ffffc90012081000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000005d427000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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