Re: kvm: GPF in __get_kvmclock_ns

[Paolo Bonzini]

This one is already known - see "[PATCH] KVM: x86: do not go through vcpu
in __get_kvmclock_ns" which I posted yesterday.

Paolo

----- Original Message -----
> From: "Dmitry Vyukov" <dvyukov@xxxxxxxxxx>
> To: "Paolo Bonzini" <pbonzini@xxxxxxxxxx>, rkrcmar@xxxxxxxxxx, "Thomas Gleixner" <tglx@xxxxxxxxxxxxx>, "Ingo Molnar"
> <mingo@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, x86@xxxxxxxxxx, "KVM list" <kvm@xxxxxxxxxxxxxxx>, "LKML"
> <linux-kernel@xxxxxxxxxxxxxxx>, "Steve Rutherford" <srutherford@xxxxxxxxxx>
> Cc: "syzkaller" <syzkaller@xxxxxxxxxxxxxxxx>
> Sent: Saturday, November 12, 2016 2:21:59 AM
> Subject: Re: kvm: GPF in __get_kvmclock_ns
> 
> On Fri, Nov 11, 2016 at 4:13 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> > Hello,
> >
> > The following program triggers GPF in __get_kvmclock_ns if run in a loop:
> > https://gist.githubusercontent.com/dvyukov/91e4b366019e8500bac73ead5fbc44b0/raw/18178c254775dc953c4b5cf75442207480d939b4/gistfile1.txt
> >
> > On commit 015ed9433be2b476ec7e2e6a9a411a56e3b5b035 (Nov 11).
> >
> > general protection fault: 0000 [#1] SMP KASAN
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Modules linked in:
> > CPU: 3 PID: 4898 Comm: syz-executor Not tainted 4.9.0-rc4+ #40
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
> > 01/01/2011
> > task: ffff880066e32dc0 task.stack: ffff880067280000
> > RIP: 0010:[<ffffffff8108d3be>]  [<ffffffff8108d3be>]
> > __get_kvmclock_ns+0x5e/0x390 arch/x86/kvm/x86.c:1731
> > RSP: 0018:ffff8800672878c0  EFLAGS: 00010003
> > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc90000766000
> > RDX: 000000000000064c RSI: 0000000000000000 RDI: 0000000000003265
> > RBP: ffff8800672878f0 R08: ffffed000ce50f3e R09: ffffed000ce50f3e
> > R10: ffffed000ce50f3d R11: ffff8800672879ef R12: ffff88006728c000
> > R13: ffff88006728c000 R14: 000000002000d000 R15: ffffffffffffffea
> > FS:  00007f0b2288a700(0000) GS:ffff88006e300000(0000)
> > knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 000000002000d000 CR3: 00000000672ba000 CR4: 00000000000026e0
> > Stack:
> >  0000000000000046 1ffff1000ce50f24 1ffff1000ce50f24 ffff8800672879c0
> >  ffff88006728c000 000000002000d000 ffff880067287b90 ffffffff810aafd8
> >  0000000000000038 ffff880067287948 ffffffff812c10f5 1ffff1000ce50f2d
> > Call Trace:
> >  [<ffffffff810aafd8>] kvm_arch_vm_ioctl+0x1098/0x1c10
> >  arch/x86/kvm/x86.c:4096
> >  [<ffffffff81065643>] kvm_vm_ioctl+0x193/0x1670
> > arch/x86/kvm/../../../virt/kvm/kvm_main.c:3097
> >  [<     inline     >] vfs_ioctl fs/ioctl.c:43
> >  [<ffffffff816b16fc>] do_vfs_ioctl+0x18c/0x1040 fs/ioctl.c:679
> >  [<     inline     >] SYSC_ioctl fs/ioctl.c:694
> >  [<ffffffff816b263f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
> >  [<ffffffff831ebd01>] entry_SYSCALL_64_fastpath+0x1f/0xc2
> > Code: 03 80 3c 02 00 0f 85 26 03 00 00 49 8b 9c 24 a0 03 00 00 48 b8
> > 00 00 00 00 00 fc ff df 48 8d bb 65 32 00 00 48 89 fa 48 c1 ea 03 <0f>
> > b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 99 02 00
> > RIP  [<ffffffff8108d3be>] __get_kvmclock_ns+0x5e/0x390
> > arch/x86/kvm/x86.c:1731
> >  RSP <ffff8800672878c0>
> > ---[ end trace 86f1ebae02f87a96 ]---
> > Kernel panic - not syncing: Fatal exception
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Kernel Offset: disabled
> > reboot: cpu_has_vmx: ecx=80a02021 1
> >
> >
> > The line is:
> >     if (vcpu && vcpu->arch.hv_clock.flags & PVCLOCK_TSC_STABLE_BIT) {
> >
> >
> > Thanks
> 
> 
> +Steve
>