linux-kernel - Re: kvm: WARNING in kvm_load_guest

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Date:   Sun, 22 Jan 2017 09:45:25 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>, KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Steve Rutherford <srutherford@...gle.com>
Cc:     syzkaller <syzkaller@...glegroups.com>
Subject: Re: kvm: WARNING in kvm_load_guest_fpu

On Sat, Nov 12, 2016 at 4:57 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> Hello,
>
> The following program triggers WARNING in kvm_load_guest_fpu:
> https://gist.githubusercontent.com/dvyukov/5bc076073b48772e22b5f33acbe2b743/raw/1000df869f0d58a5c6e637268453c711280b255d/gistfile1.txt
>
> On commit 015ed9433be2b476ec7e2e6a9a411a56e3b5b035 (Nov 11).
>
> WARNING: CPU: 3 PID: 23924 at
> ./arch/x86/include/asm/fpu/internal.h:164
> kvm_load_guest_fpu.part.163+0xf1/0x340
> Kernel panic - not syncing: panic_on_warn set ...
>
> CPU: 3 PID: 23924 Comm: syz-executor Not tainted 4.9.0-rc4+ #44
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  ffff88006ce67920 ffffffff81c2f79b ffffffff83271fc0 ffff88006ce679f8
>  ffffffff8321c300 ffffffff81096631 ffff88006ce679e8 ffffffff81548463
>  0000000041b58ab3 ffffffff837cd505 ffffffff815482ac ffffffff815490e9
> Call Trace:
>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>  [<ffffffff81c2f79b>] dump_stack+0xb3/0x118 lib/dump_stack.c:51
>  [<ffffffff81548463>] panic+0x1b7/0x3a3 kernel/panic.c:179
>  [<ffffffff81240014>] __warn+0x1c4/0x1e0 kernel/panic.c:542
>  [<ffffffff812401fc>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
>  [<     inline     >] copy_kernel_to_fxregs
> arch/x86/include/asm/fpu/internal.h:164
>  [<     inline     >] __copy_kernel_to_fpregs
> arch/x86/include/asm/fpu/internal.h:454
>  [<ffffffff81096631>] kvm_load_guest_fpu.part.163+0xf1/0x340
> arch/x86/kvm/x86.c:7383
>  [<     inline     >] kvm_load_guest_fpu arch/x86/kvm/x86.c:6456
>  [<     inline     >] vcpu_enter_guest arch/x86/kvm/x86.c:6660
>  [<     inline     >] vcpu_run arch/x86/kvm/x86.c:6826
>  [<ffffffff810bb493>] kvm_arch_vcpu_ioctl_run+0x3b13/0x5a90
> arch/x86/kvm/x86.c:6984
>  [<ffffffff8106091e>] kvm_vcpu_ioctl+0x61e/0xdd0
> arch/x86/kvm/../../../virt/kvm/kvm_main.c:2557
>  [<     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
>  [<ffffffff831ebdc1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> reboot: cpu_has_vmx: ecx=80a02021 1

ping
this may be an information leak