Re: [PATCH] arm/arm64: KVM: Fix set_clear_sgi_pend_reg offset

Christoffer Dall
2014-09-26T10:16:08Z

On Fri, Sep 26, 2014 at 05:26:00PM +0800, Shannon Zhao wrote:
>
>
> On 2014/9/26 16:44, Christoffer Dall wrote:
> > Hi Shannon,
> >
> > On Fri, Sep 26, 2014 at 01:57:46PM +0800, Shannon Zhao wrote:
> >>
> >> On 2014/9/26 1:49, Christoffer Dall wrote:
> >>> The sgi values calculated in read_set_clear_sgi_pend_reg() and
> >>> write_set_clear_sgi_pend_reg() were horribly incorrectly multiplied by 4
> >>> with catastrophic results in that subfunctions ended up overwriting
> >>> memory not allocated for the expected purpose.
> >>>
> >>> This showed up as bugs in kfree() and the kernel complaining a lot of
> >>> you turn on memory debugging.
> >>>
> >>> This addresses: http://marc.info/?l=kvm&m=141164910007868&w=2
> >>>
> >>> Reported-by: Shannon Zhao <zhaoshenglong@huawei.com>
> >>> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> >>> ---
> >>> virt/kvm/arm/vgic.c | 4 ++--
> >>> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> >>> index b6fab0f..8629678 100644
> >>> --- a/virt/kvm/arm/vgic.c
> >>> +++ b/virt/kvm/arm/vgic.c
> >>> @@ -816,7 +816,7 @@ static bool read_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
> >>> {
> >>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> >>> int sgi;
> >>> - int min_sgi = (offset & ~0x3) * 4;
> >>> + int min_sgi = (offset & ~0x3);
> >>> int max_sgi = min_sgi + 3;
> >>> int vcpu_id = vcpu->vcpu_id;
> >>> u32 reg = 0;
> >>> @@ -837,7 +837,7 @@ static bool write_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
> >>> {
> >>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> >>> int sgi;
> >>> - int min_sgi = (offset & ~0x3) * 4;
> >>> + int min_sgi = (offset & ~0x3);
> >>> int max_sgi = min_sgi + 3;
> >>> int vcpu_id = vcpu->vcpu_id;
> >>> u32 reg;
> >>>
> >> Hi Christoffer,
> >>
> >> I have test this patch for a few hours. The kfree() bug doesn't appear again.
> >> But I come to another problem as followed.
> >> The test is that start 2 VMs, sleep 10 and do pkill qemu.
> >>
> >> qemu-system-aar[1207]: unhandled level 1 permission fault (11) at 0xffffc01ed6c200, esr 0x9200000d
> >> pgd = ffffffc012986000
> >> [ffffc01ed6c200] *pgd=0000000000000000, *pud=0000000000000000
> >>
> >> CPU: 1 PID: 1207 Comm: qemu-system-aar Not tainted 3.17.0-rc4+ #1
> >> task: ffffffc87b072900 ti: ffffffc0129e0000 task.ti: ffffffc0129e0000
> >> PC is at 0x4181a0
> >> LR is at 0x41826c
> >> pc : [<00000000004181a0>] lr : [<000000000041826c>] pstate: 80000000
> >> sp : 0000007fcd38ace0
> >> x29: 0000007fcd38ace0 x28: 0000000000000000
> >> x27: 0000000000000000 x26: 0000000000000000
> >> x25: 0000000000000000 x24: 0000000000000000
> >> x23: 0000000000000000 x22: 0000000000000000
> >> x21: 0000000000000000 x20: 0000000000000000
> >> x19: 0000007fcd38b070 x18: 0000007fcd38ab10
> >> x17: 0000007f9bb14480 x16: 00000000009f2370
> >> x15: ffffffffffffffff x14: 0000000000000000
> >> x13: 0000000000000000 x12: 0000000000000268
> >> x11: 00000000115e5520 x10: 0101010101010101
> >> x9 : 0000000000000004 x8 : 0000000000ac7a78
> >> x7 : 0000000000000000 x6 : 000000000000003f
> >> x5 : 0000000000000040 x4 : 0000000000000000
> >> x3 : 0000000000000030 x2 : 0000000000000001
> >> x1 : ffffffc01ed6c200 x0 : ffffffc01ed6c200
> >>
> > Hmmm, I just ran a similar loop with a number of tests in the VM for a
> > few hours and I didn't see this error.
> Yeah, it really need to run longer.
> After running about one hour this problem first appears and after running
> about 4 hours it second appears.
> >
> > In any case, this patch should still be merged, but we should try to
> > reproduce your setup.
> Your patch really solves the kfree() bug. I'll add tested-by line.
> >
> > What is your command line, exact QEMU version, the file system you use,
> > and the guest kernel you are running?
> My test script is as followed. QEMU version is v2.1.0 release.
> The fs is linaro-image-lamp-genericarmv8-20140727-701.rootfs.tar.gz.
> Host kernel is based on marc's branch "kvmtool-vgic-dyn" with your patch
> "Fix set_clear_sgi_pend_reg offset".
> Guest kernel is 3.16 release.
>
> while true
> do
> qemu-system-aarch64 \
> -enable-kvm -smp 4 \
> -kernel Image \
> -m 512 -machine virt,kernel_irqchip=on \
> -initrd guestfs.cpio.gz \
> -cpu host \
> -chardev pty,id=pty0,mux=on -monitor chardev:pty0 \
> -serial chardev:pty0 -daemonize \
> -vnc 0.0.0.0:0 \
> -append "rdinit=/sbin/init console=ttyAMA0 mem=512M root=/dev/ram earlyprintk=pl011,0x9000000 rw" &
>
> qemu-system-aarch64 \
> -enable-kvm -smp 4 \
> -kernel Image \
> -m 512 -machine virt,kernel_irqchip=on \
> -initrd guestfs.cpio.gz \
> -cpu host \
> -chardev pty,id=pty0,mux=on -monitor chardev:pty0 \
> -serial chardev:pty0 -daemonize \
> -vnc 0.0.0.0:1 \
> -append "rdinit=/sbin/init console=ttyAMA0 mem=512M root=/dev/ram earlyprintk=pl011,0x9000000 rw" &
> sleep 5
> pkill qemu

ok, I'll try to reproduce.

Thanks,
-Christoffer