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

Shannon Zhao
2014-09-26T05:58:03Z

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

--
Shannon