* [PATCH] KVM: x86: Account for 32-bit kernels when handling address in TSC attrs
@ 2021-10-07 23:16 Sean Christopherson
2021-10-11 14:35 ` Oliver Upton
0 siblings, 1 reply; 3+ messages in thread
From: Sean Christopherson @ 2021-10-07 23:16 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel, Oliver Upton
When handling TSC attributes, cast the userspace provided virtual address
to an unsigned long before casting it to a pointer to fix warnings on
32-bit kernels due to casting a 64-bit integer to a 32-bit pointer.
Add a check that the truncated address matches the original address, e.g.
to prevent userspace specifying garbage in bits 63:32.
arch/x86/kvm/x86.c: In function ‘kvm_arch_tsc_get_attr’:
arch/x86/kvm/x86.c:4947:22: error: cast to pointer from integer of different size
4947 | u64 __user *uaddr = (u64 __user *)attr->addr;
| ^
arch/x86/kvm/x86.c: In function ‘kvm_arch_tsc_set_attr’:
arch/x86/kvm/x86.c:4967:22: error: cast to pointer from integer of different size
4967 | u64 __user *uaddr = (u64 __user *)attr->addr;
| ^
Cc: Oliver Upton <oupton@google.com>
Fixes: 469fde25e680 ("KVM: x86: Expose TSC offset controls to userspace")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 196ac33ef958..4a52a08707de 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4944,9 +4944,12 @@ static int kvm_arch_tsc_has_attr(struct kvm_vcpu *vcpu,
static int kvm_arch_tsc_get_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr)
{
- u64 __user *uaddr = (u64 __user *)attr->addr;
+ u64 __user *uaddr = (u64 __user *)(unsigned long)attr->addr;
int r;
+ if ((u64)(unsigned long)uaddr != attr->addr)
+ return -EFAULT;
+
switch (attr->attr) {
case KVM_VCPU_TSC_OFFSET:
r = -EFAULT;
@@ -4964,10 +4967,13 @@ static int kvm_arch_tsc_get_attr(struct kvm_vcpu *vcpu,
static int kvm_arch_tsc_set_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr)
{
- u64 __user *uaddr = (u64 __user *)attr->addr;
+ u64 __user *uaddr = (u64 __user *)(unsigned long)attr->addr;
struct kvm *kvm = vcpu->kvm;
int r;
+ if ((u64)(unsigned long)uaddr != attr->addr)
+ return -EFAULT;
+
switch (attr->attr) {
case KVM_VCPU_TSC_OFFSET: {
u64 offset, tsc, ns;
--
2.33.0.882.g93a45727a2-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: Account for 32-bit kernels when handling address in TSC attrs
2021-10-07 23:16 [PATCH] KVM: x86: Account for 32-bit kernels when handling address in TSC attrs Sean Christopherson
@ 2021-10-11 14:35 ` Oliver Upton
2021-10-15 16:06 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Oliver Upton @ 2021-10-11 14:35 UTC (permalink / raw)
To: Sean Christopherson
Cc: Paolo Bonzini, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel
On Thu, Oct 7, 2021 at 6:16 PM Sean Christopherson <seanjc@google.com> wrote:
>
> When handling TSC attributes, cast the userspace provided virtual address
> to an unsigned long before casting it to a pointer to fix warnings on
> 32-bit kernels due to casting a 64-bit integer to a 32-bit pointer.
>
> Add a check that the truncated address matches the original address, e.g.
> to prevent userspace specifying garbage in bits 63:32.
>
> arch/x86/kvm/x86.c: In function ‘kvm_arch_tsc_get_attr’:
> arch/x86/kvm/x86.c:4947:22: error: cast to pointer from integer of different size
> 4947 | u64 __user *uaddr = (u64 __user *)attr->addr;
> | ^
> arch/x86/kvm/x86.c: In function ‘kvm_arch_tsc_set_attr’:
> arch/x86/kvm/x86.c:4967:22: error: cast to pointer from integer of different size
> 4967 | u64 __user *uaddr = (u64 __user *)attr->addr;
> | ^
>
> Cc: Oliver Upton <oupton@google.com>
> Fixes: 469fde25e680 ("KVM: x86: Expose TSC offset controls to userspace")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/x86.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
Reviewed-by: Oliver Upton <oupton@google.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: Account for 32-bit kernels when handling address in TSC attrs
2021-10-11 14:35 ` Oliver Upton
@ 2021-10-15 16:06 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2021-10-15 16:06 UTC (permalink / raw)
To: Oliver Upton, Sean Christopherson
Cc: Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
linux-kernel
On 11/10/21 16:35, Oliver Upton wrote:
> On Thu, Oct 7, 2021 at 6:16 PM Sean Christopherson <seanjc@google.com> wrote:
>>
>> When handling TSC attributes, cast the userspace provided virtual address
>> to an unsigned long before casting it to a pointer to fix warnings on
>> 32-bit kernels due to casting a 64-bit integer to a 32-bit pointer.
>>
>> Add a check that the truncated address matches the original address, e.g.
>> to prevent userspace specifying garbage in bits 63:32.
>>
>> arch/x86/kvm/x86.c: In function ‘kvm_arch_tsc_get_attr’:
>> arch/x86/kvm/x86.c:4947:22: error: cast to pointer from integer of different size
>> 4947 | u64 __user *uaddr = (u64 __user *)attr->addr;
>> | ^
>> arch/x86/kvm/x86.c: In function ‘kvm_arch_tsc_set_attr’:
>> arch/x86/kvm/x86.c:4967:22: error: cast to pointer from integer of different size
>> 4967 | u64 __user *uaddr = (u64 __user *)attr->addr;
>> | ^
>>
>> Cc: Oliver Upton <oupton@google.com>
>> Fixes: 469fde25e680 ("KVM: x86: Expose TSC offset controls to userspace")
>> Signed-off-by: Sean Christopherson <seanjc@google.com>
>> ---
>> arch/x86/kvm/x86.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>
>
> Reviewed-by: Oliver Upton <oupton@google.com>
>
Squashed, thanks.
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-10-07 23:16 [PATCH] KVM: x86: Account for 32-bit kernels when handling address in TSC attrs Sean Christopherson
2021-10-11 14:35 ` Oliver Upton
2021-10-15 16:06 ` Paolo Bonzini
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