* [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl
@ 2021-01-28 2:44 Michael Roth
2021-01-28 7:40 ` Paolo Bonzini
2021-01-28 8:36 ` Vitaly Kuznetsov
0 siblings, 2 replies; 4+ messages in thread
From: Michael Roth @ 2021-01-28 2:44 UTC (permalink / raw)
To: kvm
Cc: Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li,
Jim Mattson, Joerg Roedel, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, x86, H . Peter Anvin, linux-kernel,
Michael Roth
Recent commit 255cbecfe0 modified struct kvm_vcpu_arch to make
'cpuid_entries' a pointer to an array of kvm_cpuid_entry2 entries
rather than embedding the array in the struct. KVM_SET_CPUID and
KVM_SET_CPUID2 were updated accordingly, but KVM_GET_CPUID2 was missed.
As a result, KVM_GET_CPUID2 currently returns random fields from struct
kvm_vcpu_arch to userspace rather than the expected CPUID values. Fix
this by treating 'cpuid_entries' as a pointer when copying its
contents to userspace buffer.
Fixes: 255cbecfe0c9 ("KVM: x86: allocate vcpu->arch.cpuid_entries dynamically")
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Michael Roth <michael.roth@amd.com.com>
---
arch/x86/kvm/cpuid.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 13036cf0b912..38172ca627d3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -321,7 +321,7 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
if (cpuid->nent < vcpu->arch.cpuid_nent)
goto out;
r = -EFAULT;
- if (copy_to_user(entries, &vcpu->arch.cpuid_entries,
+ if (copy_to_user(entries, vcpu->arch.cpuid_entries,
vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2)))
goto out;
return 0;
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl
2021-01-28 2:44 [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl Michael Roth
@ 2021-01-28 7:40 ` Paolo Bonzini
2021-01-28 8:36 ` Vitaly Kuznetsov
1 sibling, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2021-01-28 7:40 UTC (permalink / raw)
To: Michael Roth, kvm
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
H . Peter Anvin, linux-kernel, Michael Roth
On 28/01/21 03:44, Michael Roth wrote:
> Recent commit 255cbecfe0 modified struct kvm_vcpu_arch to make
> 'cpuid_entries' a pointer to an array of kvm_cpuid_entry2 entries
> rather than embedding the array in the struct. KVM_SET_CPUID and
> KVM_SET_CPUID2 were updated accordingly, but KVM_GET_CPUID2 was missed.
>
> As a result, KVM_GET_CPUID2 currently returns random fields from struct
> kvm_vcpu_arch to userspace rather than the expected CPUID values. Fix
> this by treating 'cpuid_entries' as a pointer when copying its
> contents to userspace buffer.
>
> Fixes: 255cbecfe0c9 ("KVM: x86: allocate vcpu->arch.cpuid_entries dynamically")
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com.com>
> ---
> arch/x86/kvm/cpuid.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 13036cf0b912..38172ca627d3 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -321,7 +321,7 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
> if (cpuid->nent < vcpu->arch.cpuid_nent)
> goto out;
> r = -EFAULT;
> - if (copy_to_user(entries, &vcpu->arch.cpuid_entries,
> + if (copy_to_user(entries, vcpu->arch.cpuid_entries,
> vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2)))
> goto out;
> return 0;
>
Queued, thanks. I'll also write a testcase.
Paolo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl
2021-01-28 2:44 [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl Michael Roth
2021-01-28 7:40 ` Paolo Bonzini
@ 2021-01-28 8:36 ` Vitaly Kuznetsov
2021-01-28 8:43 ` Paolo Bonzini
1 sibling, 1 reply; 4+ messages in thread
From: Vitaly Kuznetsov @ 2021-01-28 8:36 UTC (permalink / raw)
To: Michael Roth, kvm
Cc: Paolo Bonzini, Sean Christopherson, Wanpeng Li, Jim Mattson,
Joerg Roedel, Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
H . Peter Anvin, linux-kernel, Michael Roth
Michael Roth <michael.roth@amd.com> writes:
> Recent commit 255cbecfe0 modified struct kvm_vcpu_arch to make
> 'cpuid_entries' a pointer to an array of kvm_cpuid_entry2 entries
> rather than embedding the array in the struct. KVM_SET_CPUID and
> KVM_SET_CPUID2 were updated accordingly, but KVM_GET_CPUID2 was missed.
>
> As a result, KVM_GET_CPUID2 currently returns random fields from struct
> kvm_vcpu_arch to userspace rather than the expected CPUID values. Fix
> this by treating 'cpuid_entries' as a pointer when copying its
> contents to userspace buffer.
>
> Fixes: 255cbecfe0c9 ("KVM: x86: allocate vcpu->arch.cpuid_entries dynamically")
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com.com>
> ---
> arch/x86/kvm/cpuid.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 13036cf0b912..38172ca627d3 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -321,7 +321,7 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
> if (cpuid->nent < vcpu->arch.cpuid_nent)
> goto out;
> r = -EFAULT;
> - if (copy_to_user(entries, &vcpu->arch.cpuid_entries,
> + if (copy_to_user(entries, vcpu->arch.cpuid_entries,
> vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2)))
> goto out;
> return 0;
This is embarrassing but I have a (possible) excuse: copy_to_user's
argument is 'void *' so no warning was produced. Surprisingly, no test
caught the breakage. Thanks for debugging and fixing!
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl
2021-01-28 8:36 ` Vitaly Kuznetsov
@ 2021-01-28 8:43 ` Paolo Bonzini
0 siblings, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2021-01-28 8:43 UTC (permalink / raw)
To: Vitaly Kuznetsov, Michael Roth, kvm
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Joerg Roedel,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
H . Peter Anvin, linux-kernel, Michael Roth
On 28/01/21 09:36, Vitaly Kuznetsov wrote:
> This is embarrassing but I have a (possible) excuse: copy_to_user's
> argument is 'void *' so no warning was produced. Surprisingly, no test
> caught the breakage. Thanks for debugging and fixing!
So who writes the test:
- the author of the buggy patch
- the maintainer who failed to spot it
- the poor sod who fixed the issue
?
(Just kidding, it will of course be either me or a fourth person :)).
Paolo
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-01-28 8:57 UTC | newest]
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2021-01-28 2:44 [PATCH] KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl Michael Roth
2021-01-28 7:40 ` Paolo Bonzini
2021-01-28 8:36 ` Vitaly Kuznetsov
2021-01-28 8:43 ` Paolo Bonzini
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