| Message ID | 20210128024451.1816770-1-michael.roth@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: fix CPUID entries returned by KVM_GET_CPUID2 ioctl | expand |
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
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>
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
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;
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(-)