* [PATCH] KVM: x86: Fix uninitialized return value bug in EXIT_HYPERCALL enabling
@ 2021-06-24 18:06 Sean Christopherson
2021-06-24 18:19 ` Paolo Bonzini
0 siblings, 1 reply; 4+ messages in thread
From: Sean Christopherson @ 2021-06-24 18:06 UTC (permalink / raw)
To: Paolo Bonzini, Nathan Chancellor, Nick Desaulniers
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, clang-built-linux, linux-kernel
Zero out 'r' on success in the KVM_CAP_EXIT_HYPERCALL case. As noted by
clang, the happy path will return an uninitialized value:
arch/x86/kvm/x86.c:5649:7: error: variable 'r' is used uninitialized
whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kvm/x86.c:5663:9: note: uninitialized use occurs here
return r;
^
arch/x86/kvm/x86.c:5649:3: note: remove the 'if' if its condition is always true
if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kvm/x86.c:5540:7: note: initialize the variable 'r' to silence this warning
int r;
^
= 0
Opportunistically move the "r = -EINVAL;" above the check to match the
pattern used in almost all other cases.
Fixes: 0dbb11230437 ("KVM: X86: Introduce KVM_HC_MAP_GPA_RANGE hypercall")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e4cea00c49a3..647922ba97df 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5646,11 +5646,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
r = kvm_x86_ops.vm_copy_enc_context_from(kvm, cap->args[0]);
return r;
case KVM_CAP_EXIT_HYPERCALL:
- if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
- r = -EINVAL;
+ r = -EINVAL;
+ if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK)
break;
- }
+
kvm->arch.hypercall_exit_enabled = cap->args[0];
+ r = 0;
break;
case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
kvm->arch.exit_on_emulation_error = cap->args[0];
--
2.32.0.93.g670b81a890-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: Fix uninitialized return value bug in EXIT_HYPERCALL enabling
2021-06-24 18:06 [PATCH] KVM: x86: Fix uninitialized return value bug in EXIT_HYPERCALL enabling Sean Christopherson
@ 2021-06-24 18:19 ` Paolo Bonzini
2021-06-24 18:20 ` Nick Desaulniers
0 siblings, 1 reply; 4+ messages in thread
From: Paolo Bonzini @ 2021-06-24 18:19 UTC (permalink / raw)
To: Sean Christopherson, Nathan Chancellor, Nick Desaulniers
Cc: Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
clang-built-linux, linux-kernel
On 24/06/21 20:06, Sean Christopherson wrote:
> Zero out 'r' on success in the KVM_CAP_EXIT_HYPERCALL case. As noted by
> clang, the happy path will return an uninitialized value:
>
> arch/x86/kvm/x86.c:5649:7: error: variable 'r' is used uninitialized
> whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/x86/kvm/x86.c:5663:9: note: uninitialized use occurs here
> return r;
> ^
> arch/x86/kvm/x86.c:5649:3: note: remove the 'if' if its condition is always true
> if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/x86/kvm/x86.c:5540:7: note: initialize the variable 'r' to silence this warning
> int r;
> ^
> = 0
>
> Opportunistically move the "r = -EINVAL;" above the check to match the
> pattern used in almost all other cases.
>
> Fixes: 0dbb11230437 ("KVM: X86: Introduce KVM_HC_MAP_GPA_RANGE hypercall")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Actually it was not that patch, but rather a botched conflict resolution
when applying (too late at night) Aaron's emulation failure patch:
@@ -5647,6 +5648,9 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
break;
}
kvm->arch.hypercall_exit_enabled = cap->args[0];
+ break;
+ case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
+ kvm->arch.exit_on_emulation_error = cap->args[0];
r = 0;
break;
default:
I have already fixed this locally, though I haven't pushed it to kvm.git
yet; my tests should finish running in about an hour, and then I'll push
everything to kvm/next, except for the C bit fixes.
Paolo
> ---
> arch/x86/kvm/x86.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e4cea00c49a3..647922ba97df 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5646,11 +5646,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
> r = kvm_x86_ops.vm_copy_enc_context_from(kvm, cap->args[0]);
> return r;
> case KVM_CAP_EXIT_HYPERCALL:
> - if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
> - r = -EINVAL;
> + r = -EINVAL;
> + if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK)
> break;
> - }
> +
> kvm->arch.hypercall_exit_enabled = cap->args[0];
> + r = 0;
> break;
> case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
> kvm->arch.exit_on_emulation_error = cap->args[0];
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: Fix uninitialized return value bug in EXIT_HYPERCALL enabling
2021-06-24 18:19 ` Paolo Bonzini
@ 2021-06-24 18:20 ` Nick Desaulniers
2021-06-24 18:22 ` Sean Christopherson
0 siblings, 1 reply; 4+ messages in thread
From: Nick Desaulniers @ 2021-06-24 18:20 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Sean Christopherson, Nathan Chancellor, Vitaly Kuznetsov,
Wanpeng Li, Jim Mattson, Joerg Roedel, kvm, clang-built-linux,
linux-kernel
On Thu, Jun 24, 2021 at 11:19 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> I have already fixed this locally, though I haven't pushed it to kvm.git
> yet; my tests should finish running in about an hour, and then I'll push
> everything to kvm/next, except for the C bit fixes.
Ah, I was looking at this case in linux-next, and
0dbb11230437895f7cd6fc55da61cef011e997d8 wondering what was going on!
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: Fix uninitialized return value bug in EXIT_HYPERCALL enabling
2021-06-24 18:20 ` Nick Desaulniers
@ 2021-06-24 18:22 ` Sean Christopherson
0 siblings, 0 replies; 4+ messages in thread
From: Sean Christopherson @ 2021-06-24 18:22 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Paolo Bonzini, Nathan Chancellor, Vitaly Kuznetsov, Wanpeng Li,
Jim Mattson, Joerg Roedel, kvm, clang-built-linux, linux-kernel
On Thu, Jun 24, 2021, Nick Desaulniers wrote:
> On Thu, Jun 24, 2021 at 11:19 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> > I have already fixed this locally, though I haven't pushed it to kvm.git
> > yet; my tests should finish running in about an hour, and then I'll push
> > everything to kvm/next, except for the C bit fixes.
>
> Ah, I was looking at this case in linux-next, and
> 0dbb11230437895f7cd6fc55da61cef011e997d8 wondering what was going on!
Doh, I obviously didn't look too closely at the blame.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-06-24 18:06 [PATCH] KVM: x86: Fix uninitialized return value bug in EXIT_HYPERCALL enabling Sean Christopherson
2021-06-24 18:19 ` Paolo Bonzini
2021-06-24 18:20 ` Nick Desaulniers
2021-06-24 18:22 ` Sean Christopherson
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