From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Colin King <colin.king@canonical.com>
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"maintainer\:X86 ARCHITECTURE" <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH][next] KVM: SVM: nested: fix free of uninitialized pointers save and ctl
Date: Fri, 11 Sep 2020 13:49:42 +0200 [thread overview]
Message-ID: <87o8mclei1.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200911110730.24238-1-colin.king@canonical.com>
Colin King <colin.king@canonical.com> writes:
> From: Colin Ian King <colin.king@canonical.com>
>
> Currently the error exit path to outt_set_gif will kfree on
> uninitialized
typo: out_set_gif
> pointers save and ctl. Fix this by ensuring these pointers are
> inintialized to NULL to avoid garbage pointer freeing.
>
> Addresses-Coverity: ("Uninitialized pointer read")
> Fixes: 6ccbd29ade0d ("KVM: SVM: nested: Don't allocate VMCB structures
> on stack")
Where is this commit id from? I don't see it in Paolo's kvm tree, if
it's not yet merged, maybe we should fix it and avoid introducing the
issue in the first place?
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> arch/x86/kvm/svm/nested.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 28036629abf8..2b15f49f9e5a 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1060,8 +1060,8 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> struct vmcb *hsave = svm->nested.hsave;
> struct vmcb __user *user_vmcb = (struct vmcb __user *)
> &user_kvm_nested_state->data.svm[0];
> - struct vmcb_control_area *ctl;
> - struct vmcb_save_area *save;
> + struct vmcb_control_area *ctl = NULL;
> + struct vmcb_save_area *save = NULL;
> int ret;
> u32 cr0;
I think it would be better if we eliminate 'out_set_gif; completely as
the 'error path' we have looks a bit weird anyway. Something like
(untested):
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 28036629abf8..d1ae94f40907 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1092,7 +1092,8 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
if (!(kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE)) {
svm_leave_nested(svm);
- goto out_set_gif;
+ svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
+ return 0;
}
if (!page_address_valid(vcpu, kvm_state->hdr.svm.vmcb_pa))
@@ -1145,7 +1146,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
load_nested_vmcb_control(svm, ctl);
nested_prepare_vmcb_control(svm);
-out_set_gif:
svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
ret = 0;
--
Vitaly
next prev parent reply other threads:[~2020-09-11 11:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 11:07 [PATCH][next] KVM: SVM: nested: fix free of uninitialized pointers save and ctl Colin King
2020-09-11 11:49 ` Vitaly Kuznetsov [this message]
2020-09-11 16:28 ` Sean Christopherson
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