2020-09-14 13:48:41

by Vitaly Kuznetsov

Subject: [PATCH tip] KVM: nSVM: avoid freeing uninitialized pointers in svm_set_nested_state()

The save and ctl pointers are passed uninitialized to kfree() when
svm_set_nested_state() follows the 'goto out_set_gif' path. While
the issue could've been fixed by initializing these on-stack varialbles
to NULL, it seems preferable to eliminate 'out_set_gif' label completely
as it is not actually a failure path and duplicating a single svm_set_gif()
call doesn't look too bad.

Fixes: 6ccbd29ade0d ("KVM: SVM: nested: Don't allocate VMCB structures on stack")
Addresses-Coverity: ("Uninitialized pointer read")
Reported-by: Dan Carpenter <[email protected]>
Reported-by: Joerg Roedel <[email protected]>
Reported-by: Colin King <[email protected]>
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
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 598a769f1961..67e6d053985d 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1094,7 +1094,8 @@ 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))
@@ -1150,7 +1151,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
if (!nested_svm_vmrun_msrpm(svm))
return -EINVAL;

-out_set_gif:
svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));

ret = 0;
--
2.25.4

2020-09-14 15:12:26

by Sean Christopherson

Subject: Re: [PATCH tip] KVM: nSVM: avoid freeing uninitialized pointers in svm_set_nested_state()

On Mon, Sep 14, 2020 at 03:37:25PM +0200, Vitaly Kuznetsov wrote:
> The save and ctl pointers are passed uninitialized to kfree() when
> svm_set_nested_state() follows the 'goto out_set_gif' path. While
> the issue could've been fixed by initializing these on-stack varialbles
> to NULL, it seems preferable to eliminate 'out_set_gif' label completely
> as it is not actually a failure path and duplicating a single svm_set_gif()
> call doesn't look too bad.
>
> Fixes: 6ccbd29ade0d ("KVM: SVM: nested: Don't allocate VMCB structures on stack")
> Addresses-Coverity: ("Uninitialized pointer read")
> Reported-by: Dan Carpenter <[email protected]>
> Reported-by: Joerg Roedel <[email protected]>
> Reported-by: Colin King <[email protected]>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---

Reviewed-by: Sean Christopherson <[email protected]>

2020-09-14 15:48:03

by Jörg Rödel

Subject: Re: [PATCH tip] KVM: nSVM: avoid freeing uninitialized pointers in svm_set_nested_state()

On Mon, Sep 14, 2020 at 03:37:25PM +0200, Vitaly Kuznetsov wrote:
> The save and ctl pointers are passed uninitialized to kfree() when
> svm_set_nested_state() follows the 'goto out_set_gif' path. While
> the issue could've been fixed by initializing these on-stack varialbles
> to NULL, it seems preferable to eliminate 'out_set_gif' label completely
> as it is not actually a failure path and duplicating a single svm_set_gif()
> call doesn't look too bad.
>
> Fixes: 6ccbd29ade0d ("KVM: SVM: nested: Don't allocate VMCB structures on stack")
> Addresses-Coverity: ("Uninitialized pointer read")
> Reported-by: Dan Carpenter <[email protected]>
> Reported-by: Joerg Roedel <[email protected]>
> Reported-by: Colin King <[email protected]>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>

Acked-by: Joerg Roedel <[email protected]>

2020-09-14 16:09:32

by Tom Lendacky

Subject: Re: [PATCH tip] KVM: nSVM: avoid freeing uninitialized pointers in svm_set_nested_state()

On 9/14/20 8:37 AM, Vitaly Kuznetsov wrote:
> The save and ctl pointers are passed uninitialized to kfree() when
> svm_set_nested_state() follows the 'goto out_set_gif' path. While
> the issue could've been fixed by initializing these on-stack varialbles
> to NULL, it seems preferable to eliminate 'out_set_gif' label completely
> as it is not actually a failure path and duplicating a single svm_set_gif()
> call doesn't look too bad.
>
> Fixes: 6ccbd29ade0d ("KVM: SVM: nested: Don't allocate VMCB structures on stack")
> Addresses-Coverity: ("Uninitialized pointer read")
> Reported-by: Dan Carpenter <[email protected]>
> Reported-by: Joerg Roedel <[email protected]>
> Reported-by: Colin King <[email protected]>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>

Tested-by: Tom Lendacky <[email protected]>

2020-09-14 17:19:34

by tip-bot2 for Alexey Makhalov

Subject: [tip: x86/seves] KVM: nSVM: Avoid freeing uninitialized pointers in svm_set_nested_state()

The following commit has been merged into the x86/seves branch of tip:

Commit-ID: e6eb15c9ba3165698488ae5c34920eea20eaa38e
Gitweb: https://git.kernel.org/tip/e6eb15c9ba3165698488ae5c34920eea20eaa38e
Author: Vitaly Kuznetsov <[email protected]>
AuthorDate: Mon, 14 Sep 2020 15:37:25 +02:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Mon, 14 Sep 2020 18:08:54 +02:00

KVM: nSVM: Avoid freeing uninitialized pointers in svm_set_nested_state()

The save and ctl pointers are passed uninitialized to kfree() when
svm_set_nested_state() follows the 'goto out_set_gif' path. While the
issue could've been fixed by initializing these on-stack varialbles to
NULL, it seems preferable to eliminate 'out_set_gif' label completely as
it is not actually a failure path and duplicating a single svm_set_gif()
call doesn't look too bad.

[ bp: Drop obscure Addresses-Coverity: tag. ]

Fixes: 6ccbd29ade0d ("KVM: SVM: nested: Don't allocate VMCB structures on stack")
Reported-by: Dan Carpenter <[email protected]>
Reported-by: Joerg Roedel <[email protected]>
Reported-by: Colin King <[email protected]>
Signed-off-by: Vitaly Kuznetsov <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Acked-by: Joerg Roedel <[email protected]>
Tested-by: Tom Lendacky <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
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 2803662..d1ae94f 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;