* [PATCH] KVM: Prevent double-free on HPT resize commit path
@ 2017-02-15 3:40 David Gibson
2017-02-28 0:56 ` David Gibson
0 siblings, 1 reply; 3+ messages in thread
From: David Gibson @ 2017-02-15 3:40 UTC (permalink / raw)
To: paulus
Cc: dan.carpenter, linuxppc-dev, kvm-ppc, kvm, linux-kernel, David Gibson
resize_hpt_release(), called once the HPT resize of a KVM guest is
completed (successfully or unsuccessfully) free()s the state structure for
the resize. It is currently not safe to call with a NULL pointer.
However, one of the error paths in kvm_vm_ioctl_resize_hpt_commit() can
invoke it with a NULL pointer. This will occur if userspace improperly
invokes KVM_PPC_RESIZE_HPT_COMMIT without previously calling
KVM_PPC_RESIZE_HPT_PREPARE, or if it calls COMMIT twice without an
intervening PREPARE.
To fix this potential crash bug - and maybe others like it, make it safe
(and a no-op) to call resize_hpt_release() with a NULL resize pointer.
Found by Dan Carpenter with a static checker.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
arch/powerpc/kvm/book3s_64_mmu_hv.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 013552f..72ccac2 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -1407,6 +1407,9 @@ static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize)
{
BUG_ON(kvm->arch.resize_hpt != resize);
+ if (!resize)
+ return;
+
if (resize->hpt.virt)
kvmppc_free_hpt(&resize->hpt);
--
2.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: Prevent double-free on HPT resize commit path
2017-02-15 3:40 [PATCH] KVM: Prevent double-free on HPT resize commit path David Gibson
@ 2017-02-28 0:56 ` David Gibson
2017-02-28 4:59 ` Paul Mackerras
0 siblings, 1 reply; 3+ messages in thread
From: David Gibson @ 2017-02-28 0:56 UTC (permalink / raw)
To: paulus; +Cc: dan.carpenter, linuxppc-dev, kvm-ppc, kvm, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 1736 bytes --]
On Wed, Feb 15, 2017 at 02:40:04PM +1100, David Gibson wrote:
> resize_hpt_release(), called once the HPT resize of a KVM guest is
> completed (successfully or unsuccessfully) free()s the state structure for
> the resize. It is currently not safe to call with a NULL pointer.
>
> However, one of the error paths in kvm_vm_ioctl_resize_hpt_commit() can
> invoke it with a NULL pointer. This will occur if userspace improperly
> invokes KVM_PPC_RESIZE_HPT_COMMIT without previously calling
> KVM_PPC_RESIZE_HPT_PREPARE, or if it calls COMMIT twice without an
> intervening PREPARE.
>
> To fix this potential crash bug - and maybe others like it, make it safe
> (and a no-op) to call resize_hpt_release() with a NULL resize pointer.
>
> Found by Dan Carpenter with a static checker.
>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Ping,
Paul have you taken this one?
> ---
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 013552f..72ccac2 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -1407,6 +1407,9 @@ static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize)
> {
> BUG_ON(kvm->arch.resize_hpt != resize);
>
> + if (!resize)
> + return;
> +
> if (resize->hpt.virt)
> kvmppc_free_hpt(&resize->hpt);
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: Prevent double-free on HPT resize commit path
2017-02-28 0:56 ` David Gibson
@ 2017-02-28 4:59 ` Paul Mackerras
0 siblings, 0 replies; 3+ messages in thread
From: Paul Mackerras @ 2017-02-28 4:59 UTC (permalink / raw)
To: David Gibson; +Cc: dan.carpenter, linuxppc-dev, kvm-ppc, kvm, linux-kernel
On Tue, Feb 28, 2017 at 11:56:55AM +1100, David Gibson wrote:
> On Wed, Feb 15, 2017 at 02:40:04PM +1100, David Gibson wrote:
> > resize_hpt_release(), called once the HPT resize of a KVM guest is
> > completed (successfully or unsuccessfully) free()s the state structure for
> > the resize. It is currently not safe to call with a NULL pointer.
> >
> > However, one of the error paths in kvm_vm_ioctl_resize_hpt_commit() can
> > invoke it with a NULL pointer. This will occur if userspace improperly
> > invokes KVM_PPC_RESIZE_HPT_COMMIT without previously calling
> > KVM_PPC_RESIZE_HPT_PREPARE, or if it calls COMMIT twice without an
> > intervening PREPARE.
> >
> > To fix this potential crash bug - and maybe others like it, make it safe
> > (and a no-op) to call resize_hpt_release() with a NULL resize pointer.
> >
> > Found by Dan Carpenter with a static checker.
> >
> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
>
> Ping,
>
> Paul have you taken this one?
Yes, thanks, it's in Linus' tree now.
Paul.
^ permalink raw reply [flat|nested] 3+ messages in thread
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