Commit 5b73d634 authored by David Gibson's avatar David Gibson Committed by Paul Mackerras

KVM: PPC: Book3S HV: Prevent double-free on HPT resize commit path

resize_hpt_release(), called once the HPT resize of a KVM guest is
completed (successfully or unsuccessfully) frees 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: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent ee106891
...@@ -1407,6 +1407,9 @@ static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize) ...@@ -1407,6 +1407,9 @@ static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize)
{ {
BUG_ON(kvm->arch.resize_hpt != resize); BUG_ON(kvm->arch.resize_hpt != resize);
if (!resize)
return;
if (resize->hpt.virt) if (resize->hpt.virt)
kvmppc_free_hpt(&resize->hpt); kvmppc_free_hpt(&resize->hpt);
......
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