Re: [PATCH] KVM: Prevent double-free on HPT resize commit path
From: David Gibson <hidden>
Date: 2017-02-28 01:20:27
Also in:
kvm, linuxppc-dev
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 <redacted> Signed-off-by: David Gibson <redacted>
Ping, Paul have you taken this one?
quoted hunk ↗ jump to hunk
--- 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
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