Commit 722c05f2 authored Jul 13, 2008 by Avi Kivity

KVM: MMU: Fix potential race setting upper shadow ptes on nonpae hosts



The direct mapped shadow code (used for real mode and two dimensional paging)
sets upper-level ptes using direct assignment rather than calling
set_shadow_pte().  A nonpae host will split this into two writes, which opens
up a race if another vcpu accesses the same memory area.

Fix by calling set_shadow_pte() instead of assigning directly.

Noticed by Izik Eidus.

Signed-off-by: Avi Kivity <avi@qumranet.com>

parent 2a7c5b8b

arch/x86/kvm/mmu.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1189,9 +1189,10 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
		return -ENOMEM;
		}

		table[index] = __pa(new_table->spt)
		set_shadow_pte(&table[index],
		__pa(new_table->spt)
		\| PT_PRESENT_MASK \| PT_WRITABLE_MASK
		\| shadow_user_mask \| shadow_x_mask;
		\| shadow_user_mask \| shadow_x_mask);
		}
		table_addr = table[index] & PT64_BASE_ADDR_MASK;
		}