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

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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>
This commit is contained in:
Avi Kivity 2008-07-13 11:33:54 +03:00
parent 2a7c5b8b55
commit 722c05f219
1 changed files with 4 additions and 3 deletions
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7
arch/x86/kvm/mmu.c
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@ -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)
| PT_PRESENT_MASK | PT_WRITABLE_MASK
| shadow_user_mask | shadow_x_mask;
set_shadow_pte(&table[index],
__pa(new_table->spt)
| PT_PRESENT_MASK | PT_WRITABLE_MASK
| shadow_user_mask | shadow_x_mask);
}
table_addr = table[index] & PT64_BASE_ADDR_MASK;
}