Commit a2c118bf authored Feb 20, 2013 by Andy Honig Committed by Marcelo Tosatti Mar 19, 2013

KVM: Fix bounds checking in ioapic indirect register reads (CVE-2013-1798)



If the guest specifies a IOAPIC_REG_SELECT with an invalid value and follows
that with a read of the IOAPIC_REG_WINDOW KVM does not properly validate
that request.  ioapic_read_indirect contains an
ASSERT(redir_index < IOAPIC_NUM_PINS), but the ASSERT has no effect in
non-debug builds.  In recent kernels this allows a guest to cause a kernel
oops by reading invalid memory.  In older kernels (pre-3.3) this allows a
guest to read from large ranges of host memory.

Tested: tested against apic unit tests.

Signed-off-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

parent 0b79459b

virt/kvm/ioapic.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -74,9 +74,12 @@ static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
		u32 redir_index = (ioapic->ioregsel - 0x10) >> 1;
		u64 redir_content;

		ASSERT(redir_index < IOAPIC_NUM_PINS);
		if (redir_index < IOAPIC_NUM_PINS)
		redir_content =
		ioapic->redirtbl[redir_index].bits;
		else
		redir_content = ~0ULL;

		redir_content = ioapic->redirtbl[redir_index].bits;
		result = (ioapic->ioregsel & 0x1) ?
		(redir_content >> 32) & 0xffffffff :
		redir_content & 0xffffffff;

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