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Commit a2c118bf authored by Andy Honig's avatar Andy Honig Committed by Marcelo Tosatti
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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: default avatarAndrew Honig <ahonig@google.com>
Signed-off-by: default avatarMarcelo 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;