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Subject[ 057/184] KVM: Fix bounds checking in ioapic indirect register
2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
reads (CVE-2013-1798)

From: Andy Honig <ahonig@google.com>

commit a2c118bfab8bc6b8bb213abfc35201e441693d55 upstream.

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>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
virt/kvm/ioapic.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 9fe140b..69969ae 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -71,9 +71,12 @@ 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;
--
1.7.12.2.21.g234cd45.dirty




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