| From | Ben Hutchings <> | Date | Mon, 22 Apr 2013 15:25:59 +0100 | Subject | [73/75] KVM: Fix bounds checking in ioapic indirect register reads (CVE-2013-1798) |
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3.2.44-rc1 review patch. If anyone has any objections, please let me know.
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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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- virt/kvm/ioapic.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/virt/kvm/ioapic.c +++ b/virt/kvm/ioapic.c @@ -73,9 +73,12 @@ static unsigned long ioapic_read_indirec 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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