[069/126] KVM: Fix bounds checking in ioapic indirect register reads (CVE-2013-1798)

Steven Rostedt
2013-05-07T04:31:12Z

[-- Attachment #1: 0069-KVM-Fix-bounds-checking-in-ioapic-indirect-register-.patch --]
[-- Type: text/plain, Size: 1622 bytes --]

3.6.11.3 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Andy Honig <ahonig@google.com>

[ Upstream commit a2c118bfab8bc6b8bb213abfc35201e441693d55 ]

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: Steven Rostedt <rostedt@goodmis.org>
---
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 ef61d52..92b1e28 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -73,9 +73,12 @@ 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;
--
1.7.10.4