From: Andy Honig <ahonig@xxxxxxxxxx>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
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@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
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 3500dee9cf2b..57afcdaa2863 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -72,9 +72,12 @@ 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;
--
1.8.5.2
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