Ignore attempts to complete non-existent IRQs; this fixes a buffer
overrun if the guest writes a bad value to the GICC_EOIR register.
(This case is UNPREDICTABLE so ignoring it is a valid choice.)
Note that doing nothing if the guest writes 1023 to this register
is not in fact a change in behaviour: the old code would also
always do nothing in this case but in a non-obvious way.
(The buffer overrun was noted by Coverity, see bug 887883.)
Signed-off-by: Peter Maydell
---
It looks to me as if Coverity is being alarmist about the other alleged
static overruns in this file...
hw/arm_gic.c | 27 ++-
1 files changed, 18 insertions(+), 9 deletions(-)
diff --git a/hw/arm_gic.c b/hw/arm_gic.c
index f3f3516..527c9ce 100644
--- a/hw/arm_gic.c
+++ b/hw/arm_gic.c
@@ -215,17 +215,26 @@ static void gic_complete_irq(gic_state * s, int cpu, int
irq)
int update = 0;
int cm = 1 << cpu;
DPRINTF("EOI %d\n", irq);
+if (irq >= GIC_NIRQ) {
+/* This handles two cases:
+ * 1. If software writes the ID of a spurious interrupt [ie 1023]
+ * to the GICC_EOIR, the GIC ignores that write.
+ * 2. If software writes the number of a non-existent interrupt
+ * this must be a subcase of "value written does not match the last
+ * valid interrupt value read from the Interrupt Acknowledge
+ * register" and so this is UNPREDICTABLE. We choose to ignore it.
+ */
+return;
+}
if (s->running_irq[cpu] == 1023)
return; /* No active IRQ. */
-if (irq != 1023) {
-/* Mark level triggered interrupts as pending if they are still
- raised. */
-if (!GIC_TEST_TRIGGER(irq) && GIC_TEST_ENABLED(irq, cm)
-&& GIC_TEST_LEVEL(irq, cm) && (GIC_TARGET(irq) & cm) != 0) {
-DPRINTF("Set %d pending mask %x\n", irq, cm);
-GIC_SET_PENDING(irq, cm);
-update = 1;
-}
+/* Mark level triggered interrupts as pending if they are still
+ raised. */
+if (!GIC_TEST_TRIGGER(irq) && GIC_TEST_ENABLED(irq, cm)
+&& GIC_TEST_LEVEL(irq, cm) && (GIC_TARGET(irq) & cm) != 0) {
+DPRINTF("Set %d pending mask %x\n", irq, cm);
+GIC_SET_PENDING(irq, cm);
+update = 1;
}
if (irq != s->running_irq[cpu]) {
/* Complete an IRQ that is not currently running. */
--
1.7.1
