hw/intc/arm_gicv3_its: Correct off-by-one bounds check on rdbase

The checks in the ITS on the rdbase values in guest commands are
off-by-one: they permit the guest to pass us a value equal to
s->gicv3->num_cpu, but the valid values are 0...num_cpu-1.  This
meant the guest could cause us to index off the end of the
s->gicv3->cpu[] array when calling gicv3_redist_process_lpi(), and we
would probably crash.

(This is not a security bug, because this code is only usable
with emulation, not with KVM.)

Cc: qemu-stable@nongnu.org
Fixes: 17fb5e36aabd4b ("hw/intc: GICv3 redistributor ITS processing")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/hw/intc/arm_gicv3_its.c b/hw/intc/arm_gicv3_its.c
index b99e63d..677b96d 100644
--- a/hw/intc/arm_gicv3_its.c
+++ b/hw/intc/arm_gicv3_its.c
@@ -311,7 +311,7 @@ static bool process_its_cmd(GICv3ITSState *s, uint64_t value, uint32_t offset,
          */
         rdbase = (cte & GITS_CTE_RDBASE_PROCNUM_MASK) >> 1U;
 
-        if (rdbase > s->gicv3->num_cpu) {
+        if (rdbase >= s->gicv3->num_cpu) {
             return result;
         }
 
@@ -505,7 +505,7 @@ static bool process_mapc(GICv3ITSState *s, uint32_t offset)
 
     valid = (value & CMD_FIELD_VALID_MASK);
 
-    if ((icid > s->ct.maxids.max_collids) || (rdbase > s->gicv3->num_cpu)) {
+    if ((icid > s->ct.maxids.max_collids) || (rdbase >= s->gicv3->num_cpu)) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "ITS MAPC: invalid collection table attributes "
                       "icid %d rdbase %" PRIu64 "\n",  icid, rdbase);