[PATCH] hw/intc/loongarch_pch_pic: Validate htmsi_vector before indexing parent_irq

[Bin Guo <guobin@linux.alibaba.com>]

pch_pic_update_irq() used the guest-writable htmsi_vector[irq] value as an
index into parent_irq[] without checking bounds.  A value >= irq_num (64 in
the array, but only 32 are used by the virt machine) causes an out-of-bounds
read and a guest-triggerable QEMU crash.

Validate the vector before calling qemu_set_irq() in both the raise and lower
paths and log a guest error if it is out of range.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4114
Cc: qemu-stable@nongnu.org
Signed-off-by: Bin Guo <guobin@linux.alibaba.com>
---
 hw/intc/loongarch_pch_pic.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/hw/intc/loongarch_pch_pic.c b/hw/intc/loongarch_pch_pic.c
index 82e16be391..e87c7497c1 100644
--- a/hw/intc/loongarch_pch_pic.c
+++ b/hw/intc/loongarch_pch_pic.c
@@ -19,13 +19,21 @@ static void pch_pic_update_irq(LoongArchPICCommonState *s, uint64_t mask,
 {
     uint64_t val;
     int irq;
+    uint8_t vector;
 
     if (level) {
         val = mask & s->intirr & ~s->int_mask;
         if (val) {
             irq = ctz64(val);
+            vector = s->htmsi_vector[irq];
+            if (vector >= s->irq_num) {
+                qemu_log_mask(LOG_GUEST_ERROR,
+                              "%s: htmsi_vector[%d]=%u out of range\n",
+                              __func__, irq, vector);
+                return;
+            }
             s->intisr |= MAKE_64BIT_MASK(irq, 1);
-            qemu_set_irq(s->parent_irq[s->htmsi_vector[irq]], 1);
+            qemu_set_irq(s->parent_irq[vector], 1);
         }
     } else {
         /*
@@ -35,8 +43,15 @@ static void pch_pic_update_irq(LoongArchPICCommonState *s, uint64_t mask,
         val = mask & s->intisr & ~s->intirr;
         if (val) {
             irq = ctz64(val);
+            vector = s->htmsi_vector[irq];
+            if (vector >= s->irq_num) {
+                qemu_log_mask(LOG_GUEST_ERROR,
+                              "%s: htmsi_vector[%d]=%u out of range\n",
+                              __func__, irq, vector);
+                return;
+            }
             s->intisr &= ~MAKE_64BIT_MASK(irq, 1);
-            qemu_set_irq(s->parent_irq[s->htmsi_vector[irq]], 0);
+            qemu_set_irq(s->parent_irq[vector], 0);
         }
     }
 }
-- 
2.50.1 (Apple Git-155)