softmmu: Assert data in bounds in iotlb_to_section

Acked-by: Alex Bennée <alex.bennee@linaro.org>
Suggested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
(cherry picked from commit 86e4f93)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

softmmu/physmem.c

@@ -2413,9 +2413,15 @@ MemoryRegionSection *iotlb_to_section(CPUState *cpu,
     int asidx = cpu_asidx_from_attrs(cpu, attrs);
     CPUAddressSpace *cpuas = &cpu->cpu_ases[asidx];
     AddressSpaceDispatch *d = qatomic_rcu_read(&cpuas->memory_dispatch);
-    MemoryRegionSection *sections = d->map.sections;
+    int section_index = index & ~TARGET_PAGE_MASK;
+    MemoryRegionSection *ret;
+
+    assert(section_index < d->map.sections_nb);
+    ret = d->map.sections + section_index;
+    assert(ret->mr);
+    assert(ret->mr->ops);
 
-    return &sections[index & ~TARGET_PAGE_MASK];
+    return ret;
 }
 
 static void io_mem_init(void)