[PATCH-for-5.2 v3] util/cutils: Fix Coverity array overrun in freq_to_str()

[Philippe Mathieu-Daudé]

Fix Coverity CID 1435957:  Memory - illegal accesses (OVERRUN):

>>> Overrunning array "suffixes" of 7 8-byte elements at element
    index 7 (byte offset 63) using index "idx" (which evaluates to 7).

Note, the biggest input value freq_to_str() can accept is UINT64_MAX,
which is ~18.446 EHz, less than 1000 EHz.

Reported-by: Eduardo Habkost <ehabk...@redhat.com>
Suggested-by: Peter Maydell <peter.mayd...@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org>
---
v3: Follow Peter's suggestion
---
 util/cutils.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/util/cutils.c b/util/cutils.c
index c395974fab4..2f869a843a5 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -891,10 +891,11 @@ char *freq_to_str(uint64_t freq_hz)
     double freq = freq_hz;
     size_t idx = 0;
 
-    while (freq >= 1000.0 && idx < ARRAY_SIZE(suffixes)) {
+    while (freq >= 1000.0) {
         freq /= 1000.0;
         idx++;
     }
+    assert(idx < ARRAY_SIZE(suffixes));
 
     return g_strdup_printf("%0.3g %sHz", freq, suffixes[idx]);
 }
-- 
2.26.2