It's perfectly possible to have no function symbols in your elf file
and if we do the undefined behaviour sanitizer rightly complains about
us passing NULL to qsort. Check nsyms before we go ahead.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/elf_ops.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
index a1411bfcab6..b5d4074d1e3 100644
--- a/include/hw/elf_ops.h
+++ b/include/hw/elf_ops.h
@@ -170,8 +170,13 @@ static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab,
         }
         i++;
     }
-    syms = g_realloc(syms, nsyms * sizeof(*syms));
 
+    /* check we have symbols left */
+    if (nsyms == 0) {
+        goto fail;
+    }
+
+    syms = g_realloc(syms, nsyms * sizeof(*syms));
     qsort(syms, nsyms, sizeof(*syms), glue(symcmp, SZ));
     for (i = 0; i < nsyms - 1; i++) {
         if (syms[i].st_size == 0) {
-- 
2.20.1