[PATCH 3/4] tools: bpftool: fix potential NULL pointer dereference in do_load

[Wen Yang <wen.yang99@zte.com.cn>]

This patch fixes a possible null pointer dereference in
do_load, detected by the semantic patch
deref_null.cocci, with the following warning:

./tools/bpf/bpftool/prog.c:1021:23-25: ERROR: map_replace is NULL but dereferenced.

The following code has potential null pointer references:
 881             map_replace = reallocarray(map_replace, old_map_fds + 1,
 882                                        sizeof(*map_replace));
 883             if (!map_replace) {
 884                     p_err("mem alloc failed");
 885                     goto err_free_reuse_maps;
 886             }

...
1019 err_free_reuse_maps:
1020         for (i = 0; i < old_map_fds; i++)
1021                 close(map_replace[i].fd);
1022         free(map_replace);

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Reviewed-by: Tan Hu <tan.hu@zte.com.cn>
CC: Julia Lawall <julia.lawall@lip6.fr>
---
 tools/bpf/bpftool/prog.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 5302ee2..de42187 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -1017,8 +1017,9 @@ static int do_load(int argc, char **argv)
 err_close_obj:
 	bpf_object__close(obj);
 err_free_reuse_maps:
-	for (i = 0; i < old_map_fds; i++)
-		close(map_replace[i].fd);
+	if (map_replace)
+		for (i = 0; i < old_map_fds; i++)
+			close(map_replace[i].fd);
 	free(map_replace);
 	return -1;
 }
-- 
2.9.5