free prog->aux->used_maps in verifier linux hooks

  o In kernel, it is freed when map itself is freed.
  o This is to avoid sanitizer to report memory leak.

Signed-off-by: Yonghong Song <yhs@plumgrid.com>

README.md

@@ -47,7 +47,7 @@ make headers_install
 ```
 
 For above linux tree, apply the following patch so that llvm can cope with linux
-inline assembly, and workaround a memory leak reporting issue.
+inline assembly:
 
 ```
 yhs@ubuntu:~/work/fuzzer/net-next$ git diff
@@ -64,25 +64,6 @@ index c361593..cacbe0f 100644
  else
  
  # This warning generated too much noise in a regular build.
-diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
-index b074b23..af83c6e 100644
---- a/kernel/bpf/verifier.c
-+++ b/kernel/bpf/verifier.c
-@@ -2186,6 +2186,14 @@ skip_full_check:
-                 * bpf_ld_imm64 instructions
-                 */
-                convert_pseudo_ld_imm64(env);
-+
-+#if 1
-+               /* this is a workaround for userspace verifier.
-+                * in kernel, the env->prog->aux->used_maps will be
-+                * freed when the map itself is freed.
-+                */
-+               kfree(env->prog->aux->used_maps);
-+#endif
-        }
-
- free_log_buf:
 yhs@ubuntu:~/work/fuzzer/net-next$ 
 ```
 

src/helper/linux_hook.c

@@ -801,6 +801,12 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
         if (err >= 0) {
         	/* run eBPF verifier */
 		err = bpf_check(&prog, &attr);
+
+		/* this is a workaround for userspace verifier.
+		 * in kernel, the env->prog->aux->used_maps will be
+		 * freed when the map itself is freed.
+		 */
+		kfree(prog->aux->used_maps);
 	}
         bpf_prog_free_k(prog);
         return err;

src/test/linux-samples-bpf/test_verifier.c

@@ -1009,7 +1009,7 @@ static void usage(char *prog)
 
 int main(int argc, char **argv)
 {
-	if (argc > 0) {
+	if (argc > 1) {
 		if (argc == 3 && strcmp(argv[1], "-g") == 0) {
 			/* generate test cases for fuzzer, no need to run the test */
 			int ret;