bpftool: Properly close va_list 'ap' by va_end() on error

stable inclusion
from stable-5.10.53
commit 782d71e29b2960b0027aca046cd0077998cb54d9
bugzilla: 175574 https://gitee.com/openeuler/kernel/issues/I4DTUX

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=782d71e29b2960b0027aca046cd0077998cb54d9

--------------------------------

commit bc832065 upstream.

va_list 'ap' was opened but not closed by va_end() in error case. It should
be closed by va_end() before the return.

Fixes: aa52bcbe ("tools: bpftool: Fix json dump crash on powerpc")
Signed-off-by: NGu Shengxian <gushengxian@yulong.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/bpf/20210706013543.671114-1-gushengxian507419@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

tools/bpf/bpftool/jit_disasm.c

@@ -43,11 +43,13 @@ static int fprintf_json(void *out, const char *fmt, ...)
 {
 	va_list ap;
 	char *s;
+	int err;
 
 	va_start(ap, fmt);
-	if (vasprintf(&s, fmt, ap) < 0)
-		return -1;
+	err = vasprintf(&s, fmt, ap);
 	va_end(ap);
+	if (err < 0)
+		return -1;
 
 	if (!oper_count) {
 		int i;