netdev - [PATCH bpf-next 2/2] bpftool: Fix error check when calling hashmap_

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Date:   Fri,  7 Jan 2022 10:26:20 -0500
From:   Mauricio Vásquez <mauricio@...volk.io>
To:     netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Quentin Monnet <quentin@...valent.com>
Subject: [PATCH bpf-next 2/2] bpftool: Fix error check when calling hashmap__new()

hashmap__new() encodes errors with ERR_PTR(), hence it's not valid to
check the returned pointer against NULL and IS_ERR() has to be used
instead.

libbpf_get_error() can't be used in this case as hashmap__new() is not
part of the public libbpf API and it'll continue using ERR_PTR() after
libbpf 1.0.

Fixes: 8f184732b60b ("bpftool: Switch to libbpf's hashmap for pinned paths of BPF objects")
Fixes: 2828d0d75b73 ("bpftool: Switch to libbpf's hashmap for programs/maps in BTF listing")
Fixes: d6699f8e0f83 ("bpftool: Switch to libbpf's hashmap for PIDs/names references")

Signed-off-by: Mauricio Vásquez <mauricio@...volk.io>
---
 tools/bpf/bpftool/btf.c  | 2 +-
 tools/bpf/bpftool/link.c | 3 ++-
 tools/bpf/bpftool/map.c  | 2 +-
 tools/bpf/bpftool/pids.c | 3 ++-
 tools/bpf/bpftool/prog.c | 2 +-
 5 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 59833125ac0a..a2c665beda87 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -902,7 +902,7 @@ static int do_show(int argc, char **argv)
 				      equal_fn_for_key_as_id, NULL);
 	btf_map_table = hashmap__new(hash_fn_for_key_as_id,
 				     equal_fn_for_key_as_id, NULL);
-	if (!btf_prog_table || !btf_map_table) {
+	if (IS_ERR(btf_prog_table) || IS_ERR(btf_map_table)) {
 		hashmap__free(btf_prog_table);
 		hashmap__free(btf_map_table);
 		if (fd >= 0)
diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 2c258db0d352..97dec81950e5 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -2,6 +2,7 @@
 /* Copyright (C) 2020 Facebook */
 
 #include <errno.h>
+#include <linux/err.h>
 #include <net/if.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -306,7 +307,7 @@ static int do_show(int argc, char **argv)
 	if (show_pinned) {
 		link_table = hashmap__new(hash_fn_for_key_as_id,
 					  equal_fn_for_key_as_id, NULL);
-		if (!link_table) {
+		if (IS_ERR(link_table)) {
 			p_err("failed to create hashmap for pinned paths");
 			return -1;
 		}
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index cc530a229812..c66a3c979b7a 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -699,7 +699,7 @@ static int do_show(int argc, char **argv)
 	if (show_pinned) {
 		map_table = hashmap__new(hash_fn_for_key_as_id,
 					 equal_fn_for_key_as_id, NULL);
-		if (!map_table) {
+		if (IS_ERR(map_table)) {
 			p_err("failed to create hashmap for pinned paths");
 			return -1;
 		}
diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c
index 56b598eee043..7c384d10e95f 100644
--- a/tools/bpf/bpftool/pids.c
+++ b/tools/bpf/bpftool/pids.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 /* Copyright (C) 2020 Facebook */
 #include <errno.h>
+#include <linux/err.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -101,7 +102,7 @@ int build_obj_refs_table(struct hashmap **map, enum bpf_obj_type type)
 	libbpf_print_fn_t default_print;
 
 	*map = hashmap__new(hash_fn_for_key_as_id, equal_fn_for_key_as_id, NULL);
-	if (!*map) {
+	if (IS_ERR(*map)) {
 		p_err("failed to create hashmap for PID references");
 		return -1;
 	}
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 2a21d50516bc..33ca834d5f51 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -641,7 +641,7 @@ static int do_show(int argc, char **argv)
 	if (show_pinned) {
 		prog_table = hashmap__new(hash_fn_for_key_as_id,
 					  equal_fn_for_key_as_id, NULL);
-		if (!prog_table) {
+		if (IS_ERR(prog_table)) {
 			p_err("failed to create hashmap for pinned paths");
 			return -1;
 		}
-- 
2.25.1