linux-kernel - Re: [PATCH] bpftool: Fix NULL vs IS_ERR() checking for return value of hashmap_

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Date:   Mon, 13 Dec 2021 11:33:00 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     林妙倩 <linmq006@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpftool: Fix NULL vs IS_ERR() checking for return value
 of hashmap__new

On Mon, Dec 13, 2021 at 7:07 AM 林妙倩 <linmq006@...il.com> wrote:
>
> Sorry, I forgot to do compile testing. I will test it and let you know.
>
> Miaoqian Lin <linmq006@...il.com> 于2021年12月12日周日 13:18写道：
>>
>> The hashmap__new() function does not return NULL on errors. It returns
>> ERR_PTR(-ENOMEM). Using IS_ERR() to check the return value to fix this.
>>
>> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
>> ---

Please do test (not just compile test) and re-send all three patches
as one patch set instead of three independent patches. Thanks.


>>  tools/bpf/bpftool/link.c | 2 +-
>>  tools/bpf/bpftool/map.c  | 2 +-
>>  tools/bpf/bpftool/pids.c | 2 +-
>>  3 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
>> index 2c258db0d352..0dc402a89cd8 100644
>> --- a/tools/bpf/bpftool/link.c
>> +++ b/tools/bpf/bpftool/link.c
>> @@ -306,7 +306,7 @@ 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 cae1f1119296..af83ae37d247 100644
>> --- a/tools/bpf/bpftool/map.c
>> +++ b/tools/bpf/bpftool/map.c
>> @@ -698,7 +698,7 @@ 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..6c4767e97061 100644
>> --- a/tools/bpf/bpftool/pids.c
>> +++ b/tools/bpf/bpftool/pids.c
>> @@ -101,7 +101,7 @@ 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;
>>         }
>> --
>> 2.17.1
>>