From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf] libbpf: Prevent overriding errno when logging errors
Date: Thu, 13 Aug 2020 22:52:22 +0200 [thread overview]
Message-ID: <87a6yy1d6h.fsf@toke.dk> (raw)
In-Reply-To: <868b8e78-f0ae-8e59-1816-92051acba1f5@iogearbox.net>
Daniel Borkmann <daniel@iogearbox.net> writes:
> On 8/13/20 9:52 PM, Toke Høiland-Jørgensen wrote:
>> Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
>>> On Thu, Aug 13, 2020 at 7:29 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>>>
>>>> Turns out there were a few more instances where libbpf didn't save the
>>>> errno before writing an error message, causing errno to be overridden by
>>>> the printf() return and the error disappearing if logging is enabled.
>>>>
>>>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>>>> ---
>>>
>>> Acked-by: Andrii Nakryiko <andriin@fb.com>
>>>
>>>> tools/lib/bpf/libbpf.c | 12 +++++++-----
>>>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>>>> index 0a06124f7999..fd256440e233 100644
>>>> --- a/tools/lib/bpf/libbpf.c
>>>> +++ b/tools/lib/bpf/libbpf.c
>>>> @@ -3478,10 +3478,11 @@ bpf_object__probe_global_data(struct bpf_object *obj)
>>>>
>>>> map = bpf_create_map_xattr(&map_attr);
>>>> if (map < 0) {
>>>> - cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
>>>> + ret = -errno;
>>>> + cp = libbpf_strerror_r(-ret, errmsg, sizeof(errmsg));
>>>
>>> fyi, libbpf_strerror_r() is smart enough to work with both negative
>>> and positive error numbers (it basically takes abs(err)), so no need
>>> to ensure it's positive here and below.
>>
>> Noted. Although that also means it doesn't hurt either, I suppose; so
>> not going to bother respinning this unless someone insists :)
>
> Fixed up while applying, thanks!
Great, thanks!
-Toke
prev parent reply other threads:[~2020-08-13 20:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-13 14:29 [PATCH bpf] libbpf: Prevent overriding errno when logging errors Toke Høiland-Jørgensen
2020-08-13 16:41 ` Andrii Nakryiko
2020-08-13 19:52 ` Toke Høiland-Jørgensen
2020-08-13 20:35 ` Daniel Borkmann
2020-08-13 20:52 ` Toke Høiland-Jørgensen [this message]
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