From: Song Liu <songliubraving@fb.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Ian Rogers <irogers@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, Martin Lau <kafai@fb.com>,
"Yonghong Song" <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] libbpf hashmap: Fix undefined behavior in hash_bits
Date: Thu, 29 Oct 2020 22:57:42 +0000 [thread overview]
Message-ID: <8A7F0E86-9A11-4ED9-AE8A-881A5A260DB7@fb.com> (raw)
In-Reply-To: <CAEf4BzaX4KT5tOn9gSR24OtrX8MT3yW2yfTq244ewnRouWDJdA@mail.gmail.com>
> On Oct 29, 2020, at 3:38 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Thu, Oct 29, 2020 at 3:38 PM Ian Rogers <irogers@google.com> wrote:
>>
>> If bits is 0, the case when the map is empty, then the >> is the size of
>> the register which is undefined behavior - on x86 it is the same as a
>> shift by 0. Fix by handling the 0 case explicitly and guarding calls to
>> hash_bits for empty maps in hashmap__for_each_key_entry and
>> hashmap__for_each_entry_safe.
>>
>> Suggested-by: Andrii Nakryiko <andriin@fb.com>,
>> Signed-off-by: Ian Rogers <irogers@google.com>
>> ---
>
> Looks good. Thanks and sorry for unnecessary iterations.
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
prev parent reply other threads:[~2020-10-29 22:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-29 22:37 [PATCH v2] libbpf hashmap: Fix undefined behavior in hash_bits Ian Rogers
2020-10-29 22:38 ` Andrii Nakryiko
2020-10-29 22:57 ` Song Liu [this message]
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