linux-kernel - Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

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Message-ID: <CAADnVQ++EF8oEzVvfx=0XHiv_YccHr1gCxzRs5GYGk5uB0CmuQ@mail.gmail.com>
Date:   Wed, 9 Oct 2019 15:49:37 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Ilya Maximets <i.maximets@....org>
Cc:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S . Miller" <davem@...emloft.net>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>
Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

On Wed, Oct 9, 2019 at 9:49 AM Ilya Maximets <i.maximets@....org> wrote:
>
> 'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
> valgrind complain about passing uninitialized stack memory to the
> syscall:
>
>   Syscall param socketcall.setsockopt() points to uninitialised byte(s)
>     at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
>     by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
>   Uninitialised value was created by a stack allocation
>     at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)
>
> Padding bytes appeared after introducing of a new 'flags' field.
> memset() is required to clear them.
>
> Fixes: 10d30e301732 ("libbpf: add flags to umem config")
> Signed-off-by: Ilya Maximets <i.maximets@....org>

Applied. Thanks