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

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Message-ID: <20191012232437.2xpi5mmmv7mxz3yy@ast-mbp.dhcp.thefacebook.com>
Date:   Sat, 12 Oct 2019 16:24:39 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Ilya Maximets <i.maximets@....org>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <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 09, 2019 at 06:49:29PM +0200, Ilya Maximets 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>
> ---
> 
> Version 2:
>   * Struct initializer replaced with explicit memset(). [Andrii]
> 
>  tools/lib/bpf/xsk.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index a902838f9fcc..9d5348086203 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -163,6 +163,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
>  	umem->umem_area = umem_area;
>  	xsk_set_umem_config(&umem->config, usr_config);
>  
> +	memset(&mr, 0, sizeof(mr));
>  	mr.addr = (uintptr_t)umem_area;
>  	mr.len = size;
>  	mr.chunk_size = umem->config.frame_size;

This was already applied. Why did you resend?