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From:   Song Liu <song@kernel.org>
Date:   Mon, 27 Jul 2020 22:07:20 -0700
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Subject: Re: [Linux-kernel-mentees] [PATCH net] xdp: Prevent kernel-infoleak
 in xsk_getsockopt()
To:     Peilin Ye <yepeilin.cs@gmail.com>
Cc:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
        Magnus Karlsson <magnus.karlsson@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
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On Mon, Jul 27, 2020 at 7:30 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it by initializing `stats` with memset().
>
> Cc: stable@vger.kernel.org

8aa5a33578e9 is not in stable branches yet, so we don't need to Cc stable.

> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> ---
>  net/xdp/xsk.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 26e3bba8c204..acf001908a0d 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -844,6 +844,8 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
>                 bool extra_stats = true;
>                 size_t stats_size;
>
> +               memset(&stats, 0, sizeof(stats));
> +

xsk.c doesn't include linux/string.h directly, so using memset may break
build for some config combinations. We can probably just use

struct xdp_statistics stats = {};

Thanks,
Song


>                 if (len < sizeof(struct xdp_statistics_v1)) {
>                         return -EINVAL;
>                 } else if (len < sizeof(stats)) {
> --
> 2.25.1
>