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From:   =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>
Date:   Tue, 28 Jul 2020 08:13:05 +0200
Message-ID: <CAJ+HfNhvM8+nfvEC2h+hjR5SGHU7_qyFkNxtiM1yjod6yVB0vQ@mail.gmail.com>
Subject: Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent
 kernel-infoleak in xsk_getsockopt()
To:     Peilin Ye <yepeilin.cs@gmail.com>
Cc:     Song Liu <songliubraving@fb.com>,
        =?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>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        KP Singh <kpsingh@chromium.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        Netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, 28 Jul 2020 at 07:37, Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it.
>
> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> ---

Acked-by: Bj=C3=B6rn T=C3=B6pel <bjorn.topel@intel.com>

> Doing `=3D {};` is sufficient since currently `struct xdp_statistics` is
> defined as follows:
>
> struct xdp_statistics {
>         __u64 rx_dropped;
>         __u64 rx_invalid_descs;
>         __u64 tx_invalid_descs;
>         __u64 rx_ring_full;
>         __u64 rx_fill_ring_empty_descs;
>         __u64 tx_ring_empty_descs;
> };
>
> When being copied to the userspace, `stats` will not contain any
> uninitialized "holes" between struct fields.
>
> Changes in v2:
>     - Remove the "Cc: stable@vger.kernel.org" tag. (Suggested by Song Liu
>       <songliubraving@fb.com>)
>     - Initialize `stats` by assignment instead of using memset().
>       (Suggested by Song Liu <songliubraving@fb.com>)
>
>  net/xdp/xsk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 26e3bba8c204..b2b533eddebf 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -840,7 +840,7 @@ static int xsk_getsockopt(struct socket *sock, int le=
vel, int optname,
>         switch (optname) {
>         case XDP_STATISTICS:
>         {
> -               struct xdp_statistics stats;
> +               struct xdp_statistics stats =3D {};
>                 bool extra_stats =3D true;
>                 size_t stats_size;
>
> --
> 2.25.1
>