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Subject: Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent
 kernel-infoleak in xsk_getsockopt()
To:     Peilin Ye <yepeilin.cs@gmail.com>,
        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>
Cc:     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>,
        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@vger.kernel.org, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20200728022859.381819-1-yepeilin.cs@gmail.com>
 <20200728053604.404631-1-yepeilin.cs@gmail.com>
From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <916dbfd3-e601-c4be-41f0-97efc4aaa456@iogearbox.net>
Date:   Tue, 28 Jul 2020 12:53:59 +0200
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On 7/28/20 7:36 AM, Peilin Ye 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>
> ---
> Doing `= {};` 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.

I've added above explanation to the commit log since it's useful reasoning for later
on 'why' something has been done a certain way. Applied, thanks Peilin!