linux-kernel - Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk

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Message-ID: <916dbfd3-e601-c4be-41f0-97efc4aaa456@iogearbox.net>
Date:   Tue, 28 Jul 2020 12:53:59 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Peilin Ye <yepeilin.cs@...il.com>,
        Song Liu <songliubraving@...com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        KP Singh <kpsingh@...omium.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent
 kernel-infoleak in xsk_getsockopt()

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@...cle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@...il.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!