netdev - Re: [PATCH bpf-next] xsk: Init all ring members in xsk_umem__create and xsk_socket_

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Message-ID: <ae371400-e37f-bbac-691e-cc50235f1ee0@iogearbox.net>
Date:   Sat, 28 Mar 2020 18:14:25 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Magnus Karlsson <magnus.karlsson@...il.com>,
        Fletcher Dunn <fletcherd@...vesoftware.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Brandon Gilmore <bgilmore@...vesoftware.com>,
        Steven Noonan <steven@...vesoftware.com>
Subject: Re: [PATCH bpf-next] xsk: Init all ring members in xsk_umem__create
 and xsk_socket__create

On 3/28/20 10:18 AM, Magnus Karlsson wrote:
> On Fri, Mar 27, 2020 at 4:40 AM Fletcher Dunn
> <fletcherd@...vesoftware.com> wrote:
>>
>> Fix a sharp edge in xsk_umem__create and xsk_socket__create.  Almost all of
>> the members of the ring buffer structs are initialized, but the "cached_xxx"
>> variables are not all initialized.  The caller is required to zero them.
>> This is needlessly dangerous.  The results if you don't do it can be very bad.
>> For example, they can cause xsk_prod_nb_free and xsk_cons_nb_avail to return
>> values greater than the size of the queue.  xsk_ring_cons__peek can return an
>> index that does not refer to an item that has been queued.
>>
>> I have confirmed that without this change, my program misbehaves unless I
>> memset the ring buffers to zero before calling the function.  Afterwards,
>> my program works without (or with) the memset.
> 
> Thank you Flecther for catching this. Appreciated.
> 
> /Magnus
> 
> Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>

Applied, thanks!