netdev - Re: [PATCH bpf-next v2 2/4] xsk: add proper barriers and {READ, WRITE}

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Date:   Mon, 26 Aug 2019 10:54:34 -0700
From:   "Jonathan Lemon" <jonathan.lemon@...il.com>
To:     "Björn Töpel" <bjorn.topel@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        "Björn Töpel" <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        bpf@...r.kernel.org,
        syzbot+c82697e3043781e08802@...kaller.appspotmail.com,
        hdanton@...a.com, i.maximets@...sung.com
Subject: Re: [PATCH bpf-next v2 2/4] xsk: add proper barriers and {READ,
 WRITE}_ONCE-correctness for state



On 25 Aug 2019, at 23:10, Björn Töpel wrote:

> From: Björn Töpel <bjorn.topel@...el.com>
>
> The state variable was read, and written outside the control mutex
> (struct xdp_sock, mutex), without proper barriers and {READ,
> WRITE}_ONCE correctness.
>
> In this commit this issue is addressed, and the state member is now
> used a point of synchronization whether the socket is setup correctly
> or not.
>
> This also fixes a race, found by syzcaller, in xsk_poll() where umem
> could be accessed when stale.
>
> Suggested-by: Hillf Danton <hdanton@...a.com>
> Reported-by: syzbot+c82697e3043781e08802@...kaller.appspotmail.com
> Fixes: 77cd0d7b3f25 ("xsk: add support for need_wakeup flag in AF_XDP 
> rings")
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>

Acked-by: Jonathan Lemon <jonathan.lemon@...il.com>