netdev - Re: [PATCH bpf] xsk: fix number of pinned pages/umem size discrepancy

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Date:   Mon, 14 Sep 2020 18:37:08 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        maximmi@...dia.com, "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Ciara Loftus <ciara.loftus@...el.com>
Subject: Re: [PATCH bpf] xsk: fix number of pinned pages/umem size discrepancy

On Thu, Sep 10, 2020 at 12:56 AM Björn Töpel <bjorn.topel@...il.com> wrote:
>
> From: Björn Töpel <bjorn.topel@...el.com>
>
> For AF_XDP sockets, there was a discrepancy between the number of of
> pinned pages and the size of the umem region.
>
> The size of the umem region is used to validate the AF_XDP descriptor
> addresses. The logic that pinned the pages covered by the region only
> took whole pages into consideration, creating a mismatch between the
> size and pinned pages. A user could then pass AF_XDP addresses outside
> the range of pinned pages, but still within the size of the region,
> crashing the kernel.
>
> This change correctly calculates the number of pages to be
> pinned. Further, the size check for the aligned mode is
> simplified. Now the code simply checks if the size is divisible by the
> chunk size.
>
> Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme")
> Reported-by: Ciara Loftus <ciara.loftus@...el.com>
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>

Applied. Thanks