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    SubjectRe: [Xen-devel] [PATCH] drivers: net: xen-netfront: fix array initialization bug
    On 14/04/14 17:51, David Miller wrote:
    > From: David Vrabel <david.vrabel@citrix.com>
    > Date: Mon, 14 Apr 2014 10:42:20 +0100
    >
    >> On 12/04/14 21:51, David Miller wrote:
    >>> From: Vincenzo Maffione <v.maffione@gmail.com>
    >>> Date: Sat, 12 Apr 2014 11:55:40 +0200
    >>>
    >>>> This patch fixes the initialization of an array used in the TX
    >>>> datapath that was mistakenly initialized together with the
    >>>> RX datapath arrays. An out of range array access could happen
    >>>> when RX and TX rings had different sizes.
    >>>>
    >>>> Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
    >>>
    >>> Good catch, applied, thanks.
    >>
    >> Thanks. You can queue this for net-next since the Tx and Rx rings are
    >> the same constant size.
    >
    > I was able to determine when I reviewed this patch that the size in bytes
    > of the rings are the same (PAGE_SIZE), but I couldn't ascertain whether
    > the individual ring entries in the TX ring and RX ring are the same size.
    >
    > Are they?

    Yes. It's not at all obvious, but each ends up with 256 entries.

    Tx entries are 12 bytes and Rx entries are 8 bytes. The ring macros
    reserve some space in the shared page for the producer/consumer indexes
    /and/ round down the number to the next power of two.

    David



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