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    Subject[patch 23/60] e1000: add missing length check to e1000 receive routine
    -stable review patch.  If anyone has any objections, please let us know.

    From: Neil Horman <>

    commit ea30e11970a96cfe5e32c03a29332554573b4a10 upstream.

    Patch to fix bad length checking in e1000. E1000 by default does two

    1) Spans rx descriptors for packets that don't fit into 1 skb on recieve
    2) Strips the crc from a frame by subtracting 4 bytes from the length prior to
    doing an skb_put

    Since the e1000 driver isn't written to support receiving packets that span
    multiple rx buffers, it checks the End of Packet bit of every frame, and
    discards it if its not set. This places us in a situation where, if we have a
    spanning packet, the first part is discarded, but the second part is not (since
    it is the end of packet, and it passes the EOP bit test). If the second part of
    the frame is small (4 bytes or less), we subtract 4 from it to remove its crc,
    underflow the length, and wind up in skb_over_panic, when we try to skb_put a
    huge number of bytes into the skb. This amounts to a remote DOS attack through
    careful selection of frame size in relation to interface MTU. The fix for this
    is already in the e1000e driver, as well as the e1000 sourceforge driver, but no
    one ever pushed it to e1000. This is lifted straight from e1000e, and prevents
    small frames from causing the underflow described above

    Signed-off-by: Neil Horman <>
    Tested-by: Andy Gospodarek <>
    Signed-off-by: David S. Miller <>
    Signed-off-by: Greg Kroah-Hartman <>

    drivers/net/e1000/e1000_main.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/drivers/net/e1000/e1000_main.c
    +++ b/drivers/net/e1000/e1000_main.c
    @@ -4133,8 +4133,9 @@ static bool e1000_clean_rx_irq(struct e1

    length = le16_to_cpu(rx_desc->length);
    - if (unlikely(!(status & E1000_RXD_STAT_EOP))) {
    + /* !EOP means multiple descriptors were used to store a single
    + * packet, also make sure the frame isn't just CRC only */
    + if (unlikely(!(status & E1000_RXD_STAT_EOP) || (length <= 4))) {
    /* All receives must fit into a single buffer */
    E1000_DBG("%s: Receive packet consumed multiple"
    " buffers\n", netdev->name);

     \ /
      Last update: 2009-06-10 05:41    [W:0.023 / U:2.452 seconds]
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