newbus flaw

From: Dag-Erling Smørgrav (des_at_des.no)
Date: 05/11/04

  • Next message: Doug Rabson: "Re: newbus flaw" 
    To: arch@freebsd.org
Date: Tue, 11 May 2004 16:39:40 +0200

    I've found what I believe is a serious flaw in newbus.

    When a driver that has a DEVICE_IDENTIFY method is loaded, the
    identify method is called. If it finds supported hardware, it uses
    BUS_ADD_CHILD to notify the parent bus of the presence of that
    hardware. At some later point, during a bus rescan, the attach
    routine is called for each device that was identified in this manner.

    When the driver is unloaded, the device is detached, but it remains on
    the bus's list of child devices. The next time the module is loaded,
    its DEVICE_IDENTIFY method is called again, and incorrectly adds a
    second child device to the bus, because it does not know that one
    already exists.

    There is no way for DEVICE_IDENTIFY to check if a matching child
    already exists on the bus, or for the module's event handler to unlist
    the child when unloading.

    The first time you load the module, you get foo0; the second time, you
    get foo0 *and* foo1 referencing the same physical device; the third
    time, you get foo0, foo1, and foo2, etc.

    I've also seen something similar happen when multiple ndis drivers are
    loaded; the first one re-attaches to the hardware when the second one
    is loaded.

    DES 

    -- 
Dag-Erling Smørgrav - des@des.no
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