On Fri, Apr 27, 2007 at 10:49:32PM +0100, Alan Cox wrote:
(please CC: me on patches that I submitted, I missed this...)
> Unless there is something I'm missing most of these patches seem totally
> unsafe.
Hm, no, they were using a lock that was never being used by the core,
thereby protecting nothing.
> > --- a/drivers/usb/core/devices.c
> > +++ b/drivers/usb/core/devices.c
> > @@ -246,7 +246,6 @@ static char *usb_dump_interface_descriptor(char *start,
> > char *end,
> >
> > if (start > end)
> > return start;
> > - down_read(&usb_bus_type.subsys.rwsem);
> > if (iface) {
> > driver_name = (iface->dev.driver
> > ? iface->dev.driver->name
>
> iface->dev.driver can now become NULL during the evaluation above
All of the USB stuff is already covered by a different lock, see the
linux-usb-devel list for when I originally proposed this patch (also
CC:ed to verify I didn't miss anything...)
> > @@ -444,8 +441,6 @@ static int releaseintf(struct dev_state *ps, unsigned
> > int ifnum)
> > if (ifnum >= 8*sizeof(ps->ifclaimed))
> > return err;
> > dev = ps->dev;
> > - /* lock against other changes to driver bindings */
> > - down_write(&usb_bus_type.subsys.rwsem);
> > intf = usb_ifnum_to_if(dev, ifnum);
> > if (!intf)
> > err = -ENOENT;
> > @@ -453,7 +448,6 @@ static int releaseintf(struct dev_state *ps, unsigned
> > int ifnum)
> > usb_driver_release_interface(&usbfs_driver, intf);
>
> Which takes iface->dev.driver to NULL
>
> > err = 0;
> > }
> > - up_write(&usb_bus_type.subsys.rwsem);
> > return err;
> > }
> >
> > @@ -813,7 +807,6 @@ static int proc_getdriver(struct dev_state *ps, void
> > __user *arg)
> >
> > if (copy_from_user(&gd, arg, sizeof(gd)))
> > return -EFAULT;
> > - down_read(&usb_bus_type.subsys.rwsem);
> > intf = usb_ifnum_to_if(ps->dev, gd.interface);
> > if (!intf || !intf->dev.driver)
> > ret = -ENODATA;
>
> Ditto ...
thanks,
greg k-h
-
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