On Saturday 09 May 2009 21:29:59 Greg KH wrote: > On Sat, May 09, 2009 at 12:29:27PM -0500, Larry Finger wrote: > > I think there is a second problem that John's fix does not treat. Although the > > buffer is removed from the stack, there is no assurance that the buffer obtained > > with kmalloc() is reachable by DMA. This case will be triggered if the USB > > adapter does 32-bit DMA and the system has more than 4 GB RAM. In practice this does not hit, because such systems' kmalloc does not return memory above 4G (i386) _or_ the DMA mapping functions take care of bounce buffering or I/O-remapping (should be true for all other arches). So if the device is able to do DMA with addresses >=32bit it should be fine, provided it correctly sets the DMA mask. > Memory returned by kmalloc will always be able to be DMAable. If not, > we have lots of problems :) True for sane devices. False for devices like Broadcom HND-DMA, which should only be used to slap thy hw engineers. -- Greetings, Michael. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
