On Tue, Feb 26, 2019 at 01:09:30PM +0100, Nicolas Saenz Julienne wrote: > Hi, > as I'm sure most of you are aware of, every URB submission triggers a small > memory allocation in the host controller. For every host controller driver? I thought we had some that did not do that. > On top of that it might be run in > atomic context. This has always seemed to me as a possible source of very hard > to reproduce and potentially nasty issues. For example I'm thinking of embedded > systems driving some critical operation through USB. USB and "critical" should never be in the same sentance, without the word "not" being in there as well. :) > I wonder if anyone has been able to log any failure on that area. I was unable > to find anything on the relevant bugzillas, nor by talking with some > knowledgeable people. Note that some drivers actively protect themselves from > URB submission failures, taking care to resubmit them (see usbhid/hid-core.c). > > Making the allocation fail on some controlled test system seems feasible (it > might not be that easy, it really depends on how realistic you want to be). But > it might be pointless without a real life failure scenario. We have the memory allocation fault system, try using that to see how well we recover (or not) from such failures. Look at how syzbot tested the USB layer, I think they had some scripts/programs that got kind of deep into the driver layers for this type of testing. good luck! greg k-h
