On 25-01-22 10:59:33, Alan Stern wrote: > On Wed, Jan 22, 2025 at 05:20:12AM -0800, Nikita Zhandarovich wrote: > > Hi, > > > > On 1/22/25 04:43, Petko Manolov wrote: > > > On 25-01-22 02:42:46, Nikita Zhandarovich wrote: > > >> Syzkaller reports [1] encountering a common issue of utilizing a wrong usb > > >> endpoint type during URB submitting stage. This, in turn, triggers a warning > > >> shown below. > > > > > > If these endpoints were of the wrong type the driver simply wouldn't work. > > Better not to bind at all than to bind in a non-working way. Especially when > we can tell by a simple check that the device isn't what the driver expects. > > > > The proposed change in the patch doesn't do much in terms of fixing the > > > issue (pipe 3 != type 1) and if usb_check_bulk_endpoints() fails, the > > > driver will just not probe successfully. I don't see how this is an > > > improvement to the current situation. > > It fixes the issue by preventing the driver from submitting an interrupt URB > to a bulk endpoint or vice versa. I always thought that once DID/VID is verified, there's no much room for that to happen. > > > We should either spend some time fixing the "BOGUS urb xfer, pipe 3 != > > > type 1" for real or not touch anything. > > > > > > > > > Petko > > > > > > > > > > Thank you for your answer, I had a couple thoughts though. > > > > If I understand correctly (which may not be the case, of course), since the > > driver currently does not have any sanity checks for endpoints and URBs' > > pipes are initialized essentially by fixed constants (as is often the case), > > once again without any testing, then a virtual, weirdly constructed device, > > like the one made up by Syzkaller, could provide endpoints with contents > > that may cause that exact warning. > > > > Real-life devices (with appropriate eps) would still work well and are in no > > danger, with or without the patch. And even if that warning is triggered, I > > am not certain the consequences are that severe, maybe on kernels with > > 'panic_on_warn' set, and that's another conversation. However, it seems that > > the change won't hurt either. Failing probe() in such situations looks to be > > the standard. > > > > If my approach is flawed, I'd really appreciate some hints on how you would > > address that issue and I'd like to tackle it. I'd also ask if other > > recipients could provide some of their views on the issue, even if just to > > prove me wrong. > > I agree with this approach; it seems like the best way to address this issue. Alright then. I'd recommend following Fedor Pchelkin's advise about moving those declarations to the beginning of probe(), though. Petko
