Hi, Baolin Wang <baolin.wang@xxxxxxxxxx> writes: > Hi Felipe, > > On 26 May 2016 at 14:22, Felipe Balbi <balbi@xxxxxxxxxx> wrote: >> >> Hi, >> >> Baolin Wang <baolin.wang@xxxxxxxxxx> writes: >>> When handling the endpoint interrupt handler, it maybe disable the endpoint >>> from another core user to set the USB endpoint descriptor pointor to be NULL >>> while issuing usb_gadget_giveback_request() function to release lock. So it >>> will be one bug to check the endpoint type by usb_endpoint_xfer_xxx() APIs with >>> one NULL USB endpoint descriptor. >> >> too complex, Baolin :-) Can you see if this helps: >> >> https://git.kernel.org/cgit/linux/kernel/git/balbi/usb.git/commit/?id=88bf752cfb55e57a78e27c931c9fef63240c739a >> >> The only situation when that can happen is while we drop our lock on >> dwc3_gadget_giveback(). > > OK, But line 1974 and line 2025 as below may be at risk? So I think > can we have a common place to solve the problem in case > usb_endpoint_xfer_xxx() APIs are issued at this risk? What do you > think? Thanks. > > 1956 static int dwc3_cleanup_done_reqs(struct dwc3 *dwc, struct dwc3_ep *dep, > 1957 const struct dwc3_event_depevt *event, int status) > 1958 { > 1959 struct dwc3_request *req; > 1960 struct dwc3_trb *trb; > 1961 unsigned int slot; > 1962 unsigned int i; > 1963 int ret; > 1964 > 1965 do { > 1966 req = next_request(&dep->req_queued); > 1967 if (WARN_ON_ONCE(!req)) > 1968 return 1; > 1969 > 1970 i = 0; > 1971 do { > 1972 slot = req->start_slot + i; > 1973 if ((slot == DWC3_TRB_NUM - 1) && > 1974 usb_endpoint_xfer_isoc(dep->endpoint.desc)) this is executed still with locks held. > 1975 slot++; > 1976 slot %= DWC3_TRB_NUM; > 1977 trb = &dep->trb_pool[slot]; > 1978 > 1979 ret = __dwc3_cleanup_done_trbs(dwc, dep, req, trb, > 1980 event, status); > 1981 if (ret) > 1982 break; > 1983 } while (++i < req->request.num_mapped_sgs); > 1984 > 1985 dwc3_gadget_giveback(dep, req, status); the problem can only show up after this call > 1986 > 1987 if (ret) > 1988 break; > 1989 } while (1); > ....... > > 2011 static void dwc3_endpoint_transfer_complete(struct dwc3 *dwc, > 2012 struct dwc3_ep *dep, const struct dwc3_event_depevt *event) > 2013 { > 2014 unsigned status = 0; > 2015 int clean_busy; > 2016 u32 is_xfer_complete; > 2017 > 2018 is_xfer_complete = (event->endpoint_event == > DWC3_DEPEVT_XFERCOMPLETE); > 2019 > 2020 if (event->status & DEPEVT_STATUS_BUSERR) > 2021 status = -ECONNRESET; > 2022 > 2023 clean_busy = dwc3_cleanup_done_reqs(dwc, dep, event, status); > 2024 if (clean_busy && (is_xfer_complete || > 2025 note the patch I linked you. This is where I added a bail out if the descriptor is NULL. Here's the patch for reference: commit 4d100e870616ccd30cf29abf21d437ec746e1f54 Author: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> Date: Wed May 18 12:37:21 2016 +0300 usb: dwc3: gadget: fix for possible endpoint disable race when we call dwc3_gadget_giveback(), we end up releasing our controller's lock. Another thread could get scheduled and disable the endpoint, subsequently setting dep->endpoint.desc to NULL. In that case, we would end up dereferencing a NULL pointer which would result in a Kernel Oops. Let's avoid the problem by simply returning early if we have a NULL descriptor. Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index f31a59cd5162..3d0573c74b13 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -2019,6 +2019,14 @@ static int dwc3_cleanup_done_reqs(struct dwc3 *dwc, struct dwc3_ep *dep, break; } while (1); + /* + * Our endpoint might get disabled by another thread during + * dwc3_gadget_giveback(). If that happens, we're just gonna return 1 + * early on so DWC3_EP_BUSY flag gets cleared + */ + if (!dep->endpoint.desc) + return 1; + if (usb_endpoint_xfer_isoc(dep->endpoint.desc) && list_empty(&dep->started_list)) { if (list_empty(&dep->pending_list)) { @@ -2085,6 +2093,14 @@ static void dwc3_endpoint_transfer_complete(struct dwc3 *dwc, dwc->u1u2 = 0; } + /* + * Our endpoint might get disabled by another thread during + * dwc3_gadget_giveback(). If that happens, we're just gonna return 1 + * early on so DWC3_EP_BUSY flag gets cleared + */ + if (!dep->endpoint.desc) + return; + if (!usb_endpoint_xfer_isoc(dep->endpoint.desc)) { int ret; Also note that the usb_endpoint_xfer_isoc() call on line 2067 of gadget.c (as in my testing/next from today) won't even get executed, so we're safe there. -- balbi
Attachment:
signature.asc
Description: PGP signature
