https://github.com/torvalds/linux
Revision d25d85061bd856d6be221626605319154f9b5043 authored by Wesley Cheng on 29 July 2021, 07:33:14 UTC, committed by Greg Kroah-Hartman on 05 August 2021, 09:01:34 UTC
The list_for_each_entry_safe() macro saves the current item (n) and the item after (n+1), so that n can be safely removed without corrupting the list. However, when traversing the list and removing items using gadget giveback, the DWC3 lock is briefly released, allowing other routines to execute. There is a situation where, while items are being removed from the cancelled_list using dwc3_gadget_ep_cleanup_cancelled_requests(), the pullup disable routine is running in parallel (due to UDC unbind). As the cleanup routine removes n, and the pullup disable removes n+1, once the cleanup retakes the DWC3 lock, it references a request who was already removed/handled. With list debug enabled, this leads to a panic. Ensure all instances of the macro are replaced where gadget giveback is used. Example call stack: Thread#1: __dwc3_gadget_ep_set_halt() - CLEAR HALT -> dwc3_gadget_ep_cleanup_cancelled_requests() ->list_for_each_entry_safe() ->dwc3_gadget_giveback(n) ->dwc3_gadget_del_and_unmap_request()- n deleted[cancelled_list] ->spin_unlock ->Thread#2 executes ... ->dwc3_gadget_giveback(n+1) ->Already removed! Thread#2: dwc3_gadget_pullup() ->waiting for dwc3 spin_lock ... ->Thread#1 released lock ->dwc3_stop_active_transfers() ->dwc3_remove_requests() ->fetches n+1 item from cancelled_list (n removed by Thread#1) ->dwc3_gadget_giveback() ->dwc3_gadget_del_and_unmap_request()- n+1 deleted[cancelled_list] ->spin_unlock Fix this condition by utilizing list_replace_init(), and traversing through a local copy of the current elements in the endpoint lists. This will also set the parent list as empty, so if another thread is also looping through the list, it will be empty on the next iteration. Fixes: d4f1afe5e896 ("usb: dwc3: gadget: move requests to cancelled_list") Cc: stable <stable@vger.kernel.org> Acked-by: Felipe Balbi <balbi@kernel.org> Signed-off-by: Wesley Cheng <wcheng@codeaurora.org> Link: https://lore.kernel.org/r/1627543994-20327-1-git-send-email-wcheng@codeaurora.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 parent b47b0b6
Tip revision: d25d85061bd856d6be221626605319154f9b5043 authored by Wesley Cheng on 29 July 2021, 07:33:14 UTC
usb: dwc3: gadget: Use list_replace_init() before traversing lists
usb: dwc3: gadget: Use list_replace_init() before traversing lists
Tip revision: d25d850
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