On Wed, Aug 11, 2021 at 08:57:12PM +0100, Sudip Mukherjee wrote:
Hi Greg,
On Mon, Aug 09, 2021 at 10:48:22AM +0200, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Here is the backport, will also apply to 5.4-stable and 4.19-stable.
-- Regards Sudip
From e01c2051bac15d89168e30c2cfa2cd828104ed4d Mon Sep 17 00:00:00 2001
From: Wesley Cheng wcheng@codeaurora.org Date: Thu, 29 Jul 2021 00:33:14 -0700 Subject: [PATCH] usb: dwc3: gadget: Use list_replace_init() before traversing lists
commit d25d85061bd856d6be221626605319154f9b5043 upstream
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@codeauror... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [sudip: adjust context] Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com
drivers/usb/dwc3/gadget.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)
This breaks systems, and is reverted in my tree and will be sent to Linus later today (the revert), so I'll drop this from the stable trees for now.
thanks,
greg k-h