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    Subject[PATCH 5.18 025/339] usb: dwc3: gadget: Replace list_for_each_entry_safe() if using giveback
    Date
    From: Wesley Cheng <quic_wcheng@quicinc.com>

    [ Upstream commit bf594d1d0c1d7b895954018043536ffd327844f9 ]

    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

    Fixes: d4f1afe5e896 ("usb: dwc3: gadget: move requests to cancelled_list")
    Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
    Link: https://lore.kernel.org/r/20220414183521.23451-1-quic_wcheng@quicinc.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/usb/dwc3/gadget.c | 20 ++++++++++++++++----
    1 file changed, 16 insertions(+), 4 deletions(-)

    diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
    index 026fc360cc50..6936d8ce8981 100644
    --- a/drivers/usb/dwc3/gadget.c
    +++ b/drivers/usb/dwc3/gadget.c
    @@ -2001,10 +2001,10 @@ static void dwc3_gadget_ep_skip_trbs(struct dwc3_ep *dep, struct dwc3_request *r
    static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep)
    {
    struct dwc3_request *req;
    - struct dwc3_request *tmp;
    struct dwc3 *dwc = dep->dwc;

    - list_for_each_entry_safe(req, tmp, &dep->cancelled_list, list) {
    + while (!list_empty(&dep->cancelled_list)) {
    + req = next_request(&dep->cancelled_list);
    dwc3_gadget_ep_skip_trbs(dep, req);
    switch (req->status) {
    case DWC3_REQUEST_STATUS_DISCONNECTED:
    @@ -2021,6 +2021,12 @@ static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep)
    dwc3_gadget_giveback(dep, req, -ECONNRESET);
    break;
    }
    + /*
    + * The endpoint is disabled, let the dwc3_remove_requests()
    + * handle the cleanup.
    + */
    + if (!dep->endpoint.desc)
    + break;
    }
    }

    @@ -3333,15 +3339,21 @@ static void dwc3_gadget_ep_cleanup_completed_requests(struct dwc3_ep *dep,
    const struct dwc3_event_depevt *event, int status)
    {
    struct dwc3_request *req;
    - struct dwc3_request *tmp;

    - list_for_each_entry_safe(req, tmp, &dep->started_list, list) {
    + while (!list_empty(&dep->started_list)) {
    int ret;

    + req = next_request(&dep->started_list);
    ret = dwc3_gadget_ep_cleanup_completed_request(dep, event,
    req, status);
    if (ret)
    break;
    + /*
    + * The endpoint is disabled, let the dwc3_remove_requests()
    + * handle the cleanup.
    + */
    + if (!dep->endpoint.desc)
    + break;
    }
    }

    --
    2.35.1


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