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| author | Alan Stern <stern@rowland.harvard.edu> | 2026-09-20 17:37:34 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-10-01 07:16:02 +0200 |
| commit | b263ff9b0fc5c1f371d65c4eb196b31263d039ff (patch) | |
| tree | 83b9d659d9ea919ee2a3fab93f5bb71cadcda166 /drivers/usb | |
| parent | aef5a7e207656ad6abdeeaa0bfc8ee9a1f9c02f6 (diff) | |
| download | linux-stable-b263ff9b0fc5c1f371d65c4eb196b31263d039ff.tar.gz linux-stable-b263ff9b0fc5c1f371d65c4eb196b31263d039ff.zip | |
USB: gadget: dummy-hcd: Fix wait for outstanding request completions
The dummy-hcd driver emulates synchronize_irq() by waiting until its
private callback_usage counter drops to 0 (with the private lock not
held). This counter is incremented whenever a gadget driver callback
occurs (which requires the private lock to be dropped), but not when a
request completion handler is called.
This is an oversight. Request completion is triggered by timer
interrupts (emulating device IRQs in a real UDC), and the interrupt
handlers are supposed to have completed when the synchronize_irq()
emulation routine returns -- they aren't supposed to be in the middle
of a completion callback. If this happens it can lead to a gadget
driver's unbind routine running before all outstanding request
completions have finished, maybe even allowing the gadget driver's
module to be unloaded while a completion handler is still running.
Fix the oversight by incrementing the callback_usage value across
request completion callbacks.
Link: https://lore.kernel.org/linux-usb/7a87e293-633c-4100-aa8d-91560ba5e5c5@rowland.harvard.edu/
Fixes: 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change")
Tested-by: Minseo Kim <neck3922@gmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Link: https://patch.msgid.link/f23b9e1a-f110-441a-a1d8-95f442ec09d5@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
| -rw-r--r-- | drivers/usb/gadget/udc/dummy_hcd.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c index c0e40fa6d..0d30dd67b 100644 --- a/drivers/usb/gadget/udc/dummy_hcd.c +++ b/drivers/usb/gadget/udc/dummy_hcd.c @@ -343,9 +343,11 @@ static void dummy_giveback(struct dummy *dum, struct usb_ep *_ep, { bool fifo = req == &dum->fifo_req; + ++dum->callback_usage; spin_unlock(&dum->lock); usb_gadget_giveback_request(_ep, &req->req); spin_lock(&dum->lock); + --dum->callback_usage; if (fifo) dum->fifo_req_busy = 0; } @@ -759,11 +761,13 @@ static int dummy_queue(struct usb_ep *_ep, struct usb_request *_req, req->req.complete = fifo_complete; list_add_tail(&req->queue, &ep->queue); + ++dum->callback_usage; spin_unlock(&dum->lock); _req->actual = _req->length; _req->status = 0; usb_gadget_giveback_request(_ep, _req); spin_lock(&dum->lock); + --dum->callback_usage; } else list_add_tail(&req->queue, &ep->queue); spin_unlock_irqrestore(&dum->lock, flags); |