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libusb: fix race condition on device close #189

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merged 1 commit into from
Oct 14, 2020
Merged

libusb: fix race condition on device close #189

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18 changes: 10 additions & 8 deletions libusb/hid.c
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Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,7 @@ struct hid_device_ {
pthread_cond_t condition;
pthread_barrier_t barrier; /* Ensures correct startup sequence */
int shutdown_thread;
int cancelled;
int transfer_loop_finished;
struct libusb_transfer *transfer;

/* List of received input reports. */
Expand Down Expand Up @@ -772,13 +772,9 @@ static void read_callback(struct libusb_transfer *transfer)
}
else if (transfer->status == LIBUSB_TRANSFER_CANCELLED) {
dev->shutdown_thread = 1;
dev->cancelled = 1;
return;
}
else if (transfer->status == LIBUSB_TRANSFER_NO_DEVICE) {
dev->shutdown_thread = 1;
dev->cancelled = 1;
return;
}
else if (transfer->status == LIBUSB_TRANSFER_TIMED_OUT) {
//LOG("Timeout (normal)\n");
Expand All @@ -787,12 +783,17 @@ static void read_callback(struct libusb_transfer *transfer)
LOG("Unknown transfer code: %d\n", transfer->status);
}

if (dev->shutdown_thread) {
dev->transfer_loop_finished = 1;
return;
}

/* Re-submit the transfer object. */
res = libusb_submit_transfer(transfer);
if (res != 0) {
LOG("Unable to submit URB. libusb error code: %d\n", res);
dev->shutdown_thread = 1;
dev->cancelled = 1;
dev->transfer_loop_finished = 1;
}
}

Expand Down Expand Up @@ -835,6 +836,7 @@ static void *read_thread(void *param)
res != LIBUSB_ERROR_TIMEOUT &&
res != LIBUSB_ERROR_OVERFLOW &&
res != LIBUSB_ERROR_INTERRUPTED) {
dev->shutdown_thread = 1;
break;
}
}
Expand All @@ -844,8 +846,8 @@ static void *read_thread(void *param)
if no transfers are pending, but that's OK. */
libusb_cancel_transfer(dev->transfer);

while (!dev->cancelled)
libusb_handle_events_completed(usb_context, &dev->cancelled);
while (!dev->transfer_loop_finished)
libusb_handle_events_completed(usb_context, &dev->transfer_loop_finished);

/* Now that the read thread is stopping, Wake any threads which are
waiting on data (in hid_read_timeout()). Do this under a mutex to
Expand Down