sync.c: Do not free an incompleted transfer

Before this patch the code in sync.c would free an incomplete transfer
when libusb_handle_events_completed exits with an error twice in a row.

But we should never free an incomplete transfer, otherwise we may end up
referencing free-ed memory later on.

This patch simply logs an error and keeps on trying until the transfer
completes.

Note that if libusb_handle_events_completed keeps throwing an error the
entire time, without ever completing the transfer, this patch effectively
replaces a potential crash / unspecified behavior, with an endless loop
and logging a ton of errors making clear what is going on.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 8 insertions, 10 deletions

diff --git a/libusb/sync.c b/libusb/sync.c
index e115099..81c13a2 100644
--- a/libusb/sync.c
+++ b/libusb/sync.c
@@ -106,12 +106,11 @@ int API_EXPORTED libusb_control_transfer(libusb_device_handle *dev_handle,
 		if (r < 0) {
 			if (r == LIBUSB_ERROR_INTERRUPTED)
 				continue;
+			usbi_err(HANDLE_CTX(dev_handle),
+				 "libusb_handle_events failed: %s, cancelling transfer and retrying",
+				 libusb_error_name(r));
 			libusb_cancel_transfer(transfer);
-			while (!completed)
-				if (libusb_handle_events_completed(HANDLE_CTX(dev_handle), &completed) < 0)
-					break;
-			libusb_free_transfer(transfer);
-			return r;
+			continue;
 		}
 	}
 
@@ -183,12 +182,11 @@ static int do_sync_bulk_transfer(struct libusb_device_handle *dev_handle,
 		if (r < 0) {
 			if (r == LIBUSB_ERROR_INTERRUPTED)
 				continue;
+			usbi_err(HANDLE_CTX(dev_handle),
+				 "libusb_handle_events failed: %s, cancelling transfer and retrying",
+				 libusb_error_name(r));
 			libusb_cancel_transfer(transfer);
-			while (!completed)
-				if (libusb_handle_events_completed(HANDLE_CTX(dev_handle), &completed) < 0)
-					break;
-			libusb_free_transfer(transfer);
-			return r;
+			continue;
 		}
 	}