[PATCH] usb: atm: use request_firmware_direct() for firmware probing

[Matvey Valigura <valigurasm@gmail.com>]

When disconnecting a device while firmware is not present on the system,
usbatm_usb_disconnect() waits for the heavy_init thread to finish:
    wait_for_completion(&instance->thread_exited);

If CONFIG_FW_LOADER_USER_HELPER_FALLBACK is enabled, missing firmware
causes request_firmware() to fall back to sysfs/udevd. This creates a
circular dependency during disconnect:
1. usb_disconnect() holds device_lock(&udev->dev).
2. usbatm_usb_disconnect() waits for instance->thread to exit.
3. instance->thread waits for request_firmware() sysfs fallback.
4. udevd receives the firmware uevent and attempts to read sysfs
   attributes (e.g. serial), blocking on device_lock(&udev->dev).

Furthermore, the fallback wait uses wait_for_completion_killable_timeout(),
which ignores the non-fatal SIGTERM signal sent by usbatm_usb_disconnect().
Because speedtch and cxacru probe multiple candidate firmware files
sequentially, each file stalls for the 60-second fallback timeout,
triggering hung task timeouts (>120s) reported by syzbot.

Switch to request_firmware_direct() to probe firmware files directly from
the filesystem without falling back to user-mode helper.

Reported-by: syzbot+9ca2c9f85bd8b5e46516@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9ca2c9f85bd8b5e46516
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Matvey Valigura <valigurasm@gmail.com>
---
 drivers/usb/atm/cxacru.c   | 2 +-
 drivers/usb/atm/speedtch.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/atm/cxacru.c b/drivers/usb/atm/cxacru.c
index 636f7886f..7d1944487 100644
--- a/drivers/usb/atm/cxacru.c
+++ b/drivers/usb/atm/cxacru.c
@@ -993,7 +993,7 @@ static int cxacru_find_firmware(struct cxacru_data *instance,
 	sprintf(buf, "cxacru-%s.bin", phase);
 	usb_dbg(usbatm, "cxacru_find_firmware: looking for %s\n", buf);
 
-	if (request_firmware(fw_p, buf, dev)) {
+	if (request_firmware_direct(fw_p, buf, dev)) {
 		usb_dbg(usbatm, "no stage %s firmware found\n", phase);
 		return -ENOENT;
 	}
diff --git a/drivers/usb/atm/speedtch.c b/drivers/usb/atm/speedtch.c
index 9d28c652b..c82db2f7a 100644
--- a/drivers/usb/atm/speedtch.c
+++ b/drivers/usb/atm/speedtch.c
@@ -357,15 +357,15 @@ static int speedtch_find_firmware(struct usbatm_data *usbatm, struct usb_interfa
 	sprintf(buf, "speedtch-%d.bin.%x.%02x", phase, major_revision, minor_revision);
 	usb_dbg(usbatm, "%s: looking for %s\n", __func__, buf);
 
-	if (request_firmware(fw_p, buf, dev)) {
+	if (request_firmware_direct(fw_p, buf, dev)) {
 		sprintf(buf, "speedtch-%d.bin.%x", phase, major_revision);
 		usb_dbg(usbatm, "%s: looking for %s\n", __func__, buf);
 
-		if (request_firmware(fw_p, buf, dev)) {
+		if (request_firmware_direct(fw_p, buf, dev)) {
 			sprintf(buf, "speedtch-%d.bin", phase);
 			usb_dbg(usbatm, "%s: looking for %s\n", __func__, buf);
 
-			if (request_firmware(fw_p, buf, dev)) {
+			if (request_firmware_direct(fw_p, buf, dev)) {
 				usb_err(usbatm, "%s: no stage %d firmware found!\n", __func__, phase);
 				return -ENOENT;
 			}
-- 
2.55.0