[PATCH v2 2/2] usb: cdns3: fix memory double free when handle zero packet

[Frank Li]

829  if (request->complete) {
830          spin_unlock(&priv_dev->lock);
831          usb_gadget_giveback_request(&priv_ep->endpoint,
832                                    request);
833          spin_lock(&priv_dev->lock);
834  }
835
836  if (request->buf == priv_dev->zlp_buf)
837      cdns3_gadget_ep_free_request(&priv_ep->endpoint, request);

Driver append an additional zero packet request when queue a packet, which
length mod max packet size is 0. When transfer complete, run to line 831,
usb_gadget_giveback_request() will free this requestion. 836 condition is
true, so cdns3_gadget_ep_free_request() free this request again.

Log:

[ 1920.140696][  T150] BUG: KFENCE: use-after-free read in cdns3_gadget_giveback+0x134/0x2c0 [cdns3]
[ 1920.140696][  T150]
[ 1920.151837][  T150] Use-after-free read at 0x000000003d1cd10b (in kfence-#36):
[ 1920.159082][  T150]  cdns3_gadget_giveback+0x134/0x2c0 [cdns3]
[ 1920.164988][  T150]  cdns3_transfer_completed+0x438/0x5f8 [cdns3]

Add check at line 829, skip call usb_gadget_giveback_request() if it is
additional zero length packet request. Needn't call
usb_gadget_giveback_request() because it is allocated in this driver.

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
---
 drivers/usb/cdns3/cdns3-gadget.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
index d6723d31fc6e2..fd1beb10bba72 100644
--- a/drivers/usb/cdns3/cdns3-gadget.c
+++ b/drivers/usb/cdns3/cdns3-gadget.c
@@ -828,7 +828,11 @@ void cdns3_gadget_giveback(struct cdns3_endpoint *priv_ep,
 			return;
 	}
 
-	if (request->complete) {
+	/*
+	 * zlp request is appended by driver, needn't call usb_gadget_giveback_request() to notify
+	 * gadget composite driver.
+	 */
+	if (request->complete && request->buf != priv_dev->zlp_buf) {
 		spin_unlock(&priv_dev->lock);
 		usb_gadget_giveback_request(&priv_ep->endpoint,
 					    request);
-- 
2.34.1