[PATCH 2/2] wifi: libertas: don't kill URBs in interrupt context

[Heitor Alves de Siqueira]

Serialization for the TX path was enforced by calling
usb_kill_urb()/usb_kill_anchored_urbs(), to prevent transmission before
a previous URB was completed. usb_tx_block() can be called from
interrupt context (e.g. in the HCD giveback path), so we can't always
use it to kill in-flight URBs.

Prevent sleeping during interrupt context by checking the tx_submitted
anchor for existing URBs. We now return -EBUSY, to indicate there's
a pending request.

Reported-by: syzbot+74afbb6355826ffc2239@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=74afbb6355826ffc2239
Fixes: d66676e6ca96 ("wifi: libertas: fix WARNING in usb_tx_block")
Signed-off-by: Heitor Alves de Siqueira <halves@xxxxxxxxxx>
---
 drivers/net/wireless/marvell/libertas/if_usb.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/marvell/libertas/if_usb.c b/drivers/net/wireless/marvell/libertas/if_usb.c
index 11cd1422f46a..d3b9f7619a1a 100644
--- a/drivers/net/wireless/marvell/libertas/if_usb.c
+++ b/drivers/net/wireless/marvell/libertas/if_usb.c
@@ -429,7 +429,12 @@ static int usb_tx_block(struct if_usb_card *cardp, uint8_t *payload, uint16_t nb
 		goto tx_ret;
 	}
 
-	usb_kill_anchored_urbs(&cardp->tx_submitted);
+	/* check if there are pending URBs */
+	if (!usb_anchor_empty(&cardp->tx_submitted)) {
+		lbs_deb_usbd(&cardp->udev->dev, "%s failed: pending URB\n", __func__);
+		ret = -EBUSY;
+		goto tx_ret;
+	}
 
 	usb_fill_bulk_urb(cardp->tx_urb, cardp->udev,
 			  usb_sndbulkpipe(cardp->udev,

-- 
2.53.0