Subject: [PATCH 2/3] ath6kl: fix division by zero in send path

From: Johan Hovold <[email-masked]>
Date: Tue, 26 Oct 2021 11:52:13 +0200

Add the missing endpoint max-packet sanity check to probe() to avoid
division by zero in ath10k_usb_hif_tx_sg() in case a malicious device
has broken descriptors (or when doing descriptor fuzz testing).

Note that USB core will reject URBs submitted for endpoints with zero
wMaxPacketSize but that drivers doing packet-size calculations still
need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
endpoint descriptors with maxpacket=0")).

Fixes: 9cbee358687e ("ath6kl: add full USB support")
Cc: [email-masked]      # 3.5
Signed-off-by: Johan Hovold <[email-masked]>
---
 drivers/net/wireless/ath/ath6kl/usb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
index bd367b79a4d3..aba70f35e574 100644
--- a/drivers/net/wireless/ath/ath6kl/usb.c
+++ b/drivers/net/wireless/ath/ath6kl/usb.c
@@ -340,6 +340,11 @@ static int ath6kl_usb_setup_pipe_resources(struct ath6kl_usb *ar_usb)
 				   le16_to_cpu(endpoint->wMaxPacketSize),
 				   endpoint->bInterval);
 		}
+
+		/* Ignore broken descriptors. */
+		if (usb_endpoint_maxp(endpoint) == 0)
+			continue;
+
 		urbcount = 0;
 
 		pipe_num =
-- 
2.32.0