[PATCH v2] wifi: ath9k: don't allow to overwrite ENDPOINT0 attributes

[Fedor Pchelkin]

A bad USB device is able to construct a service connection response
message with target endpoint being ENDPOINT0 which is reserved for
HTC_CTRL_RSVD_SVC and should not be modified to be used for any other
services.

Reject such service connection responses.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
Reported-by: syzbot+b68fbebe56d8362907e8@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>
---
v2: per Toke's remark, use ENDPOINT0 macro and give a comment explaining
why it should be checked.

 drivers/net/wireless/ath/ath9k/htc_hst.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath9k/htc_hst.c b/drivers/net/wireless/ath/ath9k/htc_hst.c
index fe62ff668f75..99667aba289d 100644
--- a/drivers/net/wireless/ath/ath9k/htc_hst.c
+++ b/drivers/net/wireless/ath/ath9k/htc_hst.c
@@ -114,7 +114,13 @@ static void htc_process_conn_rsp(struct htc_target *target,
 
 	if (svc_rspmsg->status == HTC_SERVICE_SUCCESS) {
 		epid = svc_rspmsg->endpoint_id;
-		if (epid < 0 || epid >= ENDPOINT_MAX)
+
+		/* Check that the received epid for the endpoint to attach
+		 * a new service is valid. ENDPOINT0 can't be used here as it
+		 * is already reserved for HTC_CTRL_RSVD_SVC service and thus
+		 * should not be modified.
+		 */
+		if (epid <= ENDPOINT0 || epid >= ENDPOINT_MAX)
 			return;
 
 		service_id = be16_to_cpu(svc_rspmsg->service_id);
-- 
2.34.1