[PATCH 1/3] wifi: ath9k: avoid referencing uninit memory in ath9k_wmi_ctrl_rx

[Fedor Pchelkin <pchelkin@ispras.ru>]

For the reasons described in commit b383e8abed41 ("wifi: ath9k: avoid
uninit memory read in ath9k_htc_rx_msg()"), ath9k_htc_rx_msg() should
validate pkt_len before accessing the SKB. For example, the obtained SKB
may have uninitialized memory in the case of
ioctl(USB_RAW_IOCTL_EP_WRITE).

Implement sanity checking inside the corresponding endpoint RX handlers:
ath9k_wmi_ctrl_rx() and ath9k_htc_rxep(). Otherwise, uninit memory can
be referenced.

Add comments briefly describing the issue.

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

Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
Reported-and-tested-by: syzbot+f2cb6e0ffdb961921e4d@syzkaller.appspotmail.com
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
---
 drivers/net/wireless/ath/ath9k/htc_drv_txrx.c | 6 ++++++
 drivers/net/wireless/ath/ath9k/htc_hst.c      | 4 ++++
 drivers/net/wireless/ath/ath9k/wmi.c          | 8 ++++++++
 3 files changed, 18 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
index 672789e3c55d..957efb26019d 100644
--- a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
+++ b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
@@ -1147,6 +1147,12 @@ void ath9k_htc_rxep(void *drv_priv, struct sk_buff *skb,
 	if (!data_race(priv->rx.initialized))
 		goto err;
 
+	/* Validate the obtained SKB so that it is handled without error
+	 * inside rx_tasklet handler.
+	 */
+	if (unlikely(skb->len < sizeof(struct ieee80211_hdr)))
+		goto err;
+
 	spin_lock_irqsave(&priv->rx.rxbuflock, flags);
 	list_for_each_entry(tmp_buf, &priv->rx.rxbuf, list) {
 		if (!tmp_buf->in_process) {
diff --git a/drivers/net/wireless/ath/ath9k/htc_hst.c b/drivers/net/wireless/ath/ath9k/htc_hst.c
index fe62ff668f75..9d0d9d0e1aa8 100644
--- a/drivers/net/wireless/ath/ath9k/htc_hst.c
+++ b/drivers/net/wireless/ath/ath9k/htc_hst.c
@@ -475,6 +475,10 @@ void ath9k_htc_rx_msg(struct htc_target *htc_handle,
 		skb_pull(skb, sizeof(struct htc_frame_hdr));
 
 		endpoint = &htc_handle->endpoint[epid];
+
+		/* The endpoint RX handlers should implement their own
+		 * additional SKB sanity checking
+		 */
 		if (endpoint->ep_callbacks.rx)
 			endpoint->ep_callbacks.rx(endpoint->ep_callbacks.priv,
 						  skb, epid);
diff --git a/drivers/net/wireless/ath/ath9k/wmi.c b/drivers/net/wireless/ath/ath9k/wmi.c
index 19345b8f7bfd..2e7c361b62f5 100644
--- a/drivers/net/wireless/ath/ath9k/wmi.c
+++ b/drivers/net/wireless/ath/ath9k/wmi.c
@@ -204,6 +204,10 @@ static void ath9k_wmi_rsp_callback(struct wmi *wmi, struct sk_buff *skb)
 {
 	skb_pull(skb, sizeof(struct wmi_cmd_hdr));
 
+	/* Once again validate the SKB. */
+	if (unlikely(skb->len < wmi->cmd_rsp_len))
+		return;
+
 	if (wmi->cmd_rsp_buf != NULL && wmi->cmd_rsp_len != 0)
 		memcpy(wmi->cmd_rsp_buf, skb->data, wmi->cmd_rsp_len);
 
@@ -221,6 +225,10 @@ static void ath9k_wmi_ctrl_rx(void *priv, struct sk_buff *skb,
 	if (unlikely(wmi->stopped))
 		goto free_skb;
 
+	/* Validate the obtained SKB. */
+	if (unlikely(skb->len < sizeof(struct wmi_cmd_hdr)))
+		goto free_skb;
+
 	hdr = (struct wmi_cmd_hdr *) skb->data;
 	cmd_id = be16_to_cpu(hdr->command_id);
 
-- 
2.34.1