[PATCH v2] staging: rtl8723bs: validate monitor transmit frame lengths

[Mariano Baragiola <mbaragiola@linux.com>]

rtw_cfg80211_monitor_if_xmit_entry() removes the radiotap header and
then reads the 802.11 frame control field without checking that a base
802.11 header remains.

The data path also pulls the calculated 802.11, QoS and SNAP header
span before confirming that the skb contains it. A truncated frame can
therefore cause out-of-bounds reads or leave insufficient data for the
Ethernet address writes.

Reject frames that do not contain the base 802.11 header and data
frames that do not contain their complete calculated header span.

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Mariano Baragiola <mbaragiola@linux.com>
---
 drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
index 6a97afd89dc7..bed8192ab44f 100644
--- a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
+++ b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
@@ -2033,6 +2033,8 @@ static netdev_tx_t rtw_cfg80211_monitor_if_xmit_entry(struct sk_buff *skb, struc
 
 	/* Skip the ratio tap header */
 	skb_pull(skb, rtap_len);
+	if (unlikely(skb->len < dot11_hdr_len))
+		goto fail;
 
 	dot11_hdr = (struct ieee80211_hdr *)skb->data;
 	frame_control = le16_to_cpu(dot11_hdr->frame_control);
@@ -2045,6 +2047,8 @@ static netdev_tx_t rtw_cfg80211_monitor_if_xmit_entry(struct sk_buff *skb, struc
 			qos_len = 2;
 		if ((frame_control & 0x0300) == 0x0300)
 			dot11_hdr_len += 6;
+		if (unlikely(skb->len < dot11_hdr_len + qos_len + snap_len))
+			goto fail;
 
 		memcpy(dst_mac_addr, dot11_hdr->addr1, sizeof(dst_mac_addr));
 		memcpy(src_mac_addr, dot11_hdr->addr2, sizeof(src_mac_addr));
-- 
2.55.0