From: Seungjin Bae In ar5523_data_rx_cb(), the `rxlen` variable is derived from desc->len, which is provided by the USB device. The function checks for an upper bound (rxlen > ar->rxbufsz) and for a zero value (!rxlen), but it fails to check for a proper lower bound against the size of the descriptor. If a malicious device provides an `rxlen` value that is positive but smaller than sizeof(struct ar5523_rx_desc), the subtraction in the call to skb_put() will result in an integer underflow. This passes a very large unsigned value to skb_put(), which then triggers a kernel panic upon detecting the potential buffer overflow. Fix this by adding a check to ensure `rxlen` is at least sizeof(struct ar5523_rx_desc) before performing the subtraction. Additionally, `rxlen` is not cross-checked against usblen (the number of bytes actually received). Since the frame layout is [ar5523_chunk][802.11 payload][ar5523_rx_desc] and `usblen` covers the whole buffer, a valid rxlen cannot exceed `usblen - sizeof(chunk)`. A device reporting a larger `rxlen` would cause skb_put() to expose descriptor trailer bytes or uninitialized skb tail data as 802.11 payload to ieee80211_rx_irqsafe(). Add a check to reject such frames. Fixes: b7d572e1871df ("ar5523: Add new driver") Suggested-by: Jeff Johnson Signed-off-by: Seungjin Bae --- v1 -> v2: cross-check rxlen against usblen to prevent overreading past the received payload drivers/net/wireless/ath/ar5523/ar5523.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/net/wireless/ath/ar5523/ar5523.c b/drivers/net/wireless/ath/ar5523/ar5523.c index 66ac396858a5..3ee4b020f416 100644 --- a/drivers/net/wireless/ath/ar5523/ar5523.c +++ b/drivers/net/wireless/ath/ar5523/ar5523.c @@ -589,6 +589,18 @@ static void ar5523_data_rx_cb(struct urb *urb) goto skip; } + if (rxlen < sizeof(struct ar5523_rx_desc)) { + ar5523_dbg(ar, "RX: Bad descriptor (len=%u is too small)\n", + rxlen); + goto skip; + } + + if (rxlen > usblen - sizeof(struct ar5523_chunk)) { + ar5523_dbg(ar, "RX: rxlen too large (rxlen=%u usblen=%d)\n", + rxlen, usblen); + goto skip; + } + skb_reserve(data->skb, sizeof(*chunk)); skb_put(data->skb, rxlen - sizeof(struct ar5523_rx_desc)); -- 2.43.0