[PATCH v2 1/3] wifi: carl9170: bound memcpy length in cmd callback to prevent OOB read

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

When the firmware sends a command response with a length mismatch,
carl9170_cmd_callback() logs the mismatch and calls carl9170_restart()
but then falls through to memcpy(ar->readbuf, buffer + 4, len - 4).
Since len comes from the firmware and can exceed ar->readlen, this
copies more data than the readbuf was allocated for.

Bound the memcpy to min(len - 4, ar->readlen) so that the response
is still completed -- avoiding repeated restarts from queued garbage --
while preventing an overread past the response buffer.

Fixes: a84fab3cbfdc ("carl9170: 802.11 rx/tx processing and usb backend")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Changes in v2:
  - v2: bound memcpy with min_t() instead of adding early return after
    carl9170_restart(), per Christian Lamparter's feedback. The restart
    path must handle queued responses gracefully.

drivers/net/wireless/ath/carl9170/rx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/carl9170/rx.c b/drivers/net/wireless/ath/carl9170/rx.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/net/wireless/ath/carl9170/rx.c
+++ b/drivers/net/wireless/ath/carl9170/rx.c
@@ -151,7 +151,8 @@ static void carl9170_cmd_callback(struct ar9170 *ar, u32 len, void *buffer)
 	spin_lock(&ar->cmd_lock);
 	if (ar->readbuf) {
 		if (len >= 4)
-			memcpy(ar->readbuf, buffer + 4, len - 4);
+			memcpy(ar->readbuf, buffer + 4,
+			       min_t(u32, len - 4, ar->readlen));

 		ar->readbuf = NULL;
 	}
--
2.43.0