[PATCH] brcmfmac: fix possible buffer overflow in brcmf_cfg80211_mgmt_tx()

* [PATCH] brcmfmac: fix possible buffer overflow in brcmf_cfg80211_mgmt_tx()
@ 2017-07-07 12:01 Arend van Spriel
  2017-07-07 12:47 ` Sedat Dilek
  2017-07-07 13:17 ` Johannes Berg
  0 siblings, 2 replies; 6+ messages in thread
From: Arend van Spriel @ 2017-07-07 12:01 UTC (permalink / raw)
  To: Kalle Valo; +Cc: Linus Torvalds, linux-wireless, Arend van Spriel

The lower level nl80211 code in cfg80211 ensures that "len" is between
25 and NL80211_ATTR_FRAME (2304).  We subtract DOT11_MGMT_HDR_LEN (24) from
"len" so thats's max of 2280.  However, the action_frame->data[] buffer is
only BRCMF_FIL_ACTION_FRAME_SIZE (1800) bytes long so this memcpy() can
overflow.

	memcpy(action_frame->data, &buf[DOT11_MGMT_HDR_LEN],
	       le16_to_cpu(action_frame->len));

Reported-by: "freenerguo(郭大兴)" <freenerguo@tencent.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
---
Hi Kalle,

Here is the patch as Linus send it to us and security@kernel.org. I
removed the lower bound check as that is already done in cfg80211.
Now I signed off on the patch although formally I suppose Linus should
sign it off. Putting it out there so people can respond as deemed
necessary.

Now fingers crossed whether patchwork will properly deal with the UTF-8
characters :-p

Regards,
Arend
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
index cd1d673..d182a00 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
@@ -4851,6 +4851,11 @@ static int brcmf_cfg80211_stop_ap(struct wiphy *wiphy, struct net_device *ndev)
 		cfg80211_mgmt_tx_status(wdev, *cookie, buf, len, true,
 					GFP_KERNEL);
 	} else if (ieee80211_is_action(mgmt->frame_control)) {
+		if (len > BRCMF_FIL_ACTION_FRAME_SIZE + DOT11_MGMT_HDR_LEN) {
+			brcmf_err("invalid action frame length\n");
+			err = -EINVAL;
+			goto exit;
+		}
 		af_params = kzalloc(sizeof(*af_params), GFP_KERNEL);
 		if (af_params == NULL) {
 			brcmf_err("unable to allocate frame\n");
-- 
1.9.1

^ permalink raw reply related	[flat|nested] 6+ messages in thread