[PATCH V2] brcmfmac: fix possible buffer overflow in brcmf_cfg80211_mgmt_tx()

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));

Cc: stable@vger.kernel.org # 3.9.x
Fixes: 18e2f61db3b70 ("brcmfmac: P2P action frame tx.")
Reported-by: "freenerguo(郭大兴)" <redacted>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
---
 V2:
  - added Fixes: tag and Cc: for stable kernels.
  - Cc: patch to netdev list.
---
Hi David,

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.

The reason for submitting it to your tree is the fact that Kalle is
on vacation for next 10 days or so which was indicated to me by Johannes.
The patch applies to the master branch of your net repository. For
reference V1 of this patch can be found here [1].

Regards,
Arend

[1] https://patchwork.kernel.org/patch/9829977/
---
 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

On Fri, Jul 7, 2017 at 1:09 PM, Arend van Spriel
[off-list ref] wrote:

Now I signed off on the patch although formally I suppose Linus should
sign it off.

You can certainly consider it

   Signed-off-by: Linus Torvalds [off-list ref]

but I really don't need the authorship (or resulting sign-off
requirement) because multiple people ended up sending in very similar
patches.

All the real work was in actually finding the issue.

                  Linus