[PATCH v2] wifi: brcmfmac: cyw: fix heap overflow on a short auth frame

brcmf_notify_auth_frame_rx() takes the frame length from the firmware
event and copies the frame body with the management header offset
subtracted:

	u32 mgmt_frame_len = e->datalen - sizeof(struct brcmf_rx_mgmt_data);
	...
	memcpy(&mgmt_frame->u, frame,
	       mgmt_frame_len - offsetof(struct ieee80211_mgmt, u));

The only length check is e->datalen >= sizeof(*rxframe), so mgmt_frame_len
can be anything from 0 up. offsetof(struct ieee80211_mgmt, u) is 24. When
mgmt_frame_len is below that, the subtraction wraps as an unsigned value to
a huge length. The memcpy then runs far past the kzalloc'd buffer. A
malicious or malfunctioning AP can make the frame short during the
external SAE auth exchange, so this is a remotely triggered heap overflow.

Reject frames shorter than the management header offset before the copy.

Fixes: 66f909308a7c ("wifi: brcmfmac: cyw: support external SAE authentication in station mode")
Cc: [email protected]
Co-developed-by: Kaixuan Li <[email protected]>
Signed-off-by: Kaixuan Li <[email protected]>
Signed-off-by: Maoyi Xie <[email protected]>
Acked-by: Arend van Spriel <[email protected]>
---
v2: drop the Link: tag (Arend), add Arend's Acked-by.

v1: https://lore.kernel.org/r/[email protected]
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/core.c
index ce09d44fa7..873754be51 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/core.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/core.c
@@ -293,6 +293,12 @@ brcmf_notify_auth_frame_rx(struct brcmf_if *ifp,
 		return -EINVAL;
 	}
 
+	if (mgmt_frame_len < offsetof(struct ieee80211_mgmt, u)) {
+		bphy_err(drvr, "Event %s (%d) frame too small. Ignore\n",
+			 brcmf_fweh_event_name(e->event_code), e->event_code);
+		return -EINVAL;
+	}
+
 	wdev = &ifp->vif->wdev;
 	WARN_ON(!wdev);
 
-- 
2.34.1