netdev - [PATCH] wifi: ath: Silence memcpy run-time false positive warning

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Message-Id: <20230210054310.never.554-kees@kernel.org>
Date:   Thu,  9 Feb 2023 21:43:13 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Kalle Valo <kvalo@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] wifi: ath: Silence memcpy run-time false positive warning

The memcpy() in ath_key_config() was attempting to write across
neighboring struct members in struct ath_keyval. Introduce a wrapping
struct_group, kv_values, to be the addressable target of the memcpy
without overflowing an individual member. Silences the false positive
run-time warning:

  memcpy: detected field-spanning write (size 32) of single field "hk.kv_val" at drivers/net/wireless/ath/key.c:506 (size 16)

Link: https://bbs.archlinux.org/viewtopic.php?id=282254
Cc: Kalle Valo <kvalo@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: linux-wireless@...r.kernel.org
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/net/wireless/ath/ath.h | 12 +++++++-----
 drivers/net/wireless/ath/key.c |  2 +-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/ath/ath.h b/drivers/net/wireless/ath/ath.h
index f083fb9038c3..f02a308a9ffc 100644
--- a/drivers/net/wireless/ath/ath.h
+++ b/drivers/net/wireless/ath/ath.h
@@ -96,11 +96,13 @@ struct ath_keyval {
 	u8 kv_type;
 	u8 kv_pad;
 	u16 kv_len;
-	u8 kv_val[16]; /* TK */
-	u8 kv_mic[8]; /* Michael MIC key */
-	u8 kv_txmic[8]; /* Michael MIC TX key (used only if the hardware
-			 * supports both MIC keys in the same key cache entry;
-			 * in that case, kv_mic is the RX key) */
+	struct_group(kv_values,
+		u8 kv_val[16]; /* TK */
+		u8 kv_mic[8]; /* Michael MIC key */
+		u8 kv_txmic[8]; /* Michael MIC TX key (used only if the hardware
+				 * supports both MIC keys in the same key cache entry;
+				 * in that case, kv_mic is the RX key) */
+	);
 };
 
 enum ath_cipher {
diff --git a/drivers/net/wireless/ath/key.c b/drivers/net/wireless/ath/key.c
index 61b59a804e30..b7b61d4f02ba 100644
--- a/drivers/net/wireless/ath/key.c
+++ b/drivers/net/wireless/ath/key.c
@@ -503,7 +503,7 @@ int ath_key_config(struct ath_common *common,
 
 	hk.kv_len = key->keylen;
 	if (key->keylen)
-		memcpy(hk.kv_val, key->key, key->keylen);
+		memcpy(&hk.kv_values, key->key, key->keylen);
 
 	if (!(key->flags & IEEE80211_KEY_FLAG_PAIRWISE)) {
 		switch (vif->type) {
-- 
2.34.1