linux-kernel - [PATCH] wifi: mac80211: Write cnt before copying in ieee80211_copy_rnr

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Message-Id: <20250721182521.work.540-kees@kernel.org>
Date: Mon, 21 Jul 2025 11:25:22 -0700
From: Kees Cook <kees@...nel.org>
To: Johannes Berg <johannes@...solutions.net>
Cc: Kees Cook <kees@...nel.org>,
	linux-wireless@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Jeff Johnson <jeff.johnson@....qualcomm.com>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] wifi: mac80211: Write cnt before copying in ieee80211_copy_rnr_beacon()

While I caught the need for setting cnt early in nl80211_parse_rnr_elems()
in the original annotation of struct cfg80211_rnr_elems with __counted_by,
I missed a similar pattern in ieee80211_copy_rnr_beacon(). Fix this by
moving the cnt assignment to before the loop.

Fixes: 7b6d7087031b ("wifi: cfg80211: Annotate struct cfg80211_rnr_elems with __counted_by")
Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: Johannes Berg <johannes@...solutions.net>
Cc: <linux-wireless@...r.kernel.org>
---
 net/mac80211/cfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 4f20d57ab913..2ed07fa121ab 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1176,13 +1176,13 @@ ieee80211_copy_rnr_beacon(u8 *pos, struct cfg80211_rnr_elems *dst,
 {
 	int i, offset = 0;
 
+	dst->cnt = src->cnt;
 	for (i = 0; i < src->cnt; i++) {
 		memcpy(pos + offset, src->elem[i].data, src->elem[i].len);
 		dst->elem[i].len = src->elem[i].len;
 		dst->elem[i].data = pos + offset;
 		offset += dst->elem[i].len;
 	}
-	dst->cnt = src->cnt;
 
 	return offset;
 }
-- 
2.34.1