linux-kernel - [PATCH] net: mac80211: cfg: Initialize cnt before accessing elem in ieee80211_copy_mbssid

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Message-Id: <20241123172500.311853-1-lihaoyu499@gmail.com>
Date: Sun, 24 Nov 2024 01:25:00 +0800
From: Haoyu Li <lihaoyu499@...il.com>
To: Johannes Berg <johannes@...solutions.net>
Cc: Kees Cook <kees@...nel.org>,
	"Gustavo A . R . Silva" <gustavoars@...nel.org>,
	linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Haoyu Li <lihaoyu499@...il.com>
Subject: [PATCH] net: mac80211: cfg: Initialize cnt before accessing elem in ieee80211_copy_mbssid_beacon

With the new __counted_by annocation in cfg80211_mbssid_elems,
the "cnt" struct member must be set before accessing the "elem"
array. Failing to do so will trigger a runtime warning when enabling
CONFIG_UBSAN_BOUNDS and CONFIG_FORTIFY_SOURCE.

Fixes: c14679d7005a ("wifi: cfg80211: Annotate struct cfg80211_mbssid_elems with __counted_by")
Signed-off-by: Haoyu Li <lihaoyu499@...il.com>
---
 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 61a824ec33da..1dd61c9bb8f1 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1088,13 +1088,13 @@ ieee80211_copy_mbssid_beacon(u8 *pos, struct cfg80211_mbssid_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