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From: Kees Cook <keescook@chromium.org>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Kees Cook <keescook@chromium.org>,
	Nathan Chancellor <nathan@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,
	linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org,
	Jeff Johnson <quic_jjohnson@quicinc.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: [PATCH] wifi: nl80211: Avoid address calculations via out of bounds array indexing
Date: Wed, 24 Apr 2024 15:01:01 -0700
Message-Id: <20240424220057.work.819-kees@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Before request->channels[] can be used, request->n_channels must be set.
Additionally, address calculations for memory after the "channels" array
need to be calculated from the allocation base ("request") rather than
via the first "out of bounds" index of "channels", otherwise run-time
bounds checking will throw a warning.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Fixes: e3eac9f32ec0 ("wifi: cfg80211: Annotate struct cfg80211_scan_request with __counted_by")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
---
 net/wireless/nl80211.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index f391b4055944..f1ed0981147e 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -9163,6 +9163,7 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 	struct wiphy *wiphy;
 	int err, tmp, n_ssids = 0, n_channels, i;
 	size_t ie_len, size;
+	size_t ssids_offset, ie_offset;
 
 	wiphy = &rdev->wiphy;
 
@@ -9208,21 +9209,20 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 		return -EINVAL;
 
 	size = struct_size(request, channels, n_channels);
+	ssids_offset = size;
 	size = size_add(size, array_size(sizeof(*request->ssids), n_ssids));
+	ie_offset = size;
 	size = size_add(size, ie_len);
 	request = kzalloc(size, GFP_KERNEL);
 	if (!request)
 		return -ENOMEM;
+	request->n_channels = n_channels;
 
 	if (n_ssids)
-		request->ssids = (void *)&request->channels[n_channels];
+		request->ssids = (void *)request + ssids_offset;
 	request->n_ssids = n_ssids;
-	if (ie_len) {
-		if (n_ssids)
-			request->ie = (void *)(request->ssids + n_ssids);
-		else
-			request->ie = (void *)(request->channels + n_channels);
-	}
+	if (ie_len)
+		request->ie = (void *)request + ie_offset;
 
 	i = 0;
 	if (scan_freqs) {
-- 
2.34.1