From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Christian Eggers <ceggers@arri.de>,
	Luiz Augusto von Dentz <luiz.von.dentz@intel.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12 380/460] Bluetooth: LE L2CAP: Disconnect if received packets SDU exceeds IMTU
Date: Mon, 23 Mar 2026 14:46:16 +0100
Message-ID: <20260323134535.908169454@linuxfoundation.org>
In-Reply-To: <20260323134526.647552166@linuxfoundation.org>
References: <20260323134526.647552166@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christian Eggers <ceggers@arri.de>

[ Upstream commit e1d9a66889867c232657a9b6f25d451d7c3ab96f ]

Core 6.0, Vol 3, Part A, 3.4.3:
"If the SDU length field value exceeds the receiver's MTU, the receiver
shall disconnect the channel..."

This fixes L2CAP/LE/CFC/BV-26-C (running together with 'l2test -r -P
0x0027 -V le_public -I 100').

Fixes: aac23bf63659 ("Bluetooth: Implement LE L2CAP reassembly")
Signed-off-by: Christian Eggers <ceggers@arri.de>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/bluetooth/l2cap_core.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index a95949bc36b2a..de8e18fe50557 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -6619,8 +6619,10 @@ static int l2cap_ecred_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb)
 		return -ENOBUFS;
 	}
 
-	if (chan->imtu < skb->len) {
-		BT_ERR("Too big LE L2CAP PDU");
+	if (skb->len > chan->imtu) {
+		BT_ERR("Too big LE L2CAP PDU: len %u > %u", skb->len,
+		       chan->imtu);
+		l2cap_send_disconn_req(chan, ECONNRESET);
 		return -ENOBUFS;
 	}
 
@@ -6646,7 +6648,9 @@ static int l2cap_ecred_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb)
 		       sdu_len, skb->len, chan->imtu);
 
 		if (sdu_len > chan->imtu) {
-			BT_ERR("Too big LE L2CAP SDU length received");
+			BT_ERR("Too big LE L2CAP SDU length: len %u > %u",
+			       skb->len, sdu_len);
+			l2cap_send_disconn_req(chan, ECONNRESET);
 			err = -EMSGSIZE;
 			goto failed;
 		}
-- 
2.51.0