FAILED: patch "[PATCH] Bluetooth: L2CAP: Fix accepting multiple L2CAP_ECRED_CONN_REQ" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 5b3e2052334f2ff6d5200e952f4aa66994d09899
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026032112-attain-reprocess-ab80@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5b3e2052334f2ff6d5200e952f4aa66994d09899 Mon Sep 17 00:00:00 2001
From: Luiz Augusto von Dentz <[email protected]>
Date: Tue, 3 Mar 2026 13:29:53 -0500
Subject: [PATCH] Bluetooth: L2CAP: Fix accepting multiple L2CAP_ECRED_CONN_REQ

Currently the code attempts to accept requests regardless of the command identifier which may cause multiple requests to be marked as pending (FLAG_DEFER_SETUP) which can cause more than L2CAP_ECRED_MAX_CID(5) to be allocated in l2cap_ecred_rsp_defer causing an overflow.

The spec is quite clear that the same identifier shall not be used on subsequent requests:

'Within each signaling channel a different Identifier shall be used for each successive request or indication.'
https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/host/logical-link-control-and-adaptation-protocol-specification.html#UUID-32a25a06-4aa4-c6c7-77c5-dcfe3682355d

So this attempts to check if there are any channels pending with the same identifier and rejects if any are found.

index 780136e18aae..9d5b8d4d375a 100644
@@ -5055,7 +5055,7 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 	u16 mtu, mps;
 	__le16 psm;
 	u8 result, rsp_len = 0;
-	int i, num_scid;
+	int i, num_scid = 0;
 	bool defer = false;
 
 	if (!enable_ecred)

@@ -5068,6 +5068,14 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 		goto response;
 	}
 
+	/* Check if there are no pending channels with the same ident */
+	__l2cap_chan_list_id(conn, cmd->ident, l2cap_ecred_list_defer,
+			     &num_scid);
+	if (num_scid) {
+		result = L2CAP_CR_LE_INVALID_PARAMS;
+		goto response;
+	}
+
 	cmd_len -= sizeof(*req);
 	num_scid = cmd_len / sizeof(u16);
 

From: Luiz Augusto von Dentz <[email protected]>

[ Upstream commit 5b3e2052334f2ff6d5200e952f4aa66994d09899 ]

Currently the code attempts to accept requests regardless of the command identifier which may cause multiple requests to be marked as pending (FLAG_DEFER_SETUP) which can cause more than L2CAP_ECRED_MAX_CID(5) to be allocated in l2cap_ecred_rsp_defer causing an overflow.

The spec is quite clear that the same identifier shall not be used on subsequent requests:

'Within each signaling channel a different Identifier shall be used for each successive request or indication.'
https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/host/logical-link-control-and-adaptation-protocol-specification.html#UUID-32a25a06-4aa4-c6c7-77c5-dcfe3682355d

So this attempts to check if there are any channels pending with the same identifier and rejects if any are found.

---
 net/bluetooth/l2cap_core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

index 88f8c98afd5f5..d9ac64bc5407e 100644
@@ -6036,7 +6036,7 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 	u16 mtu, mps;
 	__le16 psm;
 	u8 result, len = 0;
-	int i, num_scid;
+	int i, num_scid = 0;
 	bool defer = false;
 
 	if (!enable_ecred)

@@ -6047,6 +6047,14 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 		goto response;
 	}
 
+	/* Check if there are no pending channels with the same ident */
+	__l2cap_chan_list_id(conn, cmd->ident, l2cap_ecred_list_defer,
+			     &num_scid);
+	if (num_scid) {
+		result = L2CAP_CR_LE_INVALID_PARAMS;
+		goto response;
+	}
+
 	cmd_len -= sizeof(*req);
 	num_scid = cmd_len / sizeof(u16);
 

2.51.0