FAILED: patch "[PATCH] Bluetooth: Add more enc key size check" 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 04a342cc49a8522e99c9b3346371c329d841dcd2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023122845-moonscape-hermit-0bd5@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

04a342cc49a8 ("Bluetooth: Add more enc key size check")
278d933e12f1 ("Bluetooth: Normalize HCI_OP_READ_ENC_KEY_SIZE cmdcmplt") c8992cffbe74 ("Bluetooth: hci_event: Use of a function table to handle Command Complete") 3e54c5890c87 ("Bluetooth: hci_event: Use of a function table to handle HCI events") 12cfe4176ad6 ("Bluetooth: HCI: Use skb_pull_data to parse LE Metaevents") 70a6b8de6af5 ("Bluetooth: HCI: Use skb_pull_data to parse Extended Inquiry Result event") 8d08d324fdcb ("Bluetooth: HCI: Use skb_pull_data to parse Inquiry Result with RSSI event") 27d9eb4bcac1 ("Bluetooth: HCI: Use skb_pull_data to parse Inquiry Result event") aadc3d2f42a5 ("Bluetooth: HCI: Use skb_pull_data to parse Number of Complete Packets event") e3f3a1aea871 ("Bluetooth: HCI: Use skb_pull_data to parse Command Complete event") ae61a10d9d46 ("Bluetooth: HCI: Use skb_pull_data to parse BR/EDR events") 3244845c6307 ("Bluetooth: hci_sync: Convert MGMT_OP_SSP")

thanks,

greg k-h

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

From 04a342cc49a8522e99c9b3346371c329d841dcd2 Mon Sep 17 00:00:00 2001
From: Alex Lu <[email protected]>
Date: Tue, 12 Dec 2023 10:30:34 +0800
Subject: [PATCH] Bluetooth: Add more enc key size check

When we are slave role and receives l2cap conn req when encryption has started, we should check the enc key size to avoid KNOB attack or BLUFFS attack.
From SIG recommendation, implementations are advised to reject service-level connections on an encrypted baseband link with key strengths below 7 octets.
A simple and clear way to achieve this is to place the enc key size check in hci_cc_read_enc_key_size()

The btmon log below shows the case that lacks enc key size check.

Address: BB:22:33:44:55:99 (OUI BB-22-33)
Class: 0x480104
Major class: Computer (desktop, notebook, PDA, organizers) Minor class: Desktop workstation
Capturing (Scanner, Microphone)
Telephony (Cordless telephony, Modem, Headset)
Link type: ACL (0x01)
< HCI Command: Accept Connection Request (0x01|0x0009) plen 7

        Address: BB:22:33:44:55:99 (OUI BB-22-33)
        Role: Peripheral (0x01)

      Accept Connection Request (0x01|0x0009) ncmd 2
        Status: Success (0x00)

        Status: Success (0x00)
        Handle: 1
        Address: BB:22:33:44:55:99 (OUI BB-22-33)
        Link type: ACL (0x01)
        Encryption: Disabled (0x00)

...

        Status: Success (0x00)
        Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
        Encryption: Enabled with E0 (0x01)
< HCI Command: Read Encryption Key Size (0x05|0x0008) plen 2
        Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)

      Read Encryption Key Size (0x05|0x0008) ncmd 2
        Status: Success (0x00)
        Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
        Key size: 6

// We should check the enc key size
...

      L2CAP: Connection Request (0x02) ident 3 len 4
        PSM: 25 (0x0019)
        Source CID: 64
< ACL Data TX: Handle 1 flags 0x00 dlen 16
      L2CAP: Connection Response (0x03) ident 3 len 8
        Destination CID: 64
        Source CID: 64
        Result: Connection pending (0x0001)
        Status: Authorization pending (0x0002)

        Num handles: 1
        Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
        Count: 1
        #35: len 16 (25 Kb/s)
        Latency: 5 msec (2-7 msec ~4 msec)
< ACL Data TX: Handle 1 flags 0x00 dlen 16
      L2CAP: Connection Response (0x03) ident 3 len 8
        Destination CID: 64
        Source CID: 64
        Result: Connection successful (0x0000)
        Status: No further information available (0x0000)

index cc5fd290d529..ebf17b51072f 100644
@@ -750,9 +750,23 @@ static u8 hci_cc_read_enc_key_size(struct hci_dev *hdev, void *data,
 	} else {
 		conn->enc_key_size = rp->key_size;
 		status = 0;
+
+		if (conn->enc_key_size < hdev->min_enc_key_size) {
+			/* As slave role, the conn->state has been set to
+			 * BT_CONNECTED and l2cap conn req might not be received
+			 * yet, at this moment the l2cap layer almost does
+			 * nothing with the non-zero status.
+			 * So we also clear encrypt related bits, and then the
+			 * handler of l2cap conn req will get the right secure
+			 * state at a later time.
+			 */
+			status = HCI_ERROR_AUTH_FAILURE;
+			clear_bit(HCI_CONN_ENCRYPT, &conn->flags);
+			clear_bit(HCI_CONN_AES_CCM, &conn->flags);
+		}
 	}
 
-	hci_encrypt_cfm(conn, 0);
+	hci_encrypt_cfm(conn, status);
 
 done:
 	hci_dev_unlock(hdev);