[PATCH v2 2/2 6.1.y] Bluetooth: ISO: Copy BASE if service data matches EIR_BAA_SERVICE_UUID

[Jeremy Erazo (Devel Group)]

From: Jeremy Erazo <mendozayt13@xxxxxxxxx>

commit f4da3ee15de9944482382181329bb6d7335ca003 upstream.

Copy the content of a Periodic Advertisement Report to BASE only if
the service UUID is Basic Audio Announcement Service UUID.

[Stable backport rationale]

This fix landed in mainline v6.7 without a Fixes: tag, so the stable
autoselect bot never picked it up.  linux-6.1.y HEAD (v6.1.176) still
carries the pre-fix code at net/bluetooth/iso.c:1613:

	if (sk) {
		memcpy(iso_pi(sk)->base, ev3->data, ev3->length);
		iso_pi(sk)->base_len = ev3->length;
	}

ev3->length is __u8 and iso_pi(sk)->base is __u8[BASE_MAX_LENGTH] where
BASE_MAX_LENGTH is HCI_MAX_PER_AD_LENGTH(252) - EIR_SERVICE_DATA_LENGTH(4)
= 248.  When an attacker within BLE radio range sends an HCI_EV_LE_PER_ADV_REPORT
with ev3->length in [249, 255], the memcpy writes 1 to 7 bytes past the
buffer into the trailing fields of struct iso_pinfo, including the low
bytes of the iso_pi(sk)->conn pointer.  FORTIFY_SOURCE flags the write
with "memcpy: detected field-spanning write" but does not block it.

The upstream refactor addresses this by:
  1. Filtering via eir_get_service_data() so only the BASE portion of
     the PA payload is copied.
  2. Bounding the copy with base_len <= sizeof(iso_pi(sk)->base).

Backport notes for 6.1.y:
  * eir_get_service_data() is already declared in net/bluetooth/eir.h.
  * The header include for eir.h and the EIR_BAA_SERVICE_UUID define
    are added here, matching the upstream commit.
  * The put_user() addition in iso_sock_getsockopt() that was part of
    the same upstream commit is not included; that hunk is a separate
    getsockopt correctness fix and is not required for the OOB write
    fix (getsockopt(BT_ISO_BASE) is a controlled path that already
    validates optlen against sizeof(iso_pi(sk)->base)).  Applying the
    getsockopt hunk here would risk a user-visible ABI change on a
    stable branch.

Reachability: any host with an ISO listening socket bound as a
broadcast sink (LE Audio / Auracast).  No pairing required.

Fixes: 9c0826310bfb ("Bluetooth: ISO: Add support for periodic adv reports processing")
Cc: stable@xxxxxxxxxxxxxxx # 6.1.y
Signed-off-by: Claudia Draghicescu <claudia.rosu@xxxxxxx>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
[jerazo: backport to 6.1.y; add #include "eir.h" and EIR_BAA_SERVICE_UUID define; drop unrelated getsockopt hunk]
Signed-off-by: Jeremy Erazo <mendozayt13@xxxxxxxxx>
---
 net/bluetooth/iso.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index 7ea3e6335..6b8622bec 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -14,6 +14,8 @@
 #include <net/bluetooth/hci_core.h>
 #include <net/bluetooth/iso.h>
 
+#include "eir.h"
+
 static const struct proto_ops iso_sock_ops;
 
 static struct bt_sock_list iso_sk_list = {
@@ -46,6 +48,7 @@ static void iso_sock_kill(struct sock *sk);
 
 #define EIR_SERVICE_DATA_LENGTH 4
 #define BASE_MAX_LENGTH (HCI_MAX_PER_AD_LENGTH - EIR_SERVICE_DATA_LENGTH)
+#define EIR_BAA_SERVICE_UUID	0x1851
 
 struct iso_pinfo {
 	struct bt_sock		bt;
@@ -1606,12 +1609,16 @@ int iso_connect_ind(struct hci_dev *hdev, bdaddr_t *bdaddr, __u8 *flags)
 
 	ev3 = hci_recv_event_data(hdev, HCI_EV_LE_PER_ADV_REPORT);
 	if (ev3) {
+		size_t base_len = ev3->length;
+		u8 *base;
+
 		sk = iso_get_sock_listen(&hdev->bdaddr, bdaddr,
 					 iso_match_sync_handle_pa_report, ev3);
-
-		if (sk) {
-			memcpy(iso_pi(sk)->base, ev3->data, ev3->length);
-			iso_pi(sk)->base_len = ev3->length;
+		base = eir_get_service_data(ev3->data, ev3->length,
+					    EIR_BAA_SERVICE_UUID, &base_len);
+		if (base && sk && base_len <= sizeof(iso_pi(sk)->base)) {
+			memcpy(iso_pi(sk)->base, base, base_len);
+			iso_pi(sk)->base_len = base_len;
 		}
 	} else {
 		sk = iso_get_sock_listen(&hdev->bdaddr, BDADDR_ANY, NULL, NULL);
-- 
2.53.0