[PATCH 6.6.y] Bluetooth: eir: Fix possible crashes on eir_create_adv_data

[Artem Dinaburg <artem@trailofbits.com>]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

[ Upstream commit 47c03902269aff377f959dc3fd94a9733aa31d6e ]

eir_create_adv_data may attempt to add EIR_FLAGS and EIR_TX_POWER
without checking if that would fit.

Link: https://github.com/bluez/bluez/issues/1117#issuecomment-2958244066
Fixes: 01ce70b0a274 ("Bluetooth: eir: Move EIR/Adv Data functions to its own file")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Assisted-by: LLM
[ Backport to 6.6.y: The extended advertising PDU is stack allocated here,
  rather than addressed through pdu->data. Pass pdu.data and
  sizeof(pdu.data), the actual HCI_MAX_EXT_AD_LENGTH capacity, so all
  optional advertising additions remain bounded by their caller buffer. ]
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
Hi,

Please consider this backport of the fix for CVE-2025-38303 to 6.6.y.

The code changes follow upstream, except the extended advertising call
uses its stack buffer and sizeof(pdu.data); see the backport note.

The complete fix is already present in 6.12.y, 6.18.y and 7.2.y.

Build-tested only as part of a cumulative 6.6.y series on x86_64
(allmodconfig, CONFIG_WERROR=y); no runtime testing.

Thanks,
Artem Dinaburg

 net/bluetooth/eir.c      |    7 ++++---
 net/bluetooth/eir.h      |    2 +-
 net/bluetooth/hci_sync.c |    5 +++--
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/eir.c b/net/bluetooth/eir.c
index 7a28baa2b71feccc8bd7ff3f1d45b6b1f39984f7..2f695f1c69b36b129d9e52ed1453c91f3e2662b0 100644
--- a/net/bluetooth/eir.c
+++ b/net/bluetooth/eir.c
@@ -242,7 +242,7 @@ u8 eir_create_per_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr)
 	return ad_len;
 }
 
-u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr)
+u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size)
 {
 	struct adv_info *adv = NULL;
 	u8 ad_len = 0, flags = 0;
@@ -286,7 +286,7 @@ u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr)
 		/* If flags would still be empty, then there is no need to
 		 * include the "Flags" AD field".
 		 */
-		if (flags) {
+		if (flags && (ad_len + eir_precalc_len(1) <= size)) {
 			ptr[0] = 0x02;
 			ptr[1] = EIR_FLAGS;
 			ptr[2] = flags;
@@ -316,7 +316,8 @@ skip_flags:
 		}
 
 		/* Provide Tx Power only if we can provide a valid value for it */
-		if (adv_tx_power != HCI_TX_POWER_INVALID) {
+		if (adv_tx_power != HCI_TX_POWER_INVALID &&
+		    (ad_len + eir_precalc_len(1) <= size)) {
 			ptr[0] = 0x02;
 			ptr[1] = EIR_TX_POWER;
 			ptr[2] = (u8)adv_tx_power;
diff --git a/net/bluetooth/eir.h b/net/bluetooth/eir.h
index 0df19f2f4af94499defe78897e8c78fd0dbc2daf..4497f8fd5fefb5eed4d70477fb0fdf9feebe7fe4 100644
--- a/net/bluetooth/eir.h
+++ b/net/bluetooth/eir.h
@@ -9,7 +9,7 @@
 
 void eir_create(struct hci_dev *hdev, u8 *data);
 
-u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr);
+u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size);
 u8 eir_create_scan_rsp(struct hci_dev *hdev, u8 instance, u8 *ptr);
 u8 eir_create_per_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr);
 
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 607667cc357558ffefa812e1cf001ca923fdbf78..e73b4021dc6505924d6befaf667dadcaca6f0526 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -1334,7 +1334,8 @@ static int hci_set_ext_adv_data_sync(struct hci_dev *hdev, u8 instance)
 		}
 	}
 
-	len = eir_create_adv_data(hdev, instance, pdu.data);
+	len = eir_create_adv_data(hdev, instance, pdu.data,
+				  sizeof(pdu.data));
 
 	pdu.cp.length = len;
 	pdu.cp.handle = instance;
@@ -1376,7 +1377,7 @@ static int hci_set_adv_data_sync(struct hci_dev *hdev, u8 instance)
 
 	memset(&cp, 0, sizeof(cp));
 
-	len = eir_create_adv_data(hdev, instance, cp.data);
+	len = eir_create_adv_data(hdev, instance, cp.data, sizeof(cp.data));
 
 	/* There's nothing to do if the data hasn't changed */
 	if (hdev->adv_data_len == len &&