From:   Radoslaw Biernacki <rad@semihalf.com>
To:     linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>
Cc:     CrosBT Upstreaming <chromeos-bluetooth-upstreaming@chromium.org>,
        Archie Pusaka <apusaka@chromium.org>,
        Miao-chen Chou <mcchou@chromium.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        upstream@semihalf.com, Radoslaw Biernacki <rad@semihalf.com>,
        Angela Czubak <acz@semihalf.com>,
        Marek Maslanka <mm@semihalf.com>
Subject: [PATCH] Bluetooth: Fix skb allocation in mgmt_remote_name()
Date:   Thu, 13 Jan 2022 15:08:46 +0000
Message-Id: <20220113150846.1570738-1-rad@semihalf.ocm>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Radoslaw Biernacki <rad@semihalf.com>

This patch fixes skb allocation, as lack of space for ev might push skb
tail beyond its end.
Also introduce eir_precalc_len() that can be used instead of magic
numbers for similar eir operations on skb.

Fixes: cf1bce1de7eeb ("Bluetooth: mgmt: Make use of mgmt_send_event_skb in MGMT_EV_DEVICE_FOUND")
Signed-off-by: Angela Czubak <acz@semihalf.com>
Signed-off-by: Marek Maslanka <mm@semihalf.com>
Signed-off-by: Radoslaw Biernacki <rad@semihalf.com>
---
 net/bluetooth/eir.h  |  5 +++++
 net/bluetooth/mgmt.c | 12 ++++--------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/bluetooth/eir.h b/net/bluetooth/eir.h
index 05e2e917fc25..e5876751f07e 100644
--- a/net/bluetooth/eir.h
+++ b/net/bluetooth/eir.h
@@ -15,6 +15,11 @@ u8 eir_create_scan_rsp(struct hci_dev *hdev, u8 instance, u8 *ptr);
 u8 eir_append_local_name(struct hci_dev *hdev, u8 *eir, u8 ad_len);
 u8 eir_append_appearance(struct hci_dev *hdev, u8 *ptr, u8 ad_len);
 
+static inline u16 eir_precalc_len(u8 data_len)
+{
+	return sizeof(u8) * 2 + data_len;
+}
+
 static inline u16 eir_append_data(u8 *eir, u16 eir_len, u8 type,
 				  u8 *data, u8 data_len)
 {
diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 37087cf7dc5a..d517fd847730 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -9680,13 +9680,11 @@ void mgmt_remote_name(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
 {
 	struct sk_buff *skb;
 	struct mgmt_ev_device_found *ev;
-	u16 eir_len;
-	u32 flags;
+	u16 eir_len = 0;
+	u32 flags = 0;
 
-	if (name_len)
-		skb = mgmt_alloc_skb(hdev, MGMT_EV_DEVICE_FOUND, 2 + name_len);
-	else
-		skb = mgmt_alloc_skb(hdev, MGMT_EV_DEVICE_FOUND, 0);
+	skb = mgmt_alloc_skb(hdev, MGMT_EV_DEVICE_FOUND,
+			     sizeof(*ev) + (name ? eir_precalc_len(name_len) : 0));
 
 	ev = skb_put(skb, sizeof(*ev));
 	bacpy(&ev->addr.bdaddr, bdaddr);
@@ -9696,10 +9694,8 @@ void mgmt_remote_name(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
 	if (name) {
 		eir_len = eir_append_data(ev->eir, 0, EIR_NAME_COMPLETE, name,
 					  name_len);
-		flags = 0;
 		skb_put(skb, eir_len);
 	} else {
-		eir_len = 0;
 		flags = MGMT_DEV_FOUND_NAME_REQUEST_FAILED;
 	}
 
-- 
2.34.1.703.g22d0c6ccf7-goog