[PATCH AUTOSEL 4.14 061/123] Bluetooth: hci_ldisc: Initialize hci_dev before open()

[PATCH AUTOSEL 4.14 061/123] Bluetooth: hci_ldisc: Initialize hci_dev before open()

[Sasha Levin]

From: Jeremy Cline <jcline@redhat.com>

[ Upstream commit 32a7b4cbe93b0a0ef7e63d31ca69ce54736c4412 ]

The hci_dev struct hdev is referenced in work queues and timers started
by open() in some protocols. This creates a race between the
initialization function and the work or timer which can result hdev
being dereferenced while it is still null.

The syzbot report contains a reliable reproducer which causes a null
pointer dereference of hdev in hci_uart_write_work() by making the
memory allocation for hdev fail.

To fix this, ensure hdev is valid from before calling a protocol's
open() until after calling a protocol's close().

Reported-by: syzbot+257790c15bcdef6fe00c@syzkaller.appspotmail.com
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/bluetooth/hci_ldisc.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 30bbe19b4b85..6a3a3011b38e 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -207,11 +207,11 @@ static void hci_uart_init_work(struct work_struct *work)
 	err = hci_register_dev(hu->hdev);
 	if (err < 0) {
 		BT_ERR("Can't register HCI device");
+		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
+		hu->proto->close(hu);
 		hdev = hu->hdev;
 		hu->hdev = NULL;
 		hci_free_dev(hdev);
-		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
-		hu->proto->close(hu);
 		return;
 	}
 
@@ -612,6 +612,7 @@ static void hci_uart_tty_receive(struct tty_struct *tty, const u8 *data,
 static int hci_uart_register_dev(struct hci_uart *hu)
 {
 	struct hci_dev *hdev;
+	int err;
 
 	BT_DBG("");
 
@@ -655,11 +656,22 @@ static int hci_uart_register_dev(struct hci_uart *hu)
 	else
 		hdev->dev_type = HCI_PRIMARY;
 
+	/* Only call open() for the protocol after hdev is fully initialized as
+	 * open() (or a timer/workqueue it starts) may attempt to reference it.
+	 */
+	err = hu->proto->open(hu);
+	if (err) {
+		hu->hdev = NULL;
+		hci_free_dev(hdev);
+		return err;
+	}
+
 	if (test_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags))
 		return 0;
 
 	if (hci_register_dev(hdev) < 0) {
 		BT_ERR("Can't register HCI device");
+		hu->proto->close(hu);
 		hu->hdev = NULL;
 		hci_free_dev(hdev);
 		return -ENODEV;
@@ -679,17 +691,12 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)
 	if (!p)
 		return -EPROTONOSUPPORT;
 
-	err = p->open(hu);
-	if (err)
-		return err;
-
 	hu->proto = p;
 	set_bit(HCI_UART_PROTO_READY, &hu->flags);
 
 	err = hci_uart_register_dev(hu);
 	if (err) {
 		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
-		p->close(hu);
 		return err;
 	}
 
-- 
2.19.1

[PATCH AUTOSEL 4.14 104/123] Bluetooth: Verify that l2cap_get_conf_opt provides large enough buffer

[Sasha Levin]

From: Marcel Holtmann <marcel@holtmann.org>

[ Upstream commit 7c9cbd0b5e38a1672fcd137894ace3b042dfbf69 ]

The function l2cap_get_conf_opt will return L2CAP_CONF_OPT_SIZE + opt->len
as length value. The opt->len however is in control over the remote user
and can be used by an attacker to gain access beyond the bounds of the
actual packet.

To prevent any potential leak of heap memory, it is enough to check that
the resulting len calculation after calling l2cap_get_conf_opt is not
below zero. A well formed packet will always return >= 0 here and will
end with the length value being zero after the last option has been
parsed. In case of malformed packets messing with the opt->len field the
length value will become negative. If that is the case, then just abort
and ignore the option.

In case an attacker uses a too short opt->len value, then garbage will
be parsed, but that is protected by the unknown option handling and also
the option parameter size checks.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/bluetooth/l2cap_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 9b7907ebfa01..7a8a58af8c98 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -3336,6 +3336,8 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
 
 	while (len >= L2CAP_CONF_OPT_SIZE) {
 		len -= l2cap_get_conf_opt(&req, &type, &olen, &val);
+		if (len < 0)
+			break;
 
 		hint  = type & L2CAP_CONF_HINT;
 		type &= L2CAP_CONF_MASK;
@@ -3547,6 +3549,8 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
 
 	while (len >= L2CAP_CONF_OPT_SIZE) {
 		len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);
+		if (len < 0)
+			break;
 
 		switch (type) {
 		case L2CAP_CONF_MTU:
@@ -3727,6 +3731,8 @@ static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len)
 
 	while (len >= L2CAP_CONF_OPT_SIZE) {
 		len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);
+		if (len < 0)
+			break;
 
 		switch (type) {
 		case L2CAP_CONF_RFC:
-- 
2.19.1