[PATCH AUTOSEL 5.0 128/262] Bluetooth: hci_ldisc: Initialize hci_dev before open()

[Sasha Levin]

From: Jeremy Cline <jcl...@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+257790c15bcdef6fe...@syzkaller.appspotmail.com
Signed-off-by: Jeremy Cline <jcl...@redhat.com>
Signed-off-by: Marcel Holtmann <mar...@holtmann.org>
Signed-off-by: Sasha Levin <sas...@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 fbf7b4df23ab..4918fefc4a6f 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -207,11 +207,11 @@ 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;
        }
 
@@ -616,6 +616,7 @@ 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("");
 
@@ -659,11 +660,22 @@ 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;
@@ -683,17 +695,12 @@ 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