Bluetooth: bcsp: receive data only if registered

Currently, bcsp_recv() can be called even when the BCSP protocol has not
been registered. This leads to a NULL pointer dereference, as shown in
the following stack trace:

    KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f]
    RIP: 0010:bcsp_recv+0x13d/0x1740 drivers/bluetooth/hci_bcsp.c:590
    Call Trace:
     <TASK>
     hci_uart_tty_receive+0x194/0x220 drivers/bluetooth/hci_ldisc.c:627
     tiocsti+0x23c/0x2c0 drivers/tty/tty_io.c:2290
     tty_ioctl+0x626/0xde0 drivers/tty/tty_io.c:2706
     vfs_ioctl fs/ioctl.c:51 [inline]
     __do_sys_ioctl fs/ioctl.c:907 [inline]
     __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
     do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
     do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
     entry_SYSCALL_64_after_hwframe+0x77/0x7f

To prevent this, ensure that the HCI_UART_REGISTERED flag is set before
processing received data. If the protocol is not registered, return
-EUNATCH.

Reported-by: syzbot+4ed6852d4da4606c93da@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4ed6852d4da4606c93da
Tested-by: syzbot+4ed6852d4da4606c93da@syzkaller.appspotmail.com
Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

diff --git a/drivers/bluetooth/hci_bcsp.c b/drivers/bluetooth/hci_bcsp.c
index 664d82d1e6139a194ae3a0701caed2065b8bc27a..591abe6d63ddb5f6b98d3bd3b00fc681ec7dc628 100644 (file)
--- a/drivers/bluetooth/hci_bcsp.c
+++ b/drivers/bluetooth/hci_bcsp.c
@@ -582,6 +582,9 @@ static int bcsp_recv(struct hci_uart *hu, const void *data, int count)
        struct bcsp_struct *bcsp = hu->priv;
        const unsigned char *ptr;
 
+       if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
+               return -EUNATCH;
+
        BT_DBG("hu %p count %d rx_state %d rx_count %ld",
               hu, count, bcsp->rx_state, bcsp->rx_count);