From: Alan Cox <[email protected]>

commit c19483cc5e56ac5e22dd19cf25ba210ab1537773 upstream.

Fortunately this is only exploitable on very unusual hardware.

[Reported a while ago but nothing happened so just fixing it]

Signed-off-by: Alan Cox <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Paul Gortmaker <[email protected]>
---
 drivers/bluetooth/hci_ldisc.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 76a1abb..283b127 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -258,9 +258,16 @@ static int hci_uart_tty_open(struct tty_struct *tty)
 
        BT_DBG("tty %p", tty);
 
+       /* FIXME: This btw is bogus, nothing requires the old ldisc to clear
+          the pointer */
        if (hu)
                return -EEXIST;
 
+       /* Error if the tty has no write op instead of leaving an exploitable
+          hole */
+       if (tty->ops->write == NULL)
+               return -EOPNOTSUPP;
+
        if (!(hu = kzalloc(sizeof(struct hci_uart), GFP_KERNEL))) {
                BT_ERR("Can't allocate control structure");
                return -ENFILE;
-- 
1.7.3.3

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