NFC: nci: uart: Set tty->disc_data only in success path

commit fc27ab48904ceb7e4792f0c400f1ef175edf16fe upstream.

Setting tty->disc_data before opening the NCI device means we need to
clean it up on error paths.  This also opens some short window if device
starts sending data, even before NCIUARTSETDRIVER IOCTL succeeded
(broken hardware?).  Close the window by exposing tty->disc_data only on
the success path, when opening of the NCI device and try_module_get()
succeeds.

The code differs in error path in one aspect: tty->disc_data won't be
ever assigned thus NULL-ified.  This however should not be relevant
difference, because of "tty->disc_data=NULL" in nci_uart_tty_open().

Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Fixes: 9961127d4bce ("NFC: nci: add generic uart support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/20250618073649.25049-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/nfc/nci/uart.c b/net/nfc/nci/uart.c
index 1204c438e87dc5ce92200f39f9888615923bb96b..03a51bcb9c3733639b8e7e8160daed70f4a85021 100644 (file)
--- a/net/nfc/nci/uart.c
+++ b/net/nfc/nci/uart.c
@@ -131,22 +131,22 @@ static int nci_uart_set_driver(struct tty_struct *tty, unsigned int driver)
 
        memcpy(nu, nci_uart_drivers[driver], sizeof(struct nci_uart));
        nu->tty = tty;
-       tty->disc_data = nu;
        skb_queue_head_init(&nu->tx_q);
        INIT_WORK(&nu->write_work, nci_uart_write_work);
        spin_lock_init(&nu->rx_lock);
 
        ret = nu->ops.open(nu);
        if (ret) {
-               tty->disc_data = NULL;
                kfree(nu);
+               return ret;
        } else if (!try_module_get(nu->owner)) {
                nu->ops.close(nu);
-               tty->disc_data = NULL;
                kfree(nu);
                return -ENOENT;
        }
-       return ret;
+       tty->disc_data = nu;
+
+       return 0;
 }
 
 /* ------ LDISC part ------ */