ipack: ipoctal: fix tty-registration error handling

Registration of the ipoctal tty devices is unlikely to fail, but if it
ever does, make sure not to deregister a never registered tty device
(and dereference a NULL pointer) when the driver is later unbound.

Fixes: 2afb41d9d30d ("Staging: ipack/devices/ipoctal: Check tty_register_device return value.")
Cc: stable@vger.kernel.org      # 3.7
Acked-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210917114622.5412-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/ipack/devices/ipoctal.c b/drivers/ipack/devices/ipoctal.c
index 2624513..d6875aa 100644 (file)
--- a/drivers/ipack/devices/ipoctal.c
+++ b/drivers/ipack/devices/ipoctal.c
@@ -33,6 +33,7 @@ struct ipoctal_channel {
        unsigned int                    pointer_read;
        unsigned int                    pointer_write;
        struct tty_port                 tty_port;
+       bool                            tty_registered;
        union scc2698_channel __iomem   *regs;
        union scc2698_block __iomem     *block_regs;
        unsigned int                    board_id;
@@ -396,9 +397,11 @@ static int ipoctal_inst_slot(struct ipoctal *ipoctal, unsigned int bus_nr,
                                                        i, NULL, channel, NULL);
                if (IS_ERR(tty_dev)) {
                        dev_err(&ipoctal->dev->dev, "Failed to register tty device.\n");
+                       tty_port_free_xmit_buf(&channel->tty_port);
                        tty_port_destroy(&channel->tty_port);
                        continue;
                }
+               channel->tty_registered = true;
        }
 
        /*
@@ -698,6 +701,10 @@ static void __ipoctal_remove(struct ipoctal *ipoctal)
 
        for (i = 0; i < NR_CHANNELS; i++) {
                struct ipoctal_channel *channel = &ipoctal->channel[i];
+
+               if (!channel->tty_registered)
+                       continue;
+
                tty_unregister_device(ipoctal->tty_drv, i);
                tty_port_free_xmit_buf(&channel->tty_port);
                tty_port_destroy(&channel->tty_port);