Re: [PATCH v3] char: pcmcia: synclink_cs: Fix use-after-free in mgslpc_ops

Ilpo Järvinen
2022-09-16T13:55:20Z

On Fri, 16 Sep 2022, Hyunwoo Kim wrote:

> A race condition may occur if the user physically removes
> the pcmcia device while calling ioctl() for this tty device node.
>
> This is a race condition between the mgslpc_ioctl() function and
> the mgslpc_detach() function, which may eventually result in UAF.
>
> So, add a refcount check to mgslpc_detach() to free the structure
> after the tty device node is close()d.
>
> Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>

> @@ -2517,9 +2548,14 @@ static int mgslpc_open(struct tty_struct *tty, struct file * filp)
> if (debug_level >= DEBUG_LEVEL_INFO)
> printk("%s(%d):mgslpc_open(%s) success\n",
> __FILE__, __LINE__, info->device_name);
> +
> + kref_get(&info->refcnt);
> retval = 0;
> + mutex_unlock(&remove_mutex);
>
> + return retval;
> cleanup:
> + mutex_unlock(&remove_mutex);
> return retval;

Just move the cleanup label instead.

--
i.