Em Mon, 21 Mar 2016 14:30:22 +0100
Max Kellermann <m...@duempel.org> escreveu:
> Fixes use-after-free bug which occurs when I disconnect my DVB-S
> received while VDR is running.
I guess that the best way to fix it is to use a kref() that would be also
incremented at open() and decremented at release().
This works better than adding other non-standard ways to manage data livetime
cycle.
Regards,
Mauro
>
> Signed-off-by: Max Kellermann <m...@duempel.org>
> ---
> drivers/media/dvb-core/dvb_ca_en50221.c | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c
> b/drivers/media/dvb-core/dvb_ca_en50221.c
> index e33364c..dfc686a 100644
> --- a/drivers/media/dvb-core/dvb_ca_en50221.c
> +++ b/drivers/media/dvb-core/dvb_ca_en50221.c
> @@ -148,6 +148,9 @@ struct dvb_ca_private {
> /* Flag indicating if the CA device is open */
> unsigned int open:1;
>
> + /* Flag indicating if the CA device is released */
> + unsigned int released:1;
> +
> /* Flag indicating the thread should wake up now */
> unsigned int wakeup:1;
>
> @@ -1392,6 +1395,11 @@ static int dvb_ca_en50221_io_read_condition(struct
> dvb_ca_private *ca,
> int found = 0;
> u8 hdr[2];
>
> + if (ca->released) {
> + *result = -ENODEV;
> + return 1;
> + }
> +
> slot = ca->next_read_slot;
> while ((slot_count < ca->slot_count) && (!found)) {
> if (ca->slot_info[slot].slot_state != DVB_CA_SLOTSTATE_RUNNING)
> @@ -1595,6 +1603,9 @@ static int dvb_ca_en50221_io_release(struct inode
> *inode, struct file *file)
>
> err = dvb_generic_release(inode, file);
>
> + if (ca->released)
> + dvb_ca_private_free(ca);
> +
> module_put(ca->pub->owner);
>
> return err;
> @@ -1701,6 +1712,7 @@ int dvb_ca_en50221_init(struct dvb_adapter *dvb_adapter,
> }
> init_waitqueue_head(&ca->wait_queue);
> ca->open = 0;
> + ca->released = 0;
> ca->wakeup = 0;
> ca->next_read_slot = 0;
> pubca->private = ca;
> @@ -1765,12 +1777,21 @@ void dvb_ca_en50221_release(struct dvb_ca_en50221
> *pubca)
>
> dprintk("%s\n", __func__);
>
> + BUG_ON(ca->released);
> +
> /* shutdown the thread if there was one */
> kthread_stop(ca->thread);
>
> for (i = 0; i < ca->slot_count; i++) {
> dvb_ca_en50221_slot_shutdown(ca, i);
> }
> - dvb_ca_private_free(ca);
> +
> + if (ca->open) {
> + ca->released = 1;
> + mb();
> + wake_up_interruptible(&ca->wait_queue);
> + } else
> + dvb_ca_private_free(ca);
> +
> pubca->private = NULL;
> }
>
> --
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--
Thanks,
Mauro
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