On 06/07/2021 16:50, Pavel Skripkin wrote:
> Syzbot reported corrupted list in em28xx driver. The problem was in
> non-reinitialized lists on disconnect. Since all 2 lists are global
> variables and driver can be connected and disconnected many times we
> should call INIT_LIST_HEAD() in .disconnect method to prevent corrupted
> list entries.
>
> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
> Reported-by: syzbot+a6969ef522a36d3344c9@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
> ---
> drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
> drivers/media/usb/em28xx/em28xx-core.c | 6 ++++++
> drivers/media/usb/em28xx/em28xx.h | 1 +
> 3 files changed, 9 insertions(+)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index ba9292e2a587..8b1ff79c37a0 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4148,6 +4148,8 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
> dev->dev_next = NULL;
> }
> kref_put(&dev->ref, em28xx_free_device);
> +
> + em28xx_reset_lists();
> }
>
> static int em28xx_usb_suspend(struct usb_interface *intf,
> diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
> index 584fa400cd7d..03970ed00dba 100644
> --- a/drivers/media/usb/em28xx/em28xx-core.c
> +++ b/drivers/media/usb/em28xx/em28xx-core.c
> @@ -1131,6 +1131,12 @@ void em28xx_init_extension(struct em28xx *dev)
> mutex_unlock(&em28xx_devlist_mutex);
> }
>
> +void em28xx_reset_lists(void)
> +{
> + INIT_LIST_HEAD(&em28xx_devlist);
> + INIT_LIST_HEAD(&em28xx_extension_devlist);
This needs a mutex_lock(&em28xx_devlist_mutex);
But actually, I don't think this is right: if there are multiple em28xx
devices, then I think if you disconnect one, then the other is - with this
code - also removed from the list.
Can you give a link to the actual syzbot bug? I'm not at all sure you are
fixing the right thing here.
Regards,
Hans
> +}
> +
> void em28xx_close_extension(struct em28xx *dev)
> {
> const struct em28xx_ops *ops = NULL;
> diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
> index ab167cd1f400..73caaaa398d3 100644
> --- a/drivers/media/usb/em28xx/em28xx.h
> +++ b/drivers/media/usb/em28xx/em28xx.h
> @@ -835,6 +835,7 @@ void em28xx_stop_urbs(struct em28xx *dev);
> int em28xx_set_mode(struct em28xx *dev, enum em28xx_mode set_mode);
> int em28xx_gpio_set(struct em28xx *dev, const struct em28xx_reg_seq *gpio);
> int em28xx_register_extension(struct em28xx_ops *dev);
> +void em28xx_reset_lists(void);
> void em28xx_unregister_extension(struct em28xx_ops *dev);
> void em28xx_init_extension(struct em28xx *dev);
> void em28xx_close_extension(struct em28xx *dev);
>
