[PATCH] firewire: cdev: fix potential leak of kernel stack due to uninitialized value

[Takashi Sakamoto]

Hi Iwai-san,

I have a moderate request to you for the patch which fixes an issue
included in v5.19-rc1. If it's applicable and I can borrow your help
again, I'd like you to send the patch to mainline via your tree.

If possible, it's preferable to apply additional three patches I
respined[1], but it could be optional since not so critical.

[1] https://lore.kernel.org/alsa-devel/20220512111756.103008-1-o-takashi@sakamocchi.jp/

On Thu, May 12, 2022 at 08:20:37PM +0900, Takashi Sakamoto wrote:
> Recent change brings potential leak of value on kernel stack to userspace
> due to uninitialized value.
> 
> This commit fixes the bug.
> 
> Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
> Fixes: baa914cd81f ("firewire: add kernel API to access CYCLE_TIME register")
> Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
> ---
>  drivers/firewire/core-cdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
> index 8e9670036e5c..032ee56c34a3 100644
> --- a/drivers/firewire/core-cdev.c
> +++ b/drivers/firewire/core-cdev.c
> @@ -1211,7 +1211,7 @@ static int ioctl_get_cycle_timer2(struct client *client, union ioctl_arg *arg)
>  	struct fw_cdev_get_cycle_timer2 *a = &arg->get_cycle_timer2;
>  	struct fw_card *card = client->device->card;
>  	struct timespec64 ts = {0, 0};
> -	u32 cycle_time;
> +	u32 cycle_time = 0;
>  	int ret = 0;
>  
>  	local_irq_disable();
> -- 
> 2.34.1


Thanks

Takashi Sakamoto