linux-kernel - Re: [PATCH 3/5] switchtec: A temporary variable should be used for the flags of switchtec_ioctl_event

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Date:   Wed, 12 Dec 2018 16:43:15 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Wesley Sheng <wesley.sheng@...rochip.com>
Cc:     kurt.schwemmer@...rosemi.com, logang@...tatee.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        wesleyshenggit@...a.com
Subject: Re: [PATCH 3/5] switchtec: A temporary variable should be used for
 the flags of switchtec_ioctl_event_ctl

On Mon, Dec 10, 2018 at 05:12:22PM +0800, Wesley Sheng wrote:
> From: Joey Zhang <joey.zhang@...rochip.com>
> 
> For nr_idxs is larger than 1 switchtec_ioctl_event_ctl event flags will be
> used by each event indexes. In current implementation the event flags are
> overwritten by first call of the function event_ctl().
> 
> Preserve the event flag value with a temporary variable.
> 
> Fixes: 52eabba5bcdb ("switchtec: Add IOCTLs to the Switchtec driver")
> Signed-off-by: Joey Zhang <joey.zhang@...rochip.com>
> Signed-off-by: Wesley Sheng <wesley.sheng@...rochip.com>
> Reviewed-by: Logan Gunthorpe <logang@...tatee.com>
> ---
>  drivers/pci/switch/switchtec.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
> index 480107e..a908670 100644
> --- a/drivers/pci/switch/switchtec.c
> +++ b/drivers/pci/switch/switchtec.c
> @@ -796,6 +796,7 @@ static int ioctl_event_ctl(struct switchtec_dev *stdev,
>  {
>  	int ret;
>  	int nr_idxs;
> +	unsigned int event_flags;
>  	struct switchtec_ioctl_event_ctl ctl;
>  
>  	if (copy_from_user(&ctl, uctl, sizeof(ctl)))
> @@ -817,7 +818,9 @@ static int ioctl_event_ctl(struct switchtec_dev *stdev,
>  		else
>  			return -EINVAL;
>  
> +		event_flags = ctl.flags;
>  		for (ctl.index = 0; ctl.index < nr_idxs; ctl.index++) {
> +			ctl.flags = event_flags;
>  			ret = event_ctl(stdev, &ctl);

event_ctl() overwrites several other things, in addition to ctl.flags:

  ctl.data[]
  ctl.occurred
  ctl.count

Is that what you intend?  It looks like only the values from the *last*
call of event_ctl() will be copied back to the user buffer.

>  			if (ret < 0)
>  				return ret;
> -- 
> 2.7.4
>