linux-kernel - Re: [PATCH 1/4] misc: xilinx_sdfec: Fix a couple small information leaks

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Date:   Thu, 22 Aug 2019 10:14:12 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michal Simek <michal.simek@...inx.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 1/4] misc: xilinx_sdfec: Fix a couple small information
 leaks

Hi Dan,

On 21. 08. 19 9:06, Dan Carpenter wrote:
> These structs have holes in them so we end up disclosing a few bytes of
> uninitialized stack data.
> 
> drivers/misc/xilinx_sdfec.c:305 xsdfec_get_status() warn: check that 'status' doesn't leak information (struct has a hole after 'activity')
> drivers/misc/xilinx_sdfec.c:449 xsdfec_get_turbo() warn: check that 'turbo_params' doesn't leak information (struct has a hole after 'scale')

Who is generating these warnings? Is this any new GCC or different tool?
I see that 3byte padding but never seen these warnings.

> We need to zero out the holes with memset().
> 
> Fixes: 6bd6a690c2e7 ("misc: xilinx_sdfec: Add stats & status ioctls")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>  drivers/misc/xilinx_sdfec.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/misc/xilinx_sdfec.c b/drivers/misc/xilinx_sdfec.c
> index 912e939dec62..dc1b8b412712 100644
> --- a/drivers/misc/xilinx_sdfec.c
> +++ b/drivers/misc/xilinx_sdfec.c
> @@ -295,6 +295,7 @@ static int xsdfec_get_status(struct xsdfec_dev *xsdfec, void __user *arg)
>  	struct xsdfec_status status;
>  	int err;
>  
> +	memset(&status, 0, sizeof(status));
>  	spin_lock_irqsave(&xsdfec->error_data_lock, xsdfec->flags);
>  	status.state = xsdfec->state;
>  	xsdfec->state_updated = false;
> @@ -440,6 +441,7 @@ static int xsdfec_get_turbo(struct xsdfec_dev *xsdfec, void __user *arg)
>  	if (xsdfec->config.code == XSDFEC_LDPC_CODE)
>  		return -EIO;
>  
> +	memset(&turbo_params, 0, sizeof(turbo_params));
>  	reg_value = xsdfec_regread(xsdfec, XSDFEC_TURBO_ADDR);
>  
>  	turbo_params.scale = (reg_value & XSDFEC_TURBO_SCALE_MASK) >>
> 

Reviewed-by: Michal Simek <michal.simek@...inx.com>

Thanks,
Michal