linux-kernel - Re: [PATCH][next] mtd: rawnand: ensure return variable is initialized

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Date:   Thu, 27 May 2021 17:03:09 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] mtd: rawnand: ensure return variable is
 initialized

Hi Colin,

Colin King <colin.king@...onical.com> wrote on Thu, 27 May 2021
15:50:48 +0100:

> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently there are corner cases where spec_times is NULL and
> chip->parameters.onfi or when best_mode is zero where ret is

                       ^
something is missing here, the sentence is not clear

> not assigned a value and an uninitialized return value can be
> returned. Fix this by ensuring ret is initialized to -EINVAL.

I don't see how this situation can happen.

In both cases, no matter the value of best_mode, the for loop will
always execute at least one time (mode 0) so ret will be populated.

Maybe the robot does not know that best_mode cannot be negative and
should be defined unsigned, but the current patch is invalid.

> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: 9d3194bf2aef ("mtd: rawnand: Allow SDR timings to be nacked")
> Fixes: a9ecc8c814e9 ("mtd: rawnand: Choose the best timings, NV-DDR included")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/mtd/nand/raw/nand_base.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 57a583149cc0..18db742f650c 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -926,7 +926,7 @@ int nand_choose_best_sdr_timings(struct nand_chip *chip,
>  				 struct nand_sdr_timings *spec_timings)
>  {
>  	const struct nand_controller_ops *ops = chip->controller->ops;
> -	int best_mode = 0, mode, ret;
> +	int best_mode = 0, mode, ret = -EINVAL;
>  
>  	iface->type = NAND_SDR_IFACE;
>  
> @@ -977,7 +977,7 @@ int nand_choose_best_nvddr_timings(struct nand_chip *chip,
>  				   struct nand_nvddr_timings *spec_timings)
>  {
>  	const struct nand_controller_ops *ops = chip->controller->ops;
> -	int best_mode = 0, mode, ret;
> +	int best_mode = 0, mode, ret = 0;
>  
>  	iface->type = NAND_NVDDR_IFACE;
>  

Thanks,
Miquèl