linux-kernel - Re: [PATCH v2] efi: fix handling error value in fdt_find_uefi

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Date:   Mon, 5 Sep 2016 11:27:23 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Andrzej Hajda <a.hajda@...sung.com>
Cc:     "open list:EXTENSIBLE FIRMWARE INTERFACE (EFI)" 
        <linux-efi@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        open list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2] efi: fix handling error value in fdt_find_uefi_params

On Tue, 30 Aug, at 12:41:37PM, Andrzej Hajda wrote:
> of_get_flat_dt_subnode_by_name can return negative value in case of error.
> Assigning the result to unsigned variable and checking if the variable
> is lesser than zero is incorrect and always false.
> The patch fixes it by using signed variable to check the result.
> 
> The problem has been detected using semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci
> 
> Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
> ---
>  drivers/firmware/efi/efi.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 5a2631a..7dd2e2d 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -657,9 +657,12 @@ static int __init fdt_find_uefi_params(unsigned long node, const char *uname,
>  		}
>  
>  		if (subnode) {
> -			node = of_get_flat_dt_subnode_by_name(node, subnode);
> -			if (node < 0)
> +			int err = of_get_flat_dt_subnode_by_name(node, subnode);
> +
> +			if (err < 0)
>  				return 0;
> +
> +			node = err;
>  		}
>  
>  		return __find_uefi_params(node, info, dt_params[i].params);

Thanks Andrzej, applied.