linux-kernel - Re: [PATCH] arch:powerpc simple_write_to

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Date:   Fri, 5 Feb 2021 08:21:04 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Mayank Suman <mayanksuman@...e.com>, ruscur@...sell.cc,
        oohall@...il.com, mpe@...erman.id.au, benh@...nel.crashing.org,
        paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch:powerpc simple_write_to_buffer return check

Please provide some description of the change.

And please clarify the patch subject, because as far as I can see, the return is already checked 
allthough the check seams wrong.

Le 04/02/2021 à 19:16, Mayank Suman a écrit :
> Signed-off-by: Mayank Suman <mayanksuman@...e.com>
> ---
>   arch/powerpc/kernel/eeh.c                    | 8 ++++----
>   arch/powerpc/platforms/powernv/eeh-powernv.c | 4 ++--
>   2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> index 813713c9120c..2dbe1558a71f 100644
> --- a/arch/powerpc/kernel/eeh.c
> +++ b/arch/powerpc/kernel/eeh.c
> @@ -1628,8 +1628,8 @@ static ssize_t eeh_force_recover_write(struct file *filp,
>   	char buf[20];
>   	int ret;
>   
> -	ret = simple_write_to_buffer(buf, sizeof(buf), ppos, user_buf, count);
> -	if (!ret)
> +	ret = simple_write_to_buffer(buf, sizeof(buf)-1, ppos, user_buf, count);
> +	if (ret <= 0) >   		return -EFAULT;

Why return -EFAULT when the function has returned -EINVAL ?
And why is it -EFAULT when ret is 0 ? EFAULT means error accessing memory.

>   
>   	/*
> @@ -1696,7 +1696,7 @@ static ssize_t eeh_dev_check_write(struct file *filp,
>   
>   	memset(buf, 0, sizeof(buf));
>   	ret = simple_write_to_buffer(buf, sizeof(buf)-1, ppos, user_buf, count);
> -	if (!ret)
> +	if (ret <= 0)
>   		return -EFAULT;
>   
>   	ret = sscanf(buf, "%x:%x:%x.%x", &domain, &bus, &dev, &fn);
> @@ -1836,7 +1836,7 @@ static ssize_t eeh_dev_break_write(struct file *filp,
>   
>   	memset(buf, 0, sizeof(buf));
>   	ret = simple_write_to_buffer(buf, sizeof(buf)-1, ppos, user_buf, count);
> -	if (!ret)
> +	if (ret <= 0)
>   		return -EFAULT;
>   
>   	ret = sscanf(buf, "%x:%x:%x.%x", &domain, &bus, &dev, &fn);
> diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c
> index 89e22c460ebf..36ed2b8f7375 100644
> --- a/arch/powerpc/platforms/powernv/eeh-powernv.c
> +++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
> @@ -76,8 +76,8 @@ static ssize_t pnv_eeh_ei_write(struct file *filp,
>   		return -ENXIO;
>   
>   	/* Copy over argument buffer */
> -	ret = simple_write_to_buffer(buf, sizeof(buf), ppos, user_buf, count);
> -	if (!ret)
> +	ret = simple_write_to_buffer(buf, sizeof(buf)-1, ppos, user_buf, count);
> +	if (ret <= 0)
>   		return -EFAULT;
>   
>   	/* Retrieve parameters */
>