linux-kernel - Re: [PATCH] ocxl: fix signed comparison with less than zero

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Message-Id: <7960dfb3-3e56-5e22-548b-322e1c741495@au1.ibm.com>
Date:   Wed, 31 Jan 2018 10:42:47 +1100
From:   Andrew Donnellan <andrew.donnellan@....ibm.com>
To:     Colin King <colin.king@...onical.com>,
        Frederic Barrat <fbarrat@...ux.vnet.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ocxl: fix signed comparison with less than zero

On 31/01/18 02:11, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the comparison of used < 0 is always false because
> uses is a size_t. Fix this by making used a ssize_t type.
> 
> Detected by Coccinelle:
> drivers/misc/ocxl/file.c:320:6-10: WARNING: Unsigned expression
> compared with zero: used < 0
> 
> Fixes: 5ef3166e8a32 ("ocxl: Driver code for 'generic' opencapi devices")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Thanks for picking this up!

Acked-by: Andrew Donnellan <andrew.donnellan@....ibm.com>

> ---
>   drivers/misc/ocxl/file.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/ocxl/file.c b/drivers/misc/ocxl/file.c
> index c90c1a578d2f..1287e4430e6b 100644
> --- a/drivers/misc/ocxl/file.c
> +++ b/drivers/misc/ocxl/file.c
> @@ -277,7 +277,7 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
>   	struct ocxl_context *ctx = file->private_data;
>   	struct ocxl_kernel_event_header header;
>   	ssize_t rc;
> -	size_t used = 0;
> +	ssize_t used = 0;
>   	DEFINE_WAIT(event_wait);
>   
>   	memset(&header, 0, sizeof(header));
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@....ibm.com  IBM Australia Limited