netdev - Re: [PATCH net 1/2] gen_stats.c: Duplicate xstats buffer for later use

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Message-ID: <54AE812E.4070508@cogentembedded.com>
Date:	Thu, 08 Jan 2015 16:07:58 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Ignacy Gawędzki 
	<ignacy.gawedzki@...en-communications.fr>, netdev@...r.kernel.org
Subject: Re: [PATCH net 1/2] gen_stats.c: Duplicate xstats buffer for later
 use

Hello.

On 1/8/2015 1:35 PM, Ignacy Gawędzki wrote:

> The gnet_stats_copy_app() function gets called, more often than not, with its
> second argument a pointer to an automatic variable in the caller's stack.
> Therefore, to avoid copying garbage afterwards when calling
> gnet_stats_finish_copy(), this data is better copied to a dynamically allocated
> memory that gets freed after use.

> Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@...en-communications.fr>
> ---
>   net/core/gen_stats.c | 17 ++++++++++++++---
>   1 file changed, 14 insertions(+), 3 deletions(-)

> diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
> index 0c08062..5770a0e 100644
> --- a/net/core/gen_stats.c
> +++ b/net/core/gen_stats.c
> @@ -305,7 +305,10 @@ int
>   gnet_stats_copy_app(struct gnet_dump *d, void *st, int len)
>   {
>   	if (d->compat_xstats) {
> -		d->xstats = st;
> +		d->xstats = kmalloc(len, GFP_KERNEL);
> +		if (!d->xstats)
> +			goto kmalloc_failure;
> +		memcpy(d->xstats, st, len);

    Please use kmemdup() instead of kmalloc()/memcpy().

[...]

WBR, Sergei

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