[dpdk-dev] [RFC PATCH] use strlcpy for string copies

[Adrien Mazarguil]

On Tue, Feb 20, 2018 at 05:07:27PM +0000, Bruce Richardson wrote:
> Following on from the number of patches needing to be done for strncpy
> issues highlighted by coverity...
> 
> The strncpy function is error prone for doing "safe" string copies, so
> we generally try to use "snprintf" instead in the code. The function
> "strlcpy" is a better alternative, though, since it better conveys the
> intention of the programmer, and doesn't suffer from the non-null
> terminating behaviour of it's n'ed brethern.
> 
> The downside of this function is that it is not available by default
> on linux, though standard in the BSD's. It is available on most
> distros by installing "libbsd" package.
> 
> This RFC therefore provides the following in rte_string_fns.h to ensure
> that strlcpy is available there:
> * for BSD, include string.h as normal
> * if RTE_USE_LIBBSD is set, include <bsd/string.h>
> * if not set, fallback to snprintf for strlcpy
> 
> Using make build system, the RTE_USE_LIBBSD is a hard-coded value to "n",
> but when using meson, it's automatically set based on what is available
> on the platform.
> 
> Instances of snprintf using "%s" alone as a string format are replaced
> via coccinelle script with the new strlcpy function. Instances of
> strncpy should be replaced too, but requires manual checking as to
> whether the NULL termination is manually done afterward or not.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>

OK with the RFC, a few comments below regarding mlx4, mlx5 and the
definition itself though.

<snip>
> diff --git a/drivers/net/mlx4/mlx4_ethdev.c b/drivers/net/mlx4/mlx4_ethdev.c
> index 3bc692731..c92dd6d43 100644
> --- a/drivers/net/mlx4/mlx4_ethdev.c
> +++ b/drivers/net/mlx4/mlx4_ethdev.c
> @@ -120,7 +120,7 @@ mlx4_get_ifname(const struct priv *priv, char (*ifname)[IF_NAMESIZE])
>  			goto try_dev_id;
>  		dev_port_prev = dev_port;
>  		if (dev_port == (priv->port - 1u))
> -			snprintf(match, sizeof(match), "%s", name);
> +			strlcpy(match, name, sizeof(match));
>  	}
>  	closedir(dir);
>  	if (match[0] == '\0') {

Missing #include <rte_string_fns.h>

> diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
> index 666507691..894a045ec 100644
> --- a/drivers/net/mlx5/mlx5_ethdev.c
> +++ b/drivers/net/mlx5/mlx5_ethdev.c
> @@ -163,7 +163,7 @@ priv_get_ifname(const struct priv *priv, char (*ifname)[IF_NAMESIZE])
>  			goto try_dev_id;
>  		dev_port_prev = dev_port;
>  		if (dev_port == (priv->port - 1u))
> -			snprintf(match, sizeof(match), "%s", name);
> +			strlcpy(match, name, sizeof(match));
>  	}
>  	closedir(dir);
>  	if (match[0] == '\0')

Ditto (note I didn't check missing occurrences in other components).

<snip>
> diff --git a/lib/librte_eal/common/include/rte_string_fns.h b/lib/librte_eal/common/include/rte_string_fns.h
> index e97047a47..ff4c98b2a 100644
> --- a/lib/librte_eal/common/include/rte_string_fns.h
> +++ b/lib/librte_eal/common/include/rte_string_fns.h
> @@ -45,6 +45,20 @@ int
>  rte_strsplit(char *string, int stringlen,
>               char **tokens, int maxtokens, char delim);
>  
> +/* pull in a strlcpy function */
> +#ifdef RTE_EXEC_ENV_BSDAPP
> +#include <string.h>
> +
> +#else /* non-BSD platforms */
> +#ifdef RTE_USE_LIBBSD
> +#include <bsd/string.h>
> +
> +#else /* no BSD header files, create own */
> +#define strlcpy(dst, src, size) snprintf(dst, size, "%s", src)

Missing #include <stdio.h> for that.

What also bothers me is that on some platforms, applications get a true
function definition and a macro on others. I suggest a static inline
or even a proper versioned definition in eal_common_string_fns.c instead.

-- 
Adrien Mazarguil
6WIND