ACK: [PATCH] lib: fwts_modprobe: add helper to build module path name

[ivanhu]

On 7/28/20 6:46 PM, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> The current method of building a module pathname may cause truncation
> and gcc-10 generates build errors because of this. Add a helper that
> builds the module path that uses the BSD strlcat for safe string
> concatenation with known (and ignored) truncation since we know that
> the module path name can't exceed PATH_MAX size.
> 
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>  src/lib/src/fwts_modprobe.c | 32 +++++++++++++++++++++++++++++---
>  1 file changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/src/lib/src/fwts_modprobe.c b/src/lib/src/fwts_modprobe.c
> index ace2f50c..492bf9b4 100644
> --- a/src/lib/src/fwts_modprobe.c
> +++ b/src/lib/src/fwts_modprobe.c
> @@ -28,9 +28,36 @@
>  #include <stdlib.h>
>  #include <errno.h>
>  #include <sys/utsname.h>
> +#include <bsd/string.h>
>  
>  #include "fwts.h"
>  
> +/*
> + *  fwts_module_path()
> + *	build a new path based on basename path and
> + *	the new filename (or directory name)
> + */
> +static void fwts_module_path(
> +	char *newpath,
> +	const size_t newpath_len,
> +	const char *basepath,
> +	const char *filename)
> +{
> +	char *ptr = newpath;
> +	size_t n = newpath_len, len;
> +
> +	(void)strlcpy(ptr, basepath, n);
> +	len = strlen(basepath);
> +	ptr += len;
> +	n -= len;
> +
> +	(void)strlcpy(ptr, "/", n);
> +	ptr++;
> +	n--;
> +
> +	(void)strlcpy(ptr, filename, n);
> +}
> +
>  /*
>   *  fwts_module_find()
>   *	recursively search for module from the basepath start
> @@ -59,8 +86,7 @@ static bool fwts_module_find(
>  
>  		switch (de->d_type) {
>  		case DT_DIR:
> -			(void)snprintf(newpath, sizeof(newpath), "%s/%s",
> -				basepath, de->d_name);
> +			fwts_module_path(newpath, sizeof(newpath), basepath, de->d_name);
>  			if (fwts_module_find(module, newpath, path, path_len)) {
>  				(void)closedir(dir);
>  				return true;
> @@ -68,7 +94,7 @@ static bool fwts_module_find(
>  			break;
>  		case DT_REG:
>  			if (!strcmp(de->d_name, module)) {
> -				(void)snprintf(path, path_len, "%s/%s", basepath, module);
> +				fwts_module_path(path, path_len, basepath, module);
>  				(void)closedir(dir);
>  				return true;
>  			}
> 

Acked-by: Ivan Hu <ivan.hu at canonical.com>