On Thu, Dec 01, 2016 at 04:28:33PM +0530, Maninder Singh wrote:
> variable name can have Non NULL terminated string after cropping
> which may result strcat to fail, and cropping is not
> required if (strlen(oh->name) + 8 < MOD_CLK_MAX_NAME_LEN).
> 
> Issue caught with static analysis tool:
> "Dangerous usage of 'name' (strncpy doesn't always 0-terminate it)"
> 
> Signed-off-by: Vaneet Narang <v.nar...@samsung.com>
> Signed-off-by: Maninder Singh <maninder...@samsung.com>
> ---
> v1 -> v2: changed strncpy to strlcpy
>  arch/arm/mach-omap2/omap_hwmod.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/omap_hwmod.c 
> b/arch/arm/mach-omap2/omap_hwmod.c
> index 759e1d4..582b95a 100644
> --- a/arch/arm/mach-omap2/omap_hwmod.c
> +++ b/arch/arm/mach-omap2/omap_hwmod.c
> @@ -742,12 +742,14 @@ static int _init_main_clk(struct omap_hwmod *oh)
>       char name[MOD_CLK_MAX_NAME_LEN];
>       struct clk *clk;
>  
> -     /* +7 magic comes from '_mod_ck' suffix */
> -     if (strlen(oh->name) + 7 > MOD_CLK_MAX_NAME_LEN)
> +     /* +8 magic comes from strlen("_mod_ck") added as suffix */
> +     if (strlen(oh->name) + 8 > MOD_CLK_MAX_NAME_LEN) {
>               pr_warn("%s: warning: cropping name for %s\n", __func__,
>                       oh->name);
> +             strlcpy(name, oh->name, MOD_CLK_MAX_NAME_LEN - 7);
> +     } else
> +             strcpy(name, oh->name);
>  
> -     strncpy(name, oh->name, MOD_CLK_MAX_NAME_LEN - 7);
>       strcat(name, "_mod_ck");
>  
>       clk = clk_get(NULL, name);
> -- 
> 1.9.1
> 

Simpler, clearer, and less error-prone:

        static const char modck[] = "_mod_ck";

        if (strlen(oh->name) >= MOD_CLK_MAX_NAME_LEN - strlen(modck))
                pr_warn("%s: warning: cropping name for %s\n", __func__,
                        oh->name);

        strlcpy(name, oh->name, MOD_CLK_MAX_NAME_LEN - strlen(modck));
        strlcat(name, modck, MOD_CLK_MAX_NAME_LEN);

Note that the length argument to strlcpy _includes_ the NUL terminator.
Also note the use of strlcat() which ensures that it won't overflow the
buffer.


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