[PATCH] checkpatch: Add warnings for using strn(cat|cpy)

[Tom Rini]

On Wed, Mar 10, 2021 at 08:45:27PM -0500, Sean Anderson wrote:
> strn(cat|cpy) has a bad habit of not nul-terminating the destination,
> resulting in constructions like
> 
> 	strncpy(foo, bar, sizeof(foo) - 1);
> 	foo[sizeof(foo) - 1] = '\0';
> 
> However, it is very easy to forget about this behavior and accidentally
> leave a string unterminated. This has shown up in some recent coverity
> scans [1, 2] (including code recently touched by yours truly).
> 
> Fortunately, the guys at OpenBSD came up with strl(cat|cpy), which always
> nul-terminate strings. These functions are already in U-Boot, so we should
> encourage new code to use them instead of strn(cat|cpy).
> 
> [1] https://lists.denx.de/pipermail/u-boot/2021-March/442888.html
> [2] https://lists.denx.de/pipermail/u-boot/2021-January/438073.html
> 
> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
> ---
> 
>  scripts/checkpatch.pl           |  6 ++++++
>  tools/patman/test_checkpatch.py | 14 +++++++++++++-
>  2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 755f4802a4..91365a5529 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -5892,6 +5892,12 @@ sub process {
>  			}
>  		}
>  
> +# prefer strl(cpy|cat) over strn(cpy|cat)
> +		if ($line =~ /\bstrn(cpy|cat)\s*\(/) {
> +			WARN("STRL",
> +			     "strl$1 is preferred over strn$1 because it always produces a nul-terminated string\n" . $herecurr);
> +		}
> +
>  # prefer usleep_range over udelay
>  		if ($line =~ /\budelay\s*\(\s*(\d+)\s*\)/) {
>  			my $delay = $1;

This needs to be in the u-boot specific checks section (starting at
around line 2300) as I assume Linux won't really want this.  Thanks!

-- 
Tom
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