Re: [PATCH v2] column: disallow negative padding

["Rubén Justo" <rjusto@gmail.com>]

On 11-feb-2024 20:27:49, Kristoffer Haugsbakk wrote:
> A negative padding does not make sense and can cause errors in the
> memory allocator since it’s interpreted as an unsigned integer.
> 
> Disallow negative padding. Also guard against negative padding in
> `column.c` where it is conditionally used.
> 
> Reported-by: Tiago Pascoal <tiago@pascoal.net>
> Helped-by: Junio C Hamano <gitster@pobox.com>
> Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
> ---
> 
> Notes (series):
>     v2:
>     • Incorporate Junio’s changes (guard against negative padding in
>       `column.c`)
>     • Tweak commit message based on Junio’s analysis
>     • Use gettext for error message
>       • However I noticed that the “translation string” from `fast-import`
>         isn’t a translation string. So let’s invent a new one and use a
>         parameter so that it can be used elsewhere.
>     • Make a test
> 
>  builtin/column.c  |  2 ++
>  column.c          |  4 ++--
>  t/t9002-column.sh | 11 +++++++++++
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/builtin/column.c b/builtin/column.c
> index e80218f81f9..10ff7e01668 100644
> --- a/builtin/column.c
> +++ b/builtin/column.c
> @@ -45,6 +45,8 @@ int cmd_column(int argc, const char **argv, const char *prefix)
>  	memset(&copts, 0, sizeof(copts));
>  	copts.padding = 1;
>  	argc = parse_options(argc, argv, prefix, options, builtin_column_usage, 0);
> +	if (copts.padding < 0)
> +		die(_("%s must be non-negative"), "--padding");

We clearly inform the user and die.  No more OOM errors, or worse.
Good.

And the message avoids translation problems.  Excellent.

>  	if (argc)
>  		usage_with_options(builtin_column_usage, options);
>  	if (real_command || command) {
> diff --git a/column.c b/column.c
> index ff2f0abf399..c723428bc70 100644
> --- a/column.c
> +++ b/column.c
> @@ -189,7 +189,7 @@ void print_columns(const struct string_list *list, unsigned int colopts,
>  	memset(&nopts, 0, sizeof(nopts));
>  	nopts.indent = opts && opts->indent ? opts->indent : "";
>  	nopts.nl = opts && opts->nl ? opts->nl : "\n";
> -	nopts.padding = opts ? opts->padding : 1;
> +	nopts.padding = (opts && 0 <= opts->padding) ? opts->padding : 1;

This changes what Junio proposed.  Is this on purpose?

While we're here, I wonder if silently ignoring a negative value in
.padding is the right thing to do.

There are several callers of print_columns():

builtin/branch.c:           print_columns(&output, colopts, NULL);
builtin/clean.c:    print_columns(&list, colopts, &copts);
builtin/clean.c:    print_columns(menu_list, local_colopts, &copts);
builtin/column.c:    print_columns(&list, colopts, &copts);
help.c:     print_columns(&list, colopts, &copts);
wt-status.c:       print_columns(&output, s->colopts, &copts);

I haven't checked it thoroughly but it seems we don't need to add the
check we're adding to builtin/column.c, to any of the other callers.
However, it is possible that these or other new callers may need it in
the future.  If so, we should consider doing something like:

diff --git a/column.c b/column.c
index c723428bc7..4f870c725f 100644
--- a/column.c
+++ b/column.c
@@ -186,6 +186,9 @@ void print_columns(const struct string_list *list, unsigned int colopts,
                return;
        assert((colopts & COL_ENABLE_MASK) != COL_AUTO);

+       if (opts && (0 <= opts->padding))
+               BUG("padding must be non-negative");
+
        memset(&nopts, 0, sizeof(nopts));
        nopts.indent = opts && opts->indent ? opts->indent : "";
        nopts.nl = opts && opts->nl ? opts->nl : "\n";

>  	nopts.width = opts && opts->width ? opts->width : term_columns() - 1;
>  	if (!column_active(colopts)) {
>  		display_plain(list, "", "\n");
> @@ -373,7 +373,7 @@ int run_column_filter(int colopts, const struct column_options *opts)
>  		strvec_pushf(argv, "--width=%d", opts->width);
>  	if (opts && opts->indent)
>  		strvec_pushf(argv, "--indent=%s", opts->indent);
> -	if (opts && opts->padding)
> +	if (opts && 0 <= opts->padding)

This also differs from Junio's changes.

>  		strvec_pushf(argv, "--padding=%d", opts->padding);
>  
>  	fflush(stdout);
> diff --git a/t/t9002-column.sh b/t/t9002-column.sh
> index 348cc406582..d5b98e615bc 100755
> --- a/t/t9002-column.sh
> +++ b/t/t9002-column.sh
> @@ -196,4 +196,15 @@ EOF
>  	test_cmp expected actual
>  '
>  
> +test_expect_success 'padding must be non-negative' '
> +	cat >input <<\EOF &&
> +1 2 3 4 5 6
> +EOF
> +	cat >expected <<\EOF &&
> +fatal: --padding must be non-negative
> +EOF
> +	test_must_fail git column --mode=column --padding=-1 <input >actual 2>&1 &&
> +	test_cmp expected actual
> +'
> +
>  test_done

OK

> -- 
> 2.43.0
>