Subject: Re: [PATCH] rev-parse: Detect missing opt-spec

From: SZEDER Gábor <[email-masked]>
Date: Fri, 2 Sep 2022 08:47:27 +0200

On Fri, Sep 02, 2022 at 07:06:21AM +0200, Øystein Walle wrote:
> If a line in parseopts's input starts with one of the flag characters it
> is erroneously parsed as a opt-spec where the short name of the option
> is the flag character itself and the long name is after the end of the
> string. This makes Git want to allocate SIZE_MAX bytes of memory at this
> line:
> 
>     o->long_name = xmemdupz(sb.buf + 2, s - sb.buf - 2);
> 
> Since s and sb.buf are equal the second argument is -2 (except unsigned)
> and xmemdupz allocates len + 1 bytes, ie. -1 meaning SIZE_MAX.

I suspect (but didn't actually check) that this bug was added in
2d893dff4c (rev-parse --parseopt: allow [*=?!] in argument hints,
2015-07-14).

> Avoid this by checking whether a flag character was found in the zeroth
> position.
> 
> Signed-off-by: Øystein Walle <[email-masked]>
> ---
>  builtin/rev-parse.c           | 3 +++
>  t/t1502-rev-parse-parseopt.sh | 9 +++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
> index b259d8990a..04958cf9a9 100644
> --- a/builtin/rev-parse.c
> +++ b/builtin/rev-parse.c
> @@ -479,6 +479,9 @@ static int cmd_parseopt(int argc, const char **argv, const char *prefix)
>  		if (!s)
>  			s = help;
>  
> +		if (s == sb.buf)
> +			die(_("Missing opt-spec before option flags"));
> +
>  		if (s - sb.buf == 1) /* short option only */
>  			o->short_name = *sb.buf;
>  		else if (sb.buf[1] != ',') /* long option only */
> diff --git a/t/t1502-rev-parse-parseopt.sh b/t/t1502-rev-parse-parseopt.sh
> index 284fe18e72..15bc240027 100755
> --- a/t/t1502-rev-parse-parseopt.sh
> +++ b/t/t1502-rev-parse-parseopt.sh
> @@ -306,6 +306,13 @@ test_expect_success 'test --parseopt help output: "wrapped" options normal "or:"
>  	test_cmp expect actual
>  '
>  
> +test_expect_success 'test --parseopt invalid opt-spec' '
> +	test_write_lines x -- "=, x" >spec &&
> +	echo "fatal: Missing opt-spec before option flags" >expect &&
> +	test_must_fail git rev-parse --parseopt -- >out <spec >actual 2>&1 &&

When checking an error message please don't look for it on standard
output; i.e. the redirection at the end should be '2>actual', or
perheps even better '2>err'.

> +	test_cmp expect actual
> +'
> +
>  test_expect_success 'test --parseopt help output: multi-line blurb after empty line' '
>  	sed -e "s/^|//" >spec <<-\EOF &&
>  	|cmd [--some-option]
> @@ -337,3 +344,5 @@ test_expect_success 'test --parseopt help output: multi-line blurb after empty l
>  '
>  
>  test_done
> +
> +test_done
> -- 
> 2.34.1
>