Subject: Re: [PATCH v2] rev-parse: Check argc before using argv[i+1]

From: Junio C Hamano <[email-masked]>
Date: Tue, 28 Jan 2014 13:43:56 -0800

David Sharp <[email-masked]> writes:

> Without this patch, git-rev-parse --prefix, --default, or
> --resolve-git-dir, without a value argument, would result in a segfault.
> Instead, die() with a message.

When I sent the review message, I actually was on the fence between
checking i vs argc and checking the nullness myself.  I realize,
after seeing the actual patch below, that we are protecting against
picking up a NULL and blindly passing it on in the codepaths that
follow, so the updated code does look a lot better, at least to me.

Thanks.

>
> Signed-off-by: David Sharp <[email-masked]>
> ---
>  builtin/rev-parse.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
> index aaeb611..45901df 100644
> --- a/builtin/rev-parse.c
> +++ b/builtin/rev-parse.c
> @@ -547,15 +547,17 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
>  				continue;
>  			}
>  			if (!strcmp(arg, "--default")) {
> -				def = argv[i+1];
> -				i++;
> +				def = argv[++i];
> +				if (!def)
> +					die("--default requires an argument");
>  				continue;
>  			}
>  			if (!strcmp(arg, "--prefix")) {
> -				prefix = argv[i+1];
> +				prefix = argv[++i];
> +				if (!prefix)
> +					die("--prefix requires an argument");
>  				startup_info->prefix = prefix;
>  				output_prefix = 1;
> -				i++;
>  				continue;
>  			}
>  			if (!strcmp(arg, "--revs-only")) {
> @@ -738,9 +740,12 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
>  				continue;
>  			}
>  			if (!strcmp(arg, "--resolve-git-dir")) {
> -				const char *gitdir = resolve_gitdir(argv[i+1]);
> +				const char *gitdir = argv[++i];
>  				if (!gitdir)
> -					die("not a gitdir '%s'", argv[i+1]);
> +					die("--resolve-git-dir requires an argument");
> +				gitdir = resolve_gitdir(gitdir);
> +				if (!gitdir)
> +					die("not a gitdir '%s'", argv[i]);
>  				puts(gitdir);
>  				continue;
>  			}