Re: [PATCHv3 1/4] notes: don't leak memory in git_config_get_notes_strategy

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Mar 31, 2016, 21:08 UTC
Message-ID: <CAPig+cRPNt1aNdsONXgX0SkgNiYtTS8vCGQzE2u4+vpd-N-Vew@mail.gmail.com>
In-Reply-To: <1459447446-32260-2-git-send-email-sbeller@google.com>

On Thu, Mar 31, 2016 at 2:04 PM, Stefan Beller <sbeller@google.com> wrote:

Show 16 quoted lines

> `value` is just a temporary scratchpad, so we need to make sure it doesn't
> leak. It is xstrdup'd in `git_config_get_string_const` and
> `parse_notes_merge_strategy` just compares the string against predefined
> values, so no need to keep it around longer. Instead of using
> `git_config_get_string_const`, use `git_config_get_value`, which doesn't
> return a copy.
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
> diff --git a/builtin/notes.c b/builtin/notes.c
> @@ -746,7 +746,7 @@ static int git_config_get_notes_strategy(const char *key,
>  {
>         const char *value;
>
> -       if (git_config_get_string_const(key, &value))
> +       if (git_config_get_value(key, &value))

Hmm, doesn't this introduce a rather severe regression? Unless I'm misreading the code (possible), with the original, if 'key' was boolean (lacked a value in the config file), then it would complain:

    Missing value for 'floop.blork'

but, with this change, it will dereference NULL and crash.

(My understanding was that Peff's suggestion to use git_config_get_value() implied a bit of work beyond the simple textual substitution of 'git_config_get_value' for 'git_config_get_string_const'.)

>                 return 1;
>         if (parse_notes_merge_strategy(value, strategy))
>                 git_die_config(key, "unknown notes merge strategy %s", value);