Re: [PATCH 3/5] config: add BUG() statement instead of possible segfault
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Sep 27, 2022, 16:17 UTC
- Message-ID
- <220927.86wn9oyejm.gmgdl@evledraar.gmail.com>
- In-Reply-To
- <f277a7a429db8f54fa06dd1965d62ec491e6d84b.1664287711.git.gitgitgadget@gmail.com>
On Tue, Sep 27 2022, Derrick Stolee via GitGitGadget wrote:
Show 34 quoted lines
> From: Derrick Stolee <derrickstolee@github.com>
>
> The git_die_config() method calls git_config_get_value_multi() but
> immediately navigates to its first value without checking if the result
> is NULL or empty. Callers should only call git_die_config() if there is
> at least one value for the given 'key', but such a mistaken use might
> slip through. It would be better to show a BUG() statement than a
> possible segfault.
>
> Signed-off-by: Derrick Stolee <derrickstolee@github.com>
> ---
> config.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/config.c b/config.c
> index bf89afbdab0..0c41606c7d4 100644
> --- a/config.c
> +++ b/config.c
> @@ -2833,8 +2833,13 @@ void git_die_config(const char *key, const char *err, ...)
> va_end(params);
> }
> values = git_config_get_value_multi(key);
> - kv_info = values->items[values->nr - 1].util;
> - git_die_config_linenr(key, kv_info->filename, kv_info->linenr);
> +
> + if (values && values->nr) {
> + kv_info = values->items[values->nr - 1].util;
> + git_die_config_linenr(key, kv_info->filename, kv_info->linenr);
> + } else {
> + BUG("expected a non-empty list of values");
> + }
> }
>
> /*AFAIKT the intent of the current code on "master" is that this will only get called if the likes of git_configset_get_string() returns < 0, not if it returns > 0.
So isn't the combination of your 1/5 and this 3/5 now conflating these two conditions? See e.g. repo_config_get_string_tmp() and when it would call git_die_config().
I.e. isn't the whole point of git_die_config() to print an error message about a configuration *value* that we've parsed out of the config?
If e.g. the key itself is bad we'll get a -1, but in this case it seems we would have a BUG(), but it's not that we "expected a non-empty list of values", but that the state of the world changed between our previous configset invocation, no?