[PATCH] config.c: NULL check when reading protected config

["Glen Choo via GitGitGadget" <gitgitgadget@gmail.com>]

From: Glen Choo <chooglen@google.com>

In read_protected_config(), check whether each file name is NULL before
attempting to read it. This mirrors do_git_config_sequence() (which
read_protected_config() is modelled after).

Without these NULL checks,

 make SANITIZE=address test T=t0410*.sh

fails because xdg_config is NULL, causing us to call fopen(NULL).

Reported-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Glen Choo <chooglen@google.com>
---
    config.c: NULL check when reading protected config
    
    This fixes the SANITIZE=address failure on master, That was introduced
    by gc/bare-repo-discovery. Thanks again to Ævar for the original report
    [1] and for proposing a way to catch this in CI [2].
    
    [1]
    https://lore.kernel.org/git/220725.861qu9oxl4.gmgdl@evledraar.gmail.com
    [2]
    https://lore.kernel.org/git/patch-1.1-e48b6853dd5-20220726T110716Z-avarab@gmail.com

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1299%2Fchooglen%2Fconfig%2Ffix-sanitize-address-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1299/chooglen/config/fix-sanitize-address-v1
Pull-Request: https://github.com/git/git/pull/1299

 config.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/config.c b/config.c
index 015bec360f5..b0ba7f439a4 100644
--- a/config.c
+++ b/config.c
@@ -2645,9 +2645,12 @@ static void read_protected_config(void)
 	system_config = git_system_config();
 	git_global_config(&user_config, &xdg_config);
 
-	git_configset_add_file(&protected_config, system_config);
-	git_configset_add_file(&protected_config, xdg_config);
-	git_configset_add_file(&protected_config, user_config);
+	if (system_config)
+		git_configset_add_file(&protected_config, system_config);
+	if (xdg_config)
+		git_configset_add_file(&protected_config, xdg_config);
+	if (user_config)
+		git_configset_add_file(&protected_config, user_config);
 	git_configset_add_parameters(&protected_config);
 
 	free(system_config);

base-commit: 6a475b71f8c4ce708d69fdc9317aefbde3769e25
-- 
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