[BUG/PATCH] setup: Copy an environment variable to avoid overwrites

From: David Michael <fedora.dm0@gmail.com>
Date: Jan 5, 2013, 00:35 UTC
Message-ID: <CAEvUa7niTJVfp8_kuWs50kvhfZ59F-yAuAmeOXEduHXOq-tRFA@mail.gmail.com>

It is possible for this pointer of the GIT_DIR environment variable to survive unduplicated until further getenv calls are made. The standards allow for subsequent calls of getenv to overwrite the string located at its returned pointer, and this can result in broken git operations on certain platforms.

Signed-off-by: David Michael <fedora.dm0@gmail.com>
---

I have encountered an issue with consecutive calls to getenv overwriting earlier values. Most notably, it prevents a plain "git clone" from working.

Long story short: This value of GIT_DIR gets passed around setup.c until it reaches check_repository_format_gently. This function calls git_config_early, which eventually runs getenv("HOME"). When it returns back to check_repository_format_gently, the gitdir variable contains my home directory path. The end result is that I wind up with ~/objects/ etc. and a failed repository clone. (Simply adding a bare getenv("GIT_DIR") afterwards to reset the pointer also corrects the problem.)

Since other platforms are apparently working, yet this getenv behavior is supported by the standards, I am left wondering if this could be a symptom of something else being broken on my platform (z/OS). Can anyone more familiar with this part of git identify any condition that obviously should not be occurring?

Thanks.

 setup.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/setup.c b/setup.c
index f108c4b..64fb160 100644
--- a/setup.c
+++ b/setup.c
@@ -675,8 +675,12 @@ static const char
*setup_git_directory_gently_1(int *nongit_ok)
      * validation.
      */
     gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
-    if (gitdirenv)
-        return setup_explicit_git_dir(gitdirenv, cwd, len, nongit_ok);
+    if (gitdirenv) {
+        gitdirenv = xstrdup(gitdirenv);
+        ret = setup_explicit_git_dir(gitdirenv, cwd, len, nongit_ok);
+        free(gitdirenv);
+        return ret;
+    }

     if (env_ceiling_dirs) {
         string_list_split(&ceiling_dirs, env_ceiling_dirs, PATH_SEP, -1);
--
1.7.11.7