[PATCH v2 1/2] Clean stale environment pointer in finish_command()

In start_command(), unset "env" fields are initialized via "env_array". In
finish_command(), the "env_array" is cleared, therefore the "env" field
will point to free()d data.

However, start_command() will set "env" to env_array.argv only if "env"
was unset to begin with, and if it was already set, the caller will need
the original value. Therefore, we need to be very careful only to reset
"env" in finish_command() when it has been initialized in start_command().

Signed-off-by: Johannes Schindelin <redacted>
---
 run-command.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/run-command.c b/run-command.c
index 79a0a76..85578da 100644
--- a/run-command.c
+++ b/run-command.c

@@ -555,6 +555,9 @@ int finish_command(struct child_process *cmd)
 {
 	int ret = wait_or_whine(cmd->pid, cmd->argv[0]);
 	argv_array_clear(&cmd->args);
+	/* Avoid pointing to a stale environment */
+	if (cmd->env == cmd->env_array.argv)
+		cmd->env = NULL;
 	argv_array_clear(&cmd->env_array);
 	return ret;
 }

-- 
2.0.0.rc3.9669.g840d1f9