Subject: [PATCH 2/5] run-command: prepare argv before forking

From: Brandon Williams <[email-masked]>
Date: Mon, 10 Apr 2017 16:49:16 -0700

In order to avoid allocation between 'fork()' and 'exec()' the argv
array used in the exec call is prepared prior to forking the process.

Signed-off-by: Brandon Williams <[email-masked]>
---
 run-command.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/run-command.c b/run-command.c
index 682bc3ca5..2514b54bc 100644
--- a/run-command.c
+++ b/run-command.c
@@ -226,18 +226,6 @@ static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 }
 
 #ifndef GIT_WINDOWS_NATIVE
-static int execv_shell_cmd(const char **argv)
-{
-	struct argv_array nargv = ARGV_ARRAY_INIT;
-	prepare_shell_cmd(&nargv, argv);
-	trace_argv_printf(nargv.argv, "trace: exec:");
-	sane_execvpe(nargv.argv[0], (char **)nargv.argv, NULL);
-	argv_array_clear(&nargv);
-	return -1;
-}
-#endif
-
-#ifndef GIT_WINDOWS_NATIVE
 static int child_notifier = -1;
 
 static void notify_parent(void)
@@ -377,9 +365,20 @@ int start_command(struct child_process *cmd)
 #ifndef GIT_WINDOWS_NATIVE
 {
 	int notify_pipe[2];
+	struct argv_array argv = ARGV_ARRAY_INIT;
+
 	if (pipe(notify_pipe))
 		notify_pipe[0] = notify_pipe[1] = -1;
 
+	if (cmd->git_cmd) {
+		argv_array_push(&argv, "git");
+		argv_array_pushv(&argv, cmd->argv);
+	} else if (cmd->use_shell) {
+		prepare_shell_cmd(&argv, cmd->argv);
+	} else {
+		argv_array_pushv(&argv, cmd->argv);
+	}
+
 	cmd->pid = fork();
 	failed_errno = errno;
 	if (!cmd->pid) {
@@ -442,12 +441,9 @@ int start_command(struct child_process *cmd)
 					unsetenv(*cmd->env);
 			}
 		}
-		if (cmd->git_cmd)
-			execv_git_cmd(cmd->argv);
-		else if (cmd->use_shell)
-			execv_shell_cmd(cmd->argv);
-		else
-			sane_execvpe(cmd->argv[0], (char *const*) cmd->argv, NULL);
+
+		sane_execvpe(argv.argv[0], (char *const*) argv.argv, NULL);
+
 		if (errno == ENOENT) {
 			if (!cmd->silent_exec_failure)
 				error("cannot run %s: %s", cmd->argv[0],
@@ -480,6 +476,8 @@ int start_command(struct child_process *cmd)
 		cmd->pid = -1;
 	}
 	close(notify_pipe[0]);
+
+	argv_array_clear(&argv);
 }
 #else
 {
-- 
2.12.2.715.g7642488e1d-goog