run-command: prepare command before forking
According to [1] we need to only call async-signal-safe operations between fork and exec. Using malloc to build the argv array isn't async-signal-safe. In order to avoid allocation between 'fork()' and 'exec()' prepare the argv array used in the exec call prior to forking the process. [1] http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html Signed-off-by: Brandon Williams <bmwill@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Brandon Williams committed
Apr 19, 2017 at 16:13 UTC
3967e25be11ab96ced71f16b9f082de270a518db
1 file changed
+26
-20
run-command.c
+26
-20
@@ -220,18 +220,6 @@ static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
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return out->argv;
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}
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-#ifndef GIT_WINDOWS_NATIVE
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-static int execv_shell_cmd(const char **argv)
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-{
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- struct argv_array nargv = ARGV_ARRAY_INIT;
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- prepare_shell_cmd(&nargv, argv);
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- trace_argv_printf(nargv.argv, "trace: exec:");
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- sane_execvp(nargv.argv[0], (char **)nargv.argv);
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- argv_array_clear(&nargv);
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- return -1;
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-}
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-#endif
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-
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#ifndef GIT_WINDOWS_NATIVE
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static int child_notifier = -1;
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@@ -244,6 +232,21 @@ static void notify_parent(void)
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*/
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xwrite(child_notifier, "", 1);
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}
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+
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+static void prepare_cmd(struct argv_array *out, const struct child_process *cmd)
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+{
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+ if (!cmd->argv[0])
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+ die("BUG: command is empty");
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+
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+ if (cmd->git_cmd) {
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+ argv_array_push(out, "git");
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+ argv_array_pushv(out, cmd->argv);
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+ } else if (cmd->use_shell) {
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+ prepare_shell_cmd(out, cmd->argv);
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+ } else {
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+ argv_array_pushv(out, cmd->argv);
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+ }
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+}
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#endif
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static inline void set_cloexec(int fd)
@@ -372,9 +375,13 @@ fail_pipe:
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#ifndef GIT_WINDOWS_NATIVE
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{
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int notify_pipe[2];
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+ struct argv_array argv = ARGV_ARRAY_INIT;
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+
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if (pipe(notify_pipe))
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notify_pipe[0] = notify_pipe[1] = -1;
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+ prepare_cmd(&argv, cmd);
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+
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cmd->pid = fork();
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failed_errno = errno;
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if (!cmd->pid) {
@@ -437,12 +444,9 @@ fail_pipe:
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unsetenv(*cmd->env);
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}
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}
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- if (cmd->git_cmd)
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- execv_git_cmd(cmd->argv);
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- else if (cmd->use_shell)
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- execv_shell_cmd(cmd->argv);
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- else
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- sane_execvp(cmd->argv[0], (char *const*) cmd->argv);
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+
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+ sane_execvp(argv.argv[0], (char *const *) argv.argv);
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+
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if (errno == ENOENT) {
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if (!cmd->silent_exec_failure)
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error("cannot run %s: %s", cmd->argv[0],
@@ -458,7 +462,7 @@ fail_pipe:
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mark_child_for_cleanup(cmd->pid, cmd);
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/*
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- * Wait for child's execvp. If the execvp succeeds (or if fork()
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+ * Wait for child's exec. If the exec succeeds (or if fork()
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* failed), EOF is seen immediately by the parent. Otherwise, the
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* child process sends a single byte.
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* Note that use of this infrastructure is completely advisory,
@@ -467,7 +471,7 @@ fail_pipe:
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close(notify_pipe[1]);
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if (read(notify_pipe[0], ¬ify_pipe[1], 1) == 1) {
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/*
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- * At this point we know that fork() succeeded, but execvp()
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+ * At this point we know that fork() succeeded, but exec()
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* failed. Errors have been reported to our stderr.
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*/
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wait_or_whine(cmd->pid, cmd->argv[0], 0);
@@ -475,6 +479,8 @@ fail_pipe:
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cmd->pid = -1;
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}
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close(notify_pipe[0]);
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+
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+ argv_array_clear(&argv);
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}
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#else
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{