9967c9949

Denys Vlasenko

2017-01-26

SUCCESS Duration: 212s

Subject

libbb: spawn_and_wait() fflushes before forking NOEXEC; child reinits logmode

No binary (build failed)

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

(log yok)

docs/nofork_noexec.txt+7 -0

@@ -99,6 +99,13 @@ applet_name. Thus, for example, caller does not need to worry about
	option_mask32 getting trashed.


+	Calling NOEXEC applets
+
+	It's the same trusty spawn_and_wait(argv). If FEATURE_PREFER_APPLETS=y,
+	it does NOEXEC trick. It resets xfunc_error_retval = 1 and
+	logmode = LOGMODE_STDIO in the child.
+
+
	Relevant CONFIG options

	FEATURE_PREFER_APPLETS

include/libbb.h+9 -5

@@ -1093,10 +1093,19 @@ pid_t wait_any_nohang(int *wstat) FAST_FUNC;
	*/
	int wait4pid(pid_t pid) FAST_FUNC;
	int wait_for_exitstatus(pid_t pid) FAST_FUNC;
+	/************************************************************************/
+	/* spawn_and_wait/run_nofork_applet/run_applet_no_and_exit need to work */
+	/* carefully together to reinit some global state while not disturbing */
+	/* other. Be careful if you change them. Consult docs/nofork_noexec.txt */
+	/************************************************************************/
	/* Same as wait4pid(spawn(argv)), but with NOFORK/NOEXEC if configured: */
	int spawn_and_wait(char **argv) FAST_FUNC;
	/* Does NOT check that applet is NOFORK, just blindly runs it */
	int run_nofork_applet(int applet_no, char **argv) FAST_FUNC;
+	#ifndef BUILD_INDIVIDUAL
+	extern int find_applet_by_name(const char *name) FAST_FUNC;
+	extern void run_applet_no_and_exit(int a, char **argv) NORETURN FAST_FUNC;
+	#endif

	/* Helpers for daemonization.
	*
@@ -1303,11 +1312,6 @@ const struct hwtype get_hwtype(const char name) FAST_FUNC;
	const struct hwtype *get_hwntype(int type) FAST_FUNC;


-	#ifndef BUILD_INDIVIDUAL
-	extern int find_applet_by_name(const char *name) FAST_FUNC;
-	extern void run_applet_no_and_exit(int a, char **argv) NORETURN FAST_FUNC;
-	#endif
-
	#ifdef HAVE_MNTENT_H
	extern int match_fstype(const struct mntent mt, const char fstypes) FAST_FUNC;
	extern struct mntent find_mount_point(const char name, int subdir_too) FAST_FUNC;

libbb/vfork_daemon_rexec.c+19 -17

@@ -183,26 +183,28 @@ int FAST_FUNC spawn_and_wait(char **argv)
	#if ENABLE_FEATURE_PREFER_APPLETS
	int a = find_applet_by_name(argv[0]);

-	if (a >= 0 && (APPLET_IS_NOFORK(a)
-	# if BB_MMU
-	\|\| APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
-	# endif
-	)) {
-	# if BB_MMU
+	if (a >= 0) {
	if (APPLET_IS_NOFORK(a))
-	# endif
-	{
	return run_nofork_applet(a, argv);
+	# if BB_MMU /* NOEXEC needs fork(), thus this is done only on MMU machines: */
+	if (APPLET_IS_NOEXEC(a)) {
+	fflush_all();
+	rc = fork();
+	if (rc) /* parent or error */
+	return wait4pid(rc);
+
+	/* child */
+	/* reset some state and run without execing */
+
+	/* msg_eol = "\n"; - no caller needs this reinited yet */
+	logmode = LOGMODE_STDIO;
+	/* die_func = NULL; - needed if the caller is a shell,
+	* init, or a NOFORK applet. But none of those call us
+	* as of yet (and that should probably always stay true).
+	*/
+	/* xfunc_error_retval and applet_name are init by: */
+	run_applet_no_and_exit(a, argv);
	}
-	# if BB_MMU
-	/* MMU only */
-	/* a->noexec is true */
-	rc = fork();
-	if (rc) /* parent or error */
-	return wait4pid(rc);
-	/* child */
-	xfunc_error_retval = EXIT_FAILURE;
-	run_applet_no_and_exit(a, argv);
	# endif
	}
	#endif /* FEATURE_PREFER_APPLETS */