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

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-01-26 01:13:58 +01:00
parent 06f20bf675
commit 9967c9949e
3 changed files with 35 additions and 22 deletions
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7
docs/nofork_noexec.txt
View File

@ -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

14
include/libbb.h
View File

@ -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;

36
libbb/vfork_daemon_rexec.c
View File

@ -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 */