[git commit] nsenter,unshare: share common code; fix a bug of not closing all fds
Denys Vlasenko
vda.linux at googlemail.com
Sat Apr 2 16:06:24 UTC 2016
commit: https://git.busybox.net/busybox/commit/?id=8220399173cf8d25e37059cadac96ac30f94e82a
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master
function old new delta
xvfork_parent_waits_and_exits - 64 +64
exec_prog_or_SHELL - 39 +39
unshare_main 873 810 -63
nsenter_main 663 596 -67
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/2 up/down: 106/-130) Total: -27 bytes
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
include/libbb.h | 6 ++++--
libbb/executable.c | 11 ++++++++++-
libbb/xfuncs_printf.c | 16 ++++++++++++++++
util-linux/nsenter.c | 21 +++++----------------
util-linux/unshare.c | 19 +++----------------
5 files changed, 38 insertions(+), 35 deletions(-)
diff --git a/include/libbb.h b/include/libbb.h
index 5b4280e..64e61cd 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -992,9 +992,10 @@ int BB_EXECVP(const char *file, char *const argv[]) FAST_FUNC;
#define BB_EXECVP(prog,cmd) execvp(prog,cmd)
#define BB_EXECLP(prog,cmd,...) execlp(prog,cmd,__VA_ARGS__)
#endif
-int BB_EXECVP_or_die(char **argv) NORETURN FAST_FUNC;
+void BB_EXECVP_or_die(char **argv) NORETURN FAST_FUNC;
+void exec_prog_or_SHELL(char **argv) NORETURN FAST_FUNC;
-/* xvfork() can't be a _function_, return after vfork mangles stack
+/* xvfork() can't be a _function_, return after vfork in child mangles stack
* in the parent. It must be a macro. */
#define xvfork() \
({ \
@@ -1006,6 +1007,7 @@ int BB_EXECVP_or_die(char **argv) NORETURN FAST_FUNC;
#if BB_MMU
pid_t xfork(void) FAST_FUNC;
#endif
+void xvfork_parent_waits_and_exits(void) FAST_FUNC;
/* NOMMU friendy fork+exec: */
pid_t spawn(char **argv) FAST_FUNC;
diff --git a/libbb/executable.c b/libbb/executable.c
index 85ecc3e..05e7031 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -83,10 +83,19 @@ int FAST_FUNC BB_EXECVP(const char *file, char *const argv[])
}
#endif
-int FAST_FUNC BB_EXECVP_or_die(char **argv)
+void FAST_FUNC BB_EXECVP_or_die(char **argv)
{
BB_EXECVP(argv[0], argv);
/* SUSv3-mandated exit codes */
xfunc_error_retval = (errno == ENOENT) ? 127 : 126;
bb_perror_msg_and_die("can't execute '%s'", argv[0]);
}
+
+/* Typical idiom for applets which exec *optional* PROG [ARGS] */
+void FAST_FUNC exec_prog_or_SHELL(char **argv)
+{
+ if (argv[0]) {
+ BB_EXECVP_or_die(argv);
+ }
+ run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
+}
diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index 4aa1b5c..e9222f6 100644
--- a/libbb/xfuncs_printf.c
+++ b/libbb/xfuncs_printf.c
@@ -659,3 +659,19 @@ pid_t FAST_FUNC xfork(void)
return pid;
}
#endif
+
+void FAST_FUNC xvfork_parent_waits_and_exits(void)
+{
+ pid_t pid;
+
+ fflush_all();
+ pid = xvfork();
+ if (pid > 0) {
+ /* Parent */
+ int exit_status = wait_for_exitstatus(pid);
+ if (WIFSIGNALED(exit_status))
+ kill_myself_with_sig(WTERMSIG(exit_status));
+ _exit(WEXITSTATUS(exit_status));
+ }
+ /* Child continues */
+}
diff --git a/util-linux/nsenter.c b/util-linux/nsenter.c
index 9c1daba..0dad595 100644
--- a/util-linux/nsenter.c
+++ b/util-linux/nsenter.c
@@ -230,7 +230,7 @@ int nsenter_main(int argc UNUSED_PARAM, char **argv)
ns->ns_nsfile8 + 3 /* skip over "ns/" */
);
}
- /*close(ns_ctx->fd);*/
+ close(ns_ctx->fd); /* should close fds, to not confuse exec'ed PROG */
/*ns_ctx->fd = -1;*/
}
@@ -244,13 +244,13 @@ int nsenter_main(int argc UNUSED_PARAM, char **argv)
}
xfchdir(root_fd);
xchroot(".");
- /*close(root_fd);*/
+ close(root_fd);
/*root_fd = -1;*/
}
if (wd_fd >= 0) {
xfchdir(wd_fd);
- /*close(wd_fd);*/
+ close(wd_fd);
/*wd_fd = -1;*/
}
@@ -259,14 +259,7 @@ int nsenter_main(int argc UNUSED_PARAM, char **argv)
* explicitly requested by the user not to.
*/
if (!(opts & OPT_nofork) && (opts & OPT_pid)) {
- pid_t pid = xvfork();
- if (pid > 0) {
- /* Parent */
- int exit_status = wait_for_exitstatus(pid);
- if (WIFSIGNALED(exit_status))
- kill_myself_with_sig(WTERMSIG(exit_status));
- return WEXITSTATUS(exit_status);
- }
+ xvfork_parent_waits_and_exits();
/* Child continues */
}
@@ -278,9 +271,5 @@ int nsenter_main(int argc UNUSED_PARAM, char **argv)
if (opts & OPT_setuid)
xsetuid(uid);
- if (*argv) {
- BB_EXECVP_or_die(argv);
- }
-
- run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
+ exec_prog_or_SHELL(argv);
}
diff --git a/util-linux/unshare.c b/util-linux/unshare.c
index 2a5bea5..95a7cb6 100644
--- a/util-linux/unshare.c
+++ b/util-linux/unshare.c
@@ -281,7 +281,7 @@ int unshare_main(int argc UNUSED_PARAM, char **argv)
if (fdp.wr >= 0) {
close(fdp.wr); /* Release child */
- /*close(fdp.rd);*/
+ close(fdp.rd); /* should close fd, to not confuse exec'ed PROG */
}
if (need_mount) {
@@ -307,14 +307,7 @@ int unshare_main(int argc UNUSED_PARAM, char **argv)
* that'll become PID 1 in this new namespace.
*/
if (opts & OPT_fork) {
- pid_t pid = xfork();
- if (pid > 0) {
- /* Parent */
- int exit_status = wait_for_exitstatus(pid);
- if (WIFSIGNALED(exit_status))
- kill_myself_with_sig(WTERMSIG(exit_status));
- return WEXITSTATUS(exit_status);
- }
+ xvfork_parent_waits_and_exits();
/* Child continues */
}
@@ -354,11 +347,5 @@ int unshare_main(int argc UNUSED_PARAM, char **argv)
mount_or_die("proc", proc_mnt_target, "proc", MS_NOSUID | MS_NOEXEC | MS_NODEV);
}
- if (argv[0]) {
- BB_EXECVP_or_die(argv);
- }
- /* unshare from util-linux 2.27.1, despite not documenting it,
- * runs a login shell (argv0="-sh") if no PROG is given
- */
- run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
+ exec_prog_or_SHELL(argv);
}
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