File 0024-c-r-use-proc-self-tid-children-instead-of-... of Package lxc

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File 0024-c-r-use-proc-self-tid-children-instead-of-pidfile.patch of Package lxc (Revision 28c7b36c8c503610cb884facc5552cf0)

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From 9bec7ccd65d53936ef41e5d2ffc0a6e9f6c1df7c Mon Sep 17 00:00:00 2001
From: Tycho Andersen <tycho.andersen@canonical.com>
Date: Fri, 26 Aug 2016 16:07:19 +0000
Subject: [PATCH 24/27] c/r: use /proc/self/tid/children instead of pidfile

All we really needed a unique temp file for was passing the pid. Since CRIU
opened this with O_EXCL | O_CREAT, this was "safe" (users could still
overwrite it afterwards, but the monitor would immediately die since the
only valid number in there was the init process).

In any case, we can just read /proc/self/tid/children, which lists the
child process.

Closes #1150

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
---
 src/lxc/criu.c | 38 ++++++++++++++------------------------
 1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index 65998ed..76d7080 100644
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -69,7 +69,6 @@ struct criu_opts {
 	char tty_id[32]; /* the criu tty id for /dev/console, i.e. "tty[${rdev}:${dev}]" */
 
 	/* restore: the file to write the init process' pid into */
-	char *pidfile;
 	const char *cgroup_path;
 	int console_fd;
 	/* The path that is bind mounted from /dev/console, if any. We don't
@@ -176,10 +175,10 @@ static void exec_criu(struct criu_opts *opts)
 			static_args += 2;
 	} else if (strcmp(opts->action, "restore") == 0) {
 		/* --root $(lxc_mount_point) --restore-detached
-		 * --restore-sibling --pidfile $foo --cgroup-root $foo
+		 * --restore-sibling --cgroup-root $foo
 		 * --lsm-profile apparmor:whatever
 		 */
-		static_args += 10;
+		static_args += 8;
 
 		tty_info[0] = 0;
 		if (load_tty_major_minor(opts->user->directory, tty_info, sizeof(tty_info)))
@@ -330,8 +329,6 @@ static void exec_criu(struct criu_opts *opts)
 		DECLARE_ARG(opts->c->lxc_conf->rootfs.mount);
 		DECLARE_ARG("--restore-detached");
 		DECLARE_ARG("--restore-sibling");
-		DECLARE_ARG("--pidfile");
-		DECLARE_ARG(opts->pidfile);
 		DECLARE_ARG("--cgroup-root");
 		DECLARE_ARG(opts->cgroup_path);
 
@@ -604,13 +601,8 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 {
 	pid_t pid;
 	struct lxc_handler *handler;
-	int fd, status;
+	int status;
 	int pipes[2] = {-1, -1};
-	char pidfile[] = "criu_restore_XXXXXX";
-
-	fd = mkstemp(pidfile);
-	if (fd < 0)
-		goto out;
 
 	handler = lxc_init(c->name, c->lxc_conf, c->config_path);
 	if (!handler)
@@ -690,7 +682,6 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 		os.action = "restore";
 		os.user = opts;
 		os.c = c;
-		os.pidfile = pidfile;
 		os.cgroup_path = cgroup_canonical_path(handler);
 		os.console_fd = c->lxc_conf->console.slave;
 		os.criu_version = criu_version;
@@ -742,8 +733,9 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 		}
 
 		if (WIFEXITED(status)) {
+			char buf[4096];
+
 			if (WEXITSTATUS(status)) {
-				char buf[4096];
 				int n;
 
 				n = read(pipes[0], buf, sizeof(buf));
@@ -758,18 +750,21 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 				goto out_fini_handler;
 			} else {
 				int ret;
-				FILE *f = fdopen(fd, "r");
+
+				ret = snprintf(buf, sizeof(buf), "/proc/self/task/%" PRId64 "/children", syscall(__NR_gettid));
+				if (ret < 0 || ret >= sizeof(buf)) {
+					ERROR("snprintf'd too many characters: %d", ret);
+					goto out_fini_handler;
+				}
+
+				FILE *f = fopen(buf, "r");
 				if (!f) {
-					SYSERROR("couldn't read restore's init pidfile %s\n", pidfile);
+					SYSERROR("couldn't read restore's children file %s\n", buf);
 					goto out_fini_handler;
 				}
-				fd = -1;
 
 				ret = fscanf(f, "%d", (int*) &handler->pid);
 				fclose(f);
-				if (unlink(pidfile) < 0 && errno != ENOENT)
-					SYSERROR("unlinking pidfile failed");
-
 				if (ret != 1) {
 					ERROR("reading restore pid failed");
 					goto out_fini_handler;
@@ -809,8 +804,6 @@ out_fini_handler:
 		close(pipes[1]);
 
 	lxc_fini(c->name, handler);
-	if (unlink(pidfile) < 0 && errno != ENOENT)
-		SYSERROR("unlinking pidfile failed");
 
 out:
 	if (status_pipe >= 0) {
@@ -821,9 +814,6 @@ out:
 		close(status_pipe);
 	}
 
-	if (fd > 0)
-		close(fd);
-
 	exit(1);
 }
 
-- 
2.9.3

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File 0024-c-r-use-proc-self-tid-children-instead-of-pidfile.patch of Package lxc (Revision 28c7b36c8c503610cb884facc5552cf0)

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