From: Tycho Andersen <tycho.andersen@canonical.com>
Date: Fri, 26 Aug 2016 20:29:45 +0000 (-0400)
Subject: c/r: write status only after trying to parse the pid
X-Git-Tag: lxc-2.1.0~337^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F1155%2Fhead;p=thirdparty%2Flxc.git

c/r: write status only after trying to parse the pid

Previously, we write a "success" status but tried to parse the pid. This
meant that we wouldn't notice a successful restore but failure to parse the
pid, which was a little strange.

We still don't know the child pid, so we will end up with a restored
process tree and a running container, but at least in this case the API
will return false indicating that something failed.

We could kill(-1, 9) in this case, but since liblxc runs as root sometimes
(e.g. LXD), that would be a Very Bad Thing.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
---

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index 5a48c7203..71c9b9c32 100644
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -723,15 +723,6 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 			goto out_fini_handler;
 		}
 
-		ret = write(status_pipe, &status, sizeof(status));
-		close(status_pipe);
-		status_pipe = -1;
-
-		if (sizeof(status) != ret) {
-			SYSERROR("failed to write all of status");
-			goto out_fini_handler;
-		}
-
 		if (WIFEXITED(status)) {
 			char buf[4096];
 
@@ -780,6 +771,15 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 
 		close(pipes[0]);
 
+		ret = write(status_pipe, &status, sizeof(status));
+		close(status_pipe);
+		status_pipe = -1;
+
+		if (sizeof(status) != ret) {
+			SYSERROR("failed to write all of status");
+			goto out_fini_handler;
+		}
+
 		/*
 		 * See comment in lxcapi_start; we don't care if these
 		 * fail because it's just a beauty thing. We just
@@ -805,7 +805,12 @@ out_fini_handler:
 
 out:
 	if (status_pipe >= 0) {
-		status = 1;
+		/* ensure getting here was a failure, e.g. if we failed to
+		 * parse the child pid or something, even after a successful
+		 * restore
+		 */
+		if (!status)
+			status = 1;
 		if (write(status_pipe, &status, sizeof(status)) != sizeof(status)) {
 			SYSERROR("writing status failed");
 		}