Not doing this can be a pain for restarted software which relies
on /proc...
This builds on a patch by Serge Hallyn, but also aims to address the
future cases of hierarchical pid-ns:
1) Before mounting the new /proc, first umount the old one, which
isn't necessary anymore.
2) Perform the unshare() together with the remount of /proc, so it
will occur for every new pid-ns and not only for the first one.
Signed-off-by: Oren Laadan <orenl@xxxxxxxxxxxxxxx>
---
restart.c | 32 ++++++++++++++++++++++++++++++++
1 files changed, 32 insertions(+), 0 deletions(-)
diff --git a/restart.c b/restart.c
index f3d33de..f42b456 100644
--- a/restart.c
+++ b/restart.c
@@ -30,6 +30,7 @@
#include <asm/unistd.h>
#include <sys/syscall.h>
#include <sys/prctl.h>
+#include <sys/mount.h>
#include <linux/sched.h>
#include <linux/checkpoint.h>
@@ -273,6 +274,8 @@ int global_child_collected;
int global_send_sigint = -1;
int global_sent_sigint;
+static int ckpt_remount_proc(void);
+
static int ckpt_build_tree(struct ckpt_ctx *ctx);
static int ckpt_init_tree(struct ckpt_ctx *ctx);
static int ckpt_set_creator(struct ckpt_ctx *ctx, struct task *task);
@@ -981,11 +984,36 @@ static int ckpt_probe_child(pid_t pid, char *str)
return 0;
}
+/*
+ * Remount the /proc with a new instance: tasks that start a new
+ * pid-ns need a fresh mount of /proc to reflect their pid-ns.
+ */
+static int ckpt_remount_proc(void)
+{
+ if (unshare(CLONE_NEWNS | CLONE_FS) < 0) {
+ perror("unshare");
+ return -1;
+ }
+ if (umount2("/proc", MNT_DETACH) < 0) {
+ perror("umount -l /proc");
+ return -1;
+ }
+ if (mount("proc", "/proc", "proc", 0, NULL) < 0) {
+ perror("mount -t proc");
+ return -1;
+ }
+
+ return 0;
+}
+
#ifdef CLONE_NEWPID
static int __ckpt_coordinator(void *arg)
{
struct ckpt_ctx *ctx = (struct ckpt_ctx *) arg;
+ if (ckpt_remount_proc() < 0)
+ return -1;
+
if (!ctx->args->wait)
close(ctx->pipe_coord[0]);
@@ -1850,6 +1878,10 @@ int ckpt_fork_stub(void *data)
struct task *task = (struct task *) data;
struct ckpt_ctx *ctx = task->ctx;
+ /* tasks with new pid-ns need new /proc mount */
+ if ((task->flags & TASK_NEWPID) && ckpt_remount_proc() < 0)
+ return -1;
+
/*
* In restart into a new pid namespace (--pidns), coordinator
* is the container init, hence if it terminated permatutely
--
1.6.3.3
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