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Subject[RFC v16][PATCH 28/43] c/r: make ckpt_may_checkpoint_task() check each namespace individually
Date
From: Dan Smith <danms@us.ibm.com>

Signed-off-by: Dan Smith <danms@us.ibm.com>
Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
checkpoint/checkpoint.c | 20 ++++++--
checkpoint/objhash.c | 28 +++++++++++
checkpoint/process.c | 101 ++++++++++++++++++++++++++++++++++++++++
include/linux/checkpoint.h | 4 ++
include/linux/checkpoint_hdr.h | 8 +++
5 files changed, 157 insertions(+), 4 deletions(-)

diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index b70adf4..e66f82b 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -267,6 +267,8 @@ static int checkpoint_all_tasks(struct ckpt_ctx *ctx)
static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t)
{
struct task_struct *root = ctx->root_task;
+ struct nsproxy *nsproxy;
+ int ret = 0;

ckpt_debug("check %d\n", task_pid_nr_ns(t, ctx->root_nsproxy->pid_ns));

@@ -306,11 +308,21 @@ static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t)
return -EINVAL;
}

- /* FIX: change this when namespaces are added */
- if (task_nsproxy(t) != ctx->root_nsproxy)
- return -EPERM;
+ rcu_read_lock();
+ nsproxy = task_nsproxy(t);
+ if (nsproxy->uts_ns != ctx->root_nsproxy->uts_ns)
+ ret = -EPERM;
+ if (nsproxy->ipc_ns != ctx->root_nsproxy->ipc_ns)
+ ret = -EPERM;
+ if (nsproxy->mnt_ns != ctx->root_nsproxy->mnt_ns)
+ ret = -EPERM;
+ if (nsproxy->pid_ns != ctx->root_nsproxy->pid_ns)
+ ret = -EPERM;
+ if (nsproxy->net_ns != ctx->root_nsproxy->net_ns)
+ ret = -EPERM;
+ rcu_read_unlock();

- return 0;
+ return ret;
}

#define CKPT_HDR_PIDS_CHUNK 256
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index e481911..56553ae 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -127,6 +127,22 @@ static int obj_mm_users(void *ptr)
return atomic_read(&((struct mm_struct *) ptr)->mm_users);
}

+static int obj_ns_grab(void *ptr)
+{
+ get_nsproxy((struct nsproxy *) ptr);
+ return 0;
+}
+
+static void obj_ns_drop(void *ptr)
+{
+ put_nsproxy((struct nsproxy *) ptr);
+}
+
+static int obj_ns_users(void *ptr)
+{
+ return atomic_read(&((struct nsproxy *) ptr)->count);
+}
+
static struct ckpt_obj_ops ckpt_obj_ops[] = {
/* ignored object */
{
@@ -174,6 +190,16 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.checkpoint = checkpoint_mm,
.restore = restore_mm,
},
+ /* ns object */
+ {
+ .obj_name = "NSPROXY",
+ .obj_type = CKPT_OBJ_NS,
+ .ref_drop = obj_ns_drop,
+ .ref_grab = obj_ns_grab,
+ .ref_users = obj_ns_users,
+ .checkpoint = checkpoint_ns,
+ .restore = restore_ns,
+ },
};


@@ -396,6 +422,8 @@ int ckpt_obj_contained(struct ckpt_ctx *ctx)

/* account for ctx->file reference (if in the table already) */
ckpt_obj_users_inc(ctx, ctx->file, 1);
+ /* account for ctx->root_nsproxy reference (if in the table already) */
+ ckpt_obj_users_inc(ctx, ctx->root_nsproxy, 1);

hlist_for_each_entry(obj, node, &ctx->obj_hash->list, next) {
if (!obj->ops->ref_users)
diff --git a/checkpoint/process.c b/checkpoint/process.c
index 876be3e..fbe0d16 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -12,6 +12,7 @@
#define CKPT_DFLAG CKPT_DSYS

#include <linux/sched.h>
+#include <linux/nsproxy.h>
#include <linux/posix-timers.h>
#include <linux/futex.h>
#include <linux/poll.h>
@@ -49,6 +50,45 @@ static int checkpoint_task_struct(struct ckpt_ctx *ctx, struct task_struct *t)
return ckpt_write_string(ctx, t->comm, TASK_COMM_LEN);
}

+
+static int do_checkpoint_ns(struct ckpt_ctx *ctx, struct nsproxy *nsproxy)
+{
+ return 0;
+}
+
+int checkpoint_ns(struct ckpt_ctx *ctx, void *ptr)
+{
+ return do_checkpoint_ns(ctx, (struct nsproxy *) ptr);
+}
+
+static int checkpoint_task_ns(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct ckpt_hdr_task_ns *h;
+ struct nsproxy *nsproxy;
+ int ns_objref;
+ int ret;
+
+ rcu_read_lock();
+ nsproxy = task_nsproxy(t);
+ get_nsproxy(nsproxy);
+ rcu_read_unlock();
+
+ ns_objref = checkpoint_obj(ctx, nsproxy, CKPT_OBJ_NS);
+ put_nsproxy(nsproxy);
+
+ ckpt_debug("nsproxy: objref %d\n", ns_objref);
+ if (ns_objref < 0)
+ return ns_objref;
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_TASK_NS);
+ if (!h)
+ return -ENOMEM;
+ h->ns_objref = ns_objref;
+ ret = ckpt_write_obj(ctx, &h->h);
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
{
struct ckpt_hdr_task_objs *h;
@@ -56,6 +96,18 @@ static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
int mm_objref;
int ret;

+ /*
+ * Shared objects may have dependencies among them: task->mm
+ * depends on task->nsproxy (by ipc_ns). Therefore first save
+ * the namespaces, and then the remaining shared objects.
+ * During restart a task will already have its namespaces
+ * restored when it gets to restore, e.g. its memory.
+ */
+
+ ret = checkpoint_task_ns(ctx, t);
+ if (ret < 0)
+ return ret;
+
files_objref = checkpoint_obj_file_table(ctx, t);
ckpt_debug("files: objref %d\n", files_objref);
if (files_objref < 0) {
@@ -248,11 +300,60 @@ static int restore_task_struct(struct ckpt_ctx *ctx)
return ret;
}

+static struct nsproxy *do_restore_ns(struct ckpt_ctx *ctx)
+{
+ struct nsproxy *nsproxy;
+
+ nsproxy = task_nsproxy(current);
+ get_nsproxy(nsproxy);
+ return nsproxy;
+}
+
+void *restore_ns(struct ckpt_ctx *ctx)
+{
+ return (void *) do_restore_ns(ctx);
+}
+
+static int restore_task_ns(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_task_ns *h;
+ struct nsproxy *nsproxy;
+ int ret = 0;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_TASK_NS);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ nsproxy = ckpt_obj_fetch(ctx, h->ns_objref, CKPT_OBJ_NS);
+ if (IS_ERR(nsproxy)) {
+ ret = PTR_ERR(nsproxy);
+ goto out;
+ }
+
+ if (nsproxy != task_nsproxy(current)) {
+ get_nsproxy(nsproxy);
+ switch_task_namespaces(current, nsproxy);
+ }
+ out:
+ ckpt_debug("nsproxy: ret %d (%p)\n", ret, task_nsproxy(current));
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
static int restore_task_objs(struct ckpt_ctx *ctx)
{
struct ckpt_hdr_task_objs *h;
int ret;

+ /*
+ * Namespaces come first, because ->mm depends on ->nsproxy,
+ * and because shared objects are restored before they are
+ * referenced. See comment in checkpoint_task_objs.
+ */
+ ret = restore_task_ns(ctx);
+ if (ret < 0)
+ return ret;
+
h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_TASK_OBJS);
if (IS_ERR(h))
return PTR_ERR(h);
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 171e92e..a7125fc 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -77,6 +77,10 @@ extern int checkpoint_restart_block(struct ckpt_ctx *ctx,
struct task_struct *t);
extern int restore_restart_block(struct ckpt_ctx *ctx);

+/* namespaces */
+extern int checkpoint_ns(struct ckpt_ctx *ctx, void *ptr);
+extern void *restore_ns(struct ckpt_ctx *ctx);
+
/* file table */
extern int checkpoint_obj_file_table(struct ckpt_ctx *ctx,
struct task_struct *t);
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 14654e8..da1ae79 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -48,6 +48,7 @@ enum {

CKPT_HDR_TREE = 101,
CKPT_HDR_TASK,
+ CKPT_HDR_TASK_NS,
CKPT_HDR_TASK_OBJS,
CKPT_HDR_RESTART_BLOCK,
CKPT_HDR_THREAD,
@@ -90,6 +91,7 @@ enum obj_type {
CKPT_OBJ_FILE_TABLE,
CKPT_OBJ_FILE,
CKPT_OBJ_MM,
+ CKPT_OBJ_NS,
CKPT_OBJ_MAX
};

@@ -152,6 +154,12 @@ struct ckpt_hdr_task {
__u32 task_comm_len;
} __attribute__((aligned(8)));

+/* namespaces */
+struct ckpt_hdr_task_ns {
+ struct ckpt_hdr h;
+ __s32 ns_objref;
+} __attribute__((aligned(8)));
+
/* task's shared resources */
struct ckpt_hdr_task_objs {
struct ckpt_hdr h;
--
1.6.0.4


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