kernel: Drop no longer needed CLONE_CHILD_USEPID functionality

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

kernel/clone-Introduce-the-CLONE_CHILD_USEPID-functionality

-clone: Introduce the CLONE_CHILD_USEPID functionality
-
-From: Pavel Emelyanov <xemul@openvz.org>
-
-When restoring a task (or a set of tasks) we need to recreate them with
-exactly the same pid as they had before. Thus we need the ability to create
-a task with specified pid.
-
-The proposal is to reuse the already free CLONE_STOPPED clone flag.
-
-About the security implication - this can create some problems with pids
-wraparound and similar, so this approach can be restricted with the "don't
-allow for CLONE_CHILD_USEPID when the current pid namespace has ever done
-real pid allocation". This will work perfectly for checkpoint-restore and
-will not give anyone chances for screwing pids up on a living system.
-
-Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
----
- include/linux/pid.h   |    2 -
- include/linux/sched.h |    1 
- kernel/fork.c         |   10 ++++++-
- kernel/pid.c          |   70 ++++++++++++++++++++++++++++++++++++--------------
- 4 files changed, 62 insertions(+), 21 deletions(-)
-
-Index: linux-2.6.git/include/linux/pid.h
-===================================================================
---- linux-2.6.git.orig/include/linux/pid.h
-+++ linux-2.6.git/include/linux/pid.h
-@@ -119,7 +119,7 @@ extern struct pid *find_get_pid(int nr);
- extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
- int next_pidmap(struct pid_namespace *pid_ns, unsigned int last);
- 
--extern struct pid *alloc_pid(struct pid_namespace *ns);
-+extern struct pid *alloc_pid(struct pid_namespace *ns, int pid);
- extern void free_pid(struct pid *pid);
- 
- /*
-Index: linux-2.6.git/include/linux/sched.h
-===================================================================
---- linux-2.6.git.orig/include/linux/sched.h
-+++ linux-2.6.git/include/linux/sched.h
-@@ -23,6 +23,7 @@
- #define CLONE_CHILD_SETTID	0x01000000	/* set the TID in the child */
- /* 0x02000000 was previously the unused CLONE_STOPPED (Start in stopped state)
-    and is now available for re-use. */
-+#define CLONE_CHILD_USEPID	0x02000000	/* use the given pid */
- #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
- #define CLONE_NEWIPC		0x08000000	/* New ipcs */
- #define CLONE_NEWUSER		0x10000000	/* New user namespace */
-Index: linux-2.6.git/kernel/fork.c
-===================================================================
---- linux-2.6.git.orig/kernel/fork.c
-+++ linux-2.6.git/kernel/fork.c
-@@ -1250,8 +1250,16 @@ static struct task_struct *copy_process(
- 		goto bad_fork_cleanup_io;
- 
- 	if (pid != &init_struct_pid) {
-+		int want_pid = 0;
-+
-+		if (clone_flags & CLONE_CHILD_USEPID) {
-+			retval = get_user(want_pid, child_tidptr);
-+			if (retval)
-+				goto bad_fork_cleanup_io;
-+		}
-+
- 		retval = -ENOMEM;
--		pid = alloc_pid(p->nsproxy->pid_ns);
-+		pid = alloc_pid(p->nsproxy->pid_ns, want_pid);
- 		if (!pid)
- 			goto bad_fork_cleanup_io;
- 	}
-Index: linux-2.6.git/kernel/pid.c
-===================================================================
---- linux-2.6.git.orig/kernel/pid.c
-+++ linux-2.6.git/kernel/pid.c
-@@ -159,11 +159,55 @@ static void set_last_pid(struct pid_name
- 	} while ((prev != last_write) && (pid_before(base, last_write, pid)));
- }
- 
--static int alloc_pidmap(struct pid_namespace *pid_ns)
-+static int alloc_pidmap_page(struct pidmap *map)
-+{
-+	if (unlikely(!map->page)) {
-+		void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
-+		/*
-+		 * Free the page if someone raced with us
-+		 * installing it:
-+		 */
-+		spin_lock_irq(&pidmap_lock);
-+		if (!map->page) {
-+			map->page = page;
-+			page = NULL;
-+		}
-+		spin_unlock_irq(&pidmap_lock);
-+		kfree(page);
-+		if (unlikely(!map->page))
-+			return -ENOMEM;
-+	}
-+
-+	return 0;
-+}
-+
-+static int set_pidmap(struct pid_namespace *pid_ns, int pid)
-+{
-+	int offset;
-+	struct pidmap *map;
-+
-+	offset = pid & BITS_PER_PAGE_MASK;
-+	map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
-+
-+	if (alloc_pidmap_page(map) < 0)
-+		return -ENOMEM;
-+
-+	if (!test_and_set_bit(offset, map->page)) {
-+		atomic_dec(&map->nr_free);
-+		return pid;
-+	}
-+
-+	return -EBUSY;
-+}
-+
-+static int alloc_pidmap(struct pid_namespace *pid_ns, int desired_pid)
- {
- 	int i, offset, max_scan, pid, last = pid_ns->last_pid;
- 	struct pidmap *map;
- 
-+	if (desired_pid)
-+		return set_pidmap(pid_ns, desired_pid);
-+
- 	pid = last + 1;
- 	if (pid >= pid_max)
- 		pid = RESERVED_PIDS;
-@@ -176,22 +220,9 @@ static int alloc_pidmap(struct pid_names
- 	 */
- 	max_scan = DIV_ROUND_UP(pid_max, BITS_PER_PAGE) - !offset;
- 	for (i = 0; i <= max_scan; ++i) {
--		if (unlikely(!map->page)) {
--			void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
--			/*
--			 * Free the page if someone raced with us
--			 * installing it:
--			 */
--			spin_lock_irq(&pidmap_lock);
--			if (!map->page) {
--				map->page = page;
--				page = NULL;
--			}
--			spin_unlock_irq(&pidmap_lock);
--			kfree(page);
--			if (unlikely(!map->page))
--				break;
--		}
-+		if (alloc_pidmap_page(map) < 0)
-+			break;
-+
- 		if (likely(atomic_read(&map->nr_free))) {
- 			do {
- 				if (!test_and_set_bit(offset, map->page)) {
-@@ -277,7 +308,7 @@ void free_pid(struct pid *pid)
- 	call_rcu(&pid->rcu, delayed_put_pid);
- }
- 
--struct pid *alloc_pid(struct pid_namespace *ns)
-+struct pid *alloc_pid(struct pid_namespace *ns, int this_ns_pid)
- {
- 	struct pid *pid;
- 	enum pid_type type;
-@@ -291,13 +322,14 @@ struct pid *alloc_pid(struct pid_namespa
- 
- 	tmp = ns;
- 	for (i = ns->level; i >= 0; i--) {
--		nr = alloc_pidmap(tmp);
-+		nr = alloc_pidmap(tmp, this_ns_pid);
- 		if (nr < 0)
- 			goto out_free;
- 
- 		pid->numbers[i].nr = nr;
- 		pid->numbers[i].ns = tmp;
- 		tmp = tmp->parent;
-+		this_ns_pid = 0;
- 	}
- 
- 	get_pid_ns(ns);

kernel/series

 fs-proc-Make-proc_get_link-to-use-dentry
 fs-proc-Introduce-the-proc-pid-map_files-directory
 procfs-introduce-the-proc-pid-map_files-directory-checkpatch
-clone-Introduce-the-CLONE_CHILD_USEPID-functionality
 fs-proc-Add-start_data-end_data-start_brk-members
 fs-proc-add-children-entry
 prctl-tune-up-mm_struct-members-2