pid: add pid reserve method for checkpoint and restore

hulk inclusion
category: feature
bugzilla: 48159
CVE: N/A

------------------------------

We record the pid of dump tasks in the reserved memory,
and reserve the pids before init task start.
In the recover process, free the reserved pids and
realloc them by setting fork_pid.
Signed-off-by: NJingxian He <hejingxian@huawei.com>
Reviewed-by: NJing Xiangfeng <jingxiangfeng@huawei.com>
Acked-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/char/pin_memory.c

@@ -39,12 +39,20 @@ struct pin_mem_area_set {
 #define _REMAP_PIN_MEM_AREA  3
 #define _FINISH_PIN_MEM_DUMP 4
 #define _INIT_PAGEMAP_READ   5
+#ifdef CONFIG_PID_RESERVE
+#define _SET_FORK_PID        6
+#define _PIN_MEM_IOC_MAX_NR  6
+#else
 #define _PIN_MEM_IOC_MAX_NR  5
+#endif
 #define SET_PIN_MEM_AREA        _IOW(PIN_MEM_MAGIC, _SET_PIN_MEM_AREA, struct pin_mem_area_set)
 #define CLEAR_PIN_MEM_AREA      _IOW(PIN_MEM_MAGIC, _CLEAR_PIN_MEM_AREA, int)
 #define REMAP_PIN_MEM_AREA      _IOW(PIN_MEM_MAGIC, _REMAP_PIN_MEM_AREA, int)
 #define FINISH_PIN_MEM_DUMP     _IOW(PIN_MEM_MAGIC, _FINISH_PIN_MEM_DUMP, int)
 #define INIT_PAGEMAP_READ       _IOW(PIN_MEM_MAGIC, _INIT_PAGEMAP_READ, int)
+#ifdef CONFIG_PID_RESERVE
+#define SET_FORK_PID            _IOW(PIN_MEM_MAGIC, _SET_FORK_PID, int)
+#endif
 static int set_pin_mem(struct pin_mem_area_set *pmas)
 {
 	int i;
@@ -145,6 +153,24 @@ static int pin_mem_remap(unsigned long arg)
 	return -EFAULT;
 }
 
+#ifdef CONFIG_PID_RESERVE
+static int set_fork_pid(unsigned long arg)
+{
+	int pid;
+	struct page_map_info *pmi = NULL;
+	void __user *buf = (void __user *)arg;
+
+	if (!access_ok(buf, sizeof(int)))
+		goto fault;
+	if (copy_from_user(&pid, buf, sizeof(int)))
+		goto fault;
+	current->fork_pid = pid;
+	return 0;
+fault:
+	return -EFAULT;
+}
+#endif
+
 static long pin_memory_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	long ret = 0;
@@ -170,6 +196,11 @@ static long pin_memory_ioctl(struct file *file, unsigned int cmd, unsigned long
 	case INIT_PAGEMAP_READ:
 		ret = init_pagemap_read();
 		break;
+#ifdef CONFIG_PID_RESERVE
+	case SET_FORK_PID:
+		ret = set_fork_pid(arg);
+		break;
+#endif
 	default:
 		return -EINVAL;
 	}

include/linux/pin_mem.h

@@ -89,5 +89,11 @@ extern struct resource pin_memory_resource;
 #endif
 extern void init_reserve_page_map(unsigned long map_addr, unsigned long map_size);
 
+#ifdef CONFIG_PID_RESERVE
+extern bool is_need_reserve_pids(void);
+extern void free_reserved_pid(struct idr *idr, int pid);
+extern void reserve_pids(struct idr *idr, int pid_max);
+#endif
+
 #endif /* CONFIG_PIN_MEMORY */
 #endif /* _LINUX_PIN_MEMORY_H */

include/linux/sched.h

@@ -1207,6 +1207,9 @@ struct task_struct {
 	/* Used by LSM modules for access restriction: */
 	void				*security;
 #endif
+#ifdef CONFIG_PID_RESERVE
+	int fork_pid;
+#endif
 
 	/*
 	 * New fields for task_struct should be added above here, so that

init/init_task.c

@@ -180,6 +180,9 @@ struct task_struct init_task
 #ifdef CONFIG_SECURITY
 	.security	= NULL,
 #endif
+#ifdef CONFIG_PID_RESERVE
+	.fork_pid = 0,
+#endif
 };
 EXPORT_SYMBOL(init_task);
 

kernel/pid.c

@@ -41,6 +41,9 @@
 #include <linux/sched/task.h>
 #include <linux/idr.h>
 #include <linux/kmemleak.h>
+#ifdef CONFIG_PID_RESERVE
+#include <linux/pin_mem.h>
+#endif
 
 struct pid init_struct_pid = {
 	.count 		= ATOMIC_INIT(1),
@@ -185,6 +188,27 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 		if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
 			pid_min = RESERVED_PIDS;
 
+#ifdef CONFIG_PID_RESERVE
+		if (!current->fork_pid) {
+			/*
+			 * Store a null pointer so find_pid_ns does not find
+			 * a partially initialized PID (see below).
+			 */
+			nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
+							  tmp->pid_max,
+							  GFP_ATOMIC);
+		} else {
+			/* Try to free the reserved fork_pid, and then use it to alloc pid. */
+			free_reserved_pid(&tmp->idr, current->fork_pid);
+			pid_min = current->fork_pid;
+			current->fork_pid = 0;
+			nr = idr_alloc(&tmp->idr, NULL, pid_min,
+				  pid_min + 1,
+				  GFP_ATOMIC);
+			if (nr == -ENOSPC)
+				nr = -EEXIST;
+		}
+#else
 		/*
 		 * Store a null pointer so find_pid_ns does not find
 		 * a partially initialized PID (see below).
@@ -192,6 +216,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 		nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
 				      tmp->pid_max,
 				      GFP_ATOMIC);
+#endif
 		spin_unlock_irq(&pidmap_lock);
 		idr_preload_end();
 
@@ -501,6 +526,10 @@ void __init pid_idr_init(void)
 	init_pid_ns.pid_cachep = KMEM_CACHE(pid,
 			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
 
+#ifdef CONFIG_PID_RESERVE
+	if (is_need_reserve_pids())
+		reserve_pids(&init_pid_ns.idr, pid_max);
+#endif
 	hdr = register_sysctl_paths(pid_kern_path, pid_ctl_table);
 	kmemleak_not_leak(hdr);
 }

mm/Kconfig

@@ -809,4 +809,14 @@ config PIN_MEMORY
 	  and restore. We can pin the memory data of tasks and collect
 	  the corresponding physical pages mapping info in checkpoint,
 	  and remap the physical pages to restore tasks in restore.
+
+config PID_RESERVE
+	bool "Support for reserve and recover pid"
+	depends on PIN_MEMORY
+	help
+	  Say y here to enable the pid reserved feature for checkpoint.
+	  and restore.
+	  We record the pid of dump task in the reserve memory,
+	  and reserve the pids before init task start. In restore process,
+	  free the reserved pids and realloc them for use.
 endmenu

mm/pin_mem.c

@@ -1071,4 +1071,55 @@ void clear_pin_memory_record(void)
 }
 EXPORT_SYMBOL_GPL(clear_pin_memory_record);
 
+#ifdef CONFIG_PID_RESERVE
+struct idr *reserve_idr;
+
+/* test if there exist pin memory tasks */
+bool is_need_reserve_pids(void)
+{
+	return (pin_pid_num > 0);
+}
+
+void free_reserved_pid(struct idr *idr, int pid)
+{
+	unsigned int index;
+	struct page_map_info *pmi;
+
+	if (!max_pin_pid_num || idr != reserve_idr)
+		return;
+
+	for (index = 0; index < pin_pid_num; index++) {
+		pmi = &(user_space_reserve_start[index]);
+		if (pmi->pid == pid && pmi->pid_reserved) {
+			idr_remove(idr, pid);
+			return;
+		}
+	}
+}
+
+/* reserve pids for check point tasks which pinned memory */
+void reserve_pids(struct idr *idr, int pid_max)
+{
+	int alloc_pid;
+	unsigned int index;
+	struct page_map_info *pmi;
+
+	if (!max_pin_pid_num)
+		return;
+	reserve_idr = idr;
+	for (index = 0; index < pin_pid_num; index++) {
+		pmi = &(user_space_reserve_start[index]);
+		pmi->pid_reserved = true;
+		alloc_pid = idr_alloc(idr, NULL, pmi->pid, pid_max, GFP_ATOMIC);
+		if (alloc_pid != pmi->pid) {
+			if (alloc_pid > 0)
+				idr_remove(idr, alloc_pid);
+			pr_warn("Reserve pid (%d) fail, real pid is %d.\n", alloc_pid, pmi->pid);
+			pmi->pid_reserved = false;
+			continue;
+		}
+	}
+}
+#endif /* CONFIG_PID_RESERVE */
+
 #endif /* CONFIG_PIN_MEMORY */