pid: fix pid recover method kabi change

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

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

Pid recover method add new member to task_truct,
which generates kabi change problem.
We use KABI_RESERVE of task_truct, instead of
adding new member to task_truct.
Signed-off-by: NJingxian He <hejingxian@huawei.com>
Reviewed-by: NJing Xiangfeng <jingxiangfeng@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/char/pin_memory.c

@@ -164,7 +164,7 @@ static int set_fork_pid(unsigned long arg)
 		goto fault;
 	if (copy_from_user(&pid, buf, sizeof(int)))
 		goto fault;
-	current->fork_pid = pid;
+	current->fork_pid_union.fork_pid = pid;
 	return 0;
 fault:
 	return -EFAULT;

include/linux/sched.h

@@ -596,6 +596,13 @@ struct wake_q_node {
 	struct wake_q_node *next;
 };
 
+#ifdef CONFIG_PID_RESERVE
+typedef union {
+	pid_t fork_pid;
+	unsigned long pid_reserve;
+} fork_pid_t;
+#endif
+
 struct task_struct {
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 	/*
@@ -1206,9 +1213,6 @@ 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
@@ -1227,7 +1231,15 @@ struct task_struct {
 	KABI_RESERVE(3)
 	KABI_RESERVE(4)
 #endif
+#ifdef CONFIG_PID_RESERVE
+#ifndef __GENKSYMS__
+	fork_pid_t fork_pid_union;
+#else
+	KABI_RESERVE(5)
+#endif
+#else
 	KABI_RESERVE(5)
+#endif
 	KABI_RESERVE(6)
 	KABI_RESERVE(7)
 	KABI_RESERVE(8)

init/init_task.c

@@ -181,7 +181,9 @@ struct task_struct init_task
 	.security	= NULL,
 #endif
 #ifdef CONFIG_PID_RESERVE
-	.fork_pid = 0,
+	.fork_pid_union = {
+		.fork_pid = 0,
+	},
 #endif
 };
 EXPORT_SYMBOL(init_task);

kernel/pid.c

@@ -189,7 +189,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 			pid_min = RESERVED_PIDS;
 
 #ifdef CONFIG_PID_RESERVE
-		if (!current->fork_pid) {
+		if (!current->fork_pid_union.fork_pid) {
 			/*
 			 * Store a null pointer so find_pid_ns does not find
 			 * a partially initialized PID (see below).
@@ -199,9 +199,9 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 							  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;
+			free_reserved_pid(&tmp->idr, current->fork_pid_union.fork_pid);
+			pid_min = current->fork_pid_union.fork_pid;
+			current->fork_pid_union.fork_pid = 0;
 			nr = idr_alloc(&tmp->idr, NULL, pid_min,
 				  pid_min + 1,
 				  GFP_ATOMIC);