kabi: reserve space for cred and user_namespace

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4MYYH
CVE: N/A

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

Reserve space in struct cred and struct user_namespace in advance to
prepare for merging a promising new feature [1] from kernel 5.14 and
some others in the future.

[1]: https://lkml.kernel.org/r/94d1dbecab060a6b116b0a2d1accd8ca1bbb4f5f.1619094428.git.legion@kernel.orgSigned-off-by: NGONG, Ruiqi <gongruiqi1@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Nweiyang wang <wangweiyang2@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

include/linux/cred.h

@@ -15,6 +15,7 @@
 #include <linux/uidgid.h>
 #include <linux/sched.h>
 #include <linux/sched/user.h>
+#include <linux/kabi.h>
 
 struct cred;
 struct inode;
@@ -150,6 +151,7 @@ struct cred {
 		int non_rcu;			/* Can we skip RCU deletion? */
 		struct rcu_head	rcu;		/* RCU deletion hook */
 	};
+	KABI_RESERVE(1)			/* reserved for ucounts */
 } __randomize_layout;
 
 extern void __put_cred(struct cred *);

include/linux/user_namespace.h

@@ -50,6 +50,26 @@ enum ucount_type {
 	UCOUNT_INOTIFY_INSTANCES,
 	UCOUNT_INOTIFY_WATCHES,
 #endif
+	/* These 15 members are reserved (with extra margin) for the future
+	 * enlargement of enum ucount_type, as how RH8.1 did it. This number
+	 * should be enough, as 6 of them are very likely to be used in the near
+	 * future.
+	 */
+	UCOUNT_KABI_RESERVE1,
+	UCOUNT_KABI_RESERVE2,
+	UCOUNT_KABI_RESERVE3,
+	UCOUNT_KABI_RESERVE4,
+	UCOUNT_KABI_RESERVE5,
+	UCOUNT_KABI_RESERVE6,
+	UCOUNT_KABI_RESERVE7,
+	UCOUNT_KABI_RESERVE8,
+	UCOUNT_KABI_RESERVE9,
+	UCOUNT_KABI_RESERVE10,
+	UCOUNT_KABI_RESERVE11,
+	UCOUNT_KABI_RESERVE12,
+	UCOUNT_KABI_RESERVE13,
+	UCOUNT_KABI_RESERVE14,
+	UCOUNT_KABI_RESERVE15,
 	UCOUNT_COUNTS,
 };
 

kernel/ucount.c

@@ -74,6 +74,22 @@ static struct ctl_table user_table[] = {
 	UCOUNT_ENTRY("max_inotify_instances"),
 	UCOUNT_ENTRY("max_inotify_watches"),
 #endif
+	/* These corresponds to the reservation in enum ucount_type */
+	{ }, // UCOUNT_KABI_RESERVE1
+	{ }, // UCOUNT_KABI_RESERVE2
+	{ }, // UCOUNT_KABI_RESERVE3
+	{ }, // UCOUNT_KABI_RESERVE4
+	{ }, // UCOUNT_KABI_RESERVE5
+	{ }, // UCOUNT_KABI_RESERVE6
+	{ }, // UCOUNT_KABI_RESERVE7
+	{ }, // UCOUNT_KABI_RESERVE8
+	{ }, // UCOUNT_KABI_RESERVE9
+	{ }, // UCOUNT_KABI_RESERVE10
+	{ }, // UCOUNT_KABI_RESERVE11
+	{ }, // UCOUNT_KABI_RESERVE12
+	{ }, // UCOUNT_KABI_RESERVE13
+	{ }, // UCOUNT_KABI_RESERVE14
+	{ }, // UCOUNT_KABI_RESERVE15
 	{ }
 };
 #endif /* CONFIG_SYSCTL */