security: min_addr: move sysctl to security/min_addr.c

The dac_mmap_min_addr belongs to min_addr.c, move it to
min_addr.c from /kernel/sysctl.c. In the previous Linux kernel
boot process, sysctl_init_bases needs to be executed before
init_mmap_min_addr, So, register_sysctl_init should be executed
before update_mmap_min_addr in init_mmap_min_addr. And according
to the compilation condition in security/Makefile:

      obj-$(CONFIG_MMU)            += min_addr.o

if CONFIG_MMU is not defined, min_addr.c would not be included in the
compilation process. So, drop the CONFIG_MMU check.

Signed-off-by: Kaixiong Yu <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Acked-by: Paul Moore <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Signed-off-by: Joel Granados <[email protected]>

Author: yukaixiong

kernel/sysctl.c

@@ -2049,15 +2049,6 @@ static const struct ctl_table vm_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
 	},
-#ifdef CONFIG_MMU
-	{
-		.procname	= "mmap_min_addr",
-		.data		= &dac_mmap_min_addr,
-		.maxlen		= sizeof(unsigned long),
-		.mode		= 0644,
-		.proc_handler	= mmap_min_addr_handler,
-	},
-#endif
 #if (defined(CONFIG_X86_32) && !defined(CONFIG_UML))|| \
    (defined(CONFIG_SUPERH) && defined(CONFIG_VSYSCALL))
 	{

security/min_addr.c

@@ -44,8 +44,19 @@ int mmap_min_addr_handler(const struct ctl_table *table, int write,
 	return ret;
 }
 
+static const struct ctl_table min_addr_sysctl_table[] = {
+	{
+		.procname	= "mmap_min_addr",
+		.data		= &dac_mmap_min_addr,
+		.maxlen		= sizeof(unsigned long),
+		.mode		= 0644,
+		.proc_handler	= mmap_min_addr_handler,
+	},
+};
+
 static int __init init_mmap_min_addr(void)
 {
+	register_sysctl_init("vm", min_addr_sysctl_table);
 	update_mmap_min_addr();
 
 	return 0;