fs: move fs/exec.c sysctls into its own file

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

So move the fs/exec.c respective sysctls to its own file.

Since checkpatch complains about style issues with the old code, this
move also fixes a few of those minor style issues:

  * Use pr_warn() instead of prink(WARNING
  * New empty lines are wanted at the beginning of routines

Link: https://lkml.kernel.org/r/20211129205548.605569-9-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/exec.c

@@ -65,6 +65,7 @@
 #include <linux/vmalloc.h>
 #include <linux/io_uring.h>
 #include <linux/syscall_user_dispatch.h>
+#include <linux/coredump.h>
 
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
@@ -2099,3 +2100,92 @@ COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
 				  argv, envp, flags);
 }
 #endif
+
+#ifdef CONFIG_SYSCTL
+
+static void validate_coredump_safety(void)
+{
+#ifdef CONFIG_COREDUMP
+	if (suid_dumpable == SUID_DUMP_ROOT &&
+	    core_pattern[0] != '/' && core_pattern[0] != '|') {
+		pr_warn(
+"Unsafe core_pattern used with fs.suid_dumpable=2.\n"
+"Pipe handler or fully qualified core dump path required.\n"
+"Set kernel.core_pattern before fs.suid_dumpable.\n"
+		);
+	}
+#endif
+}
+
+static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+	if (!error)
+		validate_coredump_safety();
+	return error;
+}
+
+static struct ctl_table fs_exec_sysctls[] = {
+	{
+		.procname	= "suid_dumpable",
+		.data		= &suid_dumpable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax_coredump,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
+	{ }
+};
+
+#ifdef CONFIG_COREDUMP
+
+static int proc_dostring_coredump(struct ctl_table *table, int write,
+		  void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int error = proc_dostring(table, write, buffer, lenp, ppos);
+
+	if (!error)
+		validate_coredump_safety();
+	return error;
+}
+
+static struct ctl_table kernel_exec_sysctls[] = {
+	{
+		.procname	= "core_uses_pid",
+		.data		= &core_uses_pid,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "core_pattern",
+		.data		= core_pattern,
+		.maxlen		= CORENAME_MAX_SIZE,
+		.mode		= 0644,
+		.proc_handler	= proc_dostring_coredump,
+	},
+	{
+		.procname	= "core_pipe_limit",
+		.data		= &core_pipe_limit,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{ }
+};
+#endif
+
+static int __init init_fs_exec_sysctls(void)
+{
+	register_sysctl_init("fs", fs_exec_sysctls);
+#ifdef CONFIG_COREDUMP
+	register_sysctl_init("kernel", kernel_exec_sysctls);
+#endif
+	return 0;
+}
+
+fs_initcall(init_fs_exec_sysctls);
+#endif /* CONFIG_SYSCTL */

kernel/sysctl.c

@@ -1117,40 +1117,6 @@ static int proc_dopipe_max_size(struct ctl_table *table, int write,
 				 do_proc_dopipe_max_size_conv, NULL);
 }
 
-static void validate_coredump_safety(void)
-{
-#ifdef CONFIG_COREDUMP
-	if (suid_dumpable == SUID_DUMP_ROOT &&
-	    core_pattern[0] != '/' && core_pattern[0] != '|') {
-		printk(KERN_WARNING
-"Unsafe core_pattern used with fs.suid_dumpable=2.\n"
-"Pipe handler or fully qualified core dump path required.\n"
-"Set kernel.core_pattern before fs.suid_dumpable.\n"
-		);
-	}
-#endif
-}
-
-static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
-		void *buffer, size_t *lenp, loff_t *ppos)
-{
-	int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-	if (!error)
-		validate_coredump_safety();
-	return error;
-}
-
-#ifdef CONFIG_COREDUMP
-static int proc_dostring_coredump(struct ctl_table *table, int write,
-		  void *buffer, size_t *lenp, loff_t *ppos)
-{
-	int error = proc_dostring(table, write, buffer, lenp, ppos);
-	if (!error)
-		validate_coredump_safety();
-	return error;
-}
-#endif
-
 #ifdef CONFIG_MAGIC_SYSRQ
 static int sysrq_sysctl_handler(struct ctl_table *table, int write,
 				void *buffer, size_t *lenp, loff_t *ppos)
@@ -1874,29 +1840,6 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
-#ifdef CONFIG_COREDUMP
-	{
-		.procname	= "core_uses_pid",
-		.data		= &core_uses_pid,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "core_pattern",
-		.data		= core_pattern,
-		.maxlen		= CORENAME_MAX_SIZE,
-		.mode		= 0644,
-		.proc_handler	= proc_dostring_coredump,
-	},
-	{
-		.procname	= "core_pipe_limit",
-		.data		= &core_pipe_limit,
-		.maxlen		= sizeof(unsigned int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-#endif
 #ifdef CONFIG_PROC_SYSCTL
 	{
 		.procname	= "tainted",
@@ -2897,15 +2840,6 @@ static struct ctl_table vm_table[] = {
 };
 
 static struct ctl_table fs_table[] = {
-	{
-		.procname	= "suid_dumpable",
-		.data		= &suid_dumpable,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax_coredump,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_TWO,
-	},
 	{
 		.procname	= "pipe-max-size",
 		.data		= &pipe_max_size,