1 files changed, 145 insertions, 0 deletions
diff --git a/kernel/utsname_sysctl.c b/kernel/utsname_sysctl.c
new file mode 100644
index 0000000000..019e3a1566
--- /dev/null
+++ b/kernel/utsname_sysctl.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 2007
+ *
+ *  Author: Eric Biederman <ebiederm@xmision.com>
+ */
+
+#include <linux/export.h>
+#include <linux/uts.h>
+#include <linux/utsname.h>
+#include <linux/random.h>
+#include <linux/sysctl.h>
+#include <linux/wait.h>
+#include <linux/rwsem.h>
+
+#ifdef CONFIG_PROC_SYSCTL
+
+static void *get_uts(struct ctl_table *table)
+{
+	char *which = table->data;
+	struct uts_namespace *uts_ns;
+
+	uts_ns = current->nsproxy->uts_ns;
+	which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
+
+	return which;
+}
+
+/*
+ *	Special case of dostring for the UTS structure. This has locks
+ *	to observe. Should this be in kernel/sys.c ????
+ */
+static int proc_do_uts_string(struct ctl_table *table, int write,
+		  void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table uts_table;
+	int r;
+	char tmp_data[__NEW_UTS_LEN + 1];
+
+	memcpy(&uts_table, table, sizeof(uts_table));
+	uts_table.data = tmp_data;
+
+	/*
+	 * Buffer the value in tmp_data so that proc_dostring() can be called
+	 * without holding any locks.
+	 * We also need to read the original value in the write==1 case to
+	 * support partial writes.
+	 */
+	down_read(&uts_sem);
+	memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
+	up_read(&uts_sem);
+	r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
+
+	if (write) {
+		/*
+		 * Write back the new value.
+		 * Note that, since we dropped uts_sem, the result can
+		 * theoretically be incorrect if there are two parallel writes
+		 * at non-zero offsets to the same sysctl.
+		 */
+		add_device_randomness(tmp_data, sizeof(tmp_data));
+		down_write(&uts_sem);
+		memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
+		up_write(&uts_sem);
+		proc_sys_poll_notify(table->poll);
+	}
+
+	return r;
+}
+#else
+#define proc_do_uts_string NULL
+#endif
+
+static DEFINE_CTL_TABLE_POLL(hostname_poll);
+static DEFINE_CTL_TABLE_POLL(domainname_poll);
+
+// Note: update 'enum uts_proc' to match any changes to this table
+static struct ctl_table uts_kern_table[] = {
+	{
+		.procname	= "arch",
+		.data		= init_uts_ns.name.machine,
+		.maxlen		= sizeof(init_uts_ns.name.machine),
+		.mode		= 0444,
+		.proc_handler	= proc_do_uts_string,
+	},
+	{
+		.procname	= "ostype",
+		.data		= init_uts_ns.name.sysname,
+		.maxlen		= sizeof(init_uts_ns.name.sysname),
+		.mode		= 0444,
+		.proc_handler	= proc_do_uts_string,
+	},
+	{
+		.procname	= "osrelease",
+		.data		= init_uts_ns.name.release,
+		.maxlen		= sizeof(init_uts_ns.name.release),
+		.mode		= 0444,
+		.proc_handler	= proc_do_uts_string,
+	},
+	{
+		.procname	= "version",
+		.data		= init_uts_ns.name.version,
+		.maxlen		= sizeof(init_uts_ns.name.version),
+		.mode		= 0444,
+		.proc_handler	= proc_do_uts_string,
+	},
+	{
+		.procname	= "hostname",
+		.data		= init_uts_ns.name.nodename,
+		.maxlen		= sizeof(init_uts_ns.name.nodename),
+		.mode		= 0644,
+		.proc_handler	= proc_do_uts_string,
+		.poll		= &hostname_poll,
+	},
+	{
+		.procname	= "domainname",
+		.data		= init_uts_ns.name.domainname,
+		.maxlen		= sizeof(init_uts_ns.name.domainname),
+		.mode		= 0644,
+		.proc_handler	= proc_do_uts_string,
+		.poll		= &domainname_poll,
+	},
+	{}
+};
+
+#ifdef CONFIG_PROC_SYSCTL
+/*
+ * Notify userspace about a change in a certain entry of uts_kern_table,
+ * identified by the parameter proc.
+ */
+void uts_proc_notify(enum uts_proc proc)
+{
+	struct ctl_table *table = &uts_kern_table[proc];
+
+	proc_sys_poll_notify(table->poll);
+}
+#endif
+
+static int __init utsname_sysctl_init(void)
+{
+	register_sysctl("kernel", uts_kern_table);
+	return 0;
+}
+
+device_initcall(utsname_sysctl_init);