[PATCH] sysctl: implement sysctl_uts_string()

The problem: When using sys_sysctl we don't read the proper values for the
variables exported from the uts namespace, nor do we do the proper locking.

This patch introduces sysctl_uts_string which properly fetches the values and
does the proper locking.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/sysctl.c

@@ -137,6 +137,10 @@ static int parse_table(int __user *, int, void __user *, size_t __user *,
 static int proc_do_uts_string(ctl_table *table, int write, struct file *filp,
 		  void __user *buffer, size_t *lenp, loff_t *ppos);
 
+static int sysctl_uts_string(ctl_table *table, int __user *name, int nlen,
+		  void __user *oldval, size_t __user *oldlenp,
+		  void __user *newval, size_t newlen, void **context);
+
 #ifdef CONFIG_PROC_SYSCTL
 static int proc_do_cad_pid(ctl_table *table, int write, struct file *filp,
 		  void __user *buffer, size_t *lenp, loff_t *ppos);
@@ -258,7 +262,7 @@ static ctl_table kern_table[] = {
 		.maxlen		= sizeof(init_uts_ns.name.sysname),
 		.mode		= 0444,
 		.proc_handler	= &proc_do_uts_string,
-		.strategy	= &sysctl_string,
+		.strategy	= &sysctl_uts_string,
 	},
 	{
 		.ctl_name	= KERN_OSRELEASE,
@@ -267,7 +271,7 @@ static ctl_table kern_table[] = {
 		.maxlen		= sizeof(init_uts_ns.name.release),
 		.mode		= 0444,
 		.proc_handler	= &proc_do_uts_string,
-		.strategy	= &sysctl_string,
+		.strategy	= &sysctl_uts_string,
 	},
 	{
 		.ctl_name	= KERN_VERSION,
@@ -276,7 +280,7 @@ static ctl_table kern_table[] = {
 		.maxlen		= sizeof(init_uts_ns.name.version),
 		.mode		= 0444,
 		.proc_handler	= &proc_do_uts_string,
-		.strategy	= &sysctl_string,
+		.strategy	= &sysctl_uts_string,
 	},
 	{
 		.ctl_name	= KERN_NODENAME,
@@ -285,7 +289,7 @@ static ctl_table kern_table[] = {
 		.maxlen		= sizeof(init_uts_ns.name.nodename),
 		.mode		= 0644,
 		.proc_handler	= &proc_do_uts_string,
-		.strategy	= &sysctl_string,
+		.strategy	= &sysctl_uts_string,
 	},
 	{
 		.ctl_name	= KERN_DOMAINNAME,
@@ -294,7 +298,7 @@ static ctl_table kern_table[] = {
 		.maxlen		= sizeof(init_uts_ns.name.domainname),
 		.mode		= 0644,
 		.proc_handler	= &proc_do_uts_string,
-		.strategy	= &sysctl_string,
+		.strategy	= &sysctl_uts_string,
 	},
 	{
 		.ctl_name	= KERN_PANIC,
@@ -2598,6 +2602,23 @@ int sysctl_ms_jiffies(ctl_table *table, int __user *name, int nlen,
 	return 1;
 }
 
+
+/* The generic string strategy routine: */
+static int sysctl_uts_string(ctl_table *table, int __user *name, int nlen,
+		  void __user *oldval, size_t __user *oldlenp,
+		  void __user *newval, size_t newlen, void **context)
+{
+	struct ctl_table uts_table;
+	int r, write;
+	write = newval && newlen;
+	memcpy(&uts_table, table, sizeof(uts_table));
+	uts_table.data = get_uts(table, write);
+	r = sysctl_string(&uts_table, name, nlen,
+		oldval, oldlenp, newval, newlen, context);
+	put_uts(table, write, uts_table.data);
+	return r;
+}
+
 #else /* CONFIG_SYSCTL_SYSCALL */
 
 
@@ -2662,6 +2683,12 @@ int sysctl_ms_jiffies(ctl_table *table, int __user *name, int nlen,
 	return -ENOSYS;
 }
 
+static int sysctl_uts_string(ctl_table *table, int __user *name, int nlen,
+		  void __user *oldval, size_t __user *oldlenp,
+		  void __user *newval, size_t newlen, void **context)
+{
+	return -ENOSYS;
+}
 #endif /* CONFIG_SYSCTL_SYSCALL */
 
 /*