[PATCH 2/4] sysctl: Implement sysctl_uts_string

["Eric W. Biederman" <ebiederm@xmission.com>]

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>
---
 kernel/sysctl.c |   37 ++++++++++++++++++++++++++++++++-----
 1 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 0521884..63db5a5 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -136,6 +136,10 @@ #endif
 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);
@@ -257,7 +261,7 @@ 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,
@@ -266,7 +270,7 @@ 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,
@@ -275,7 +279,7 @@ 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,
@@ -284,7 +288,7 @@ 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,
@@ -293,7 +297,7 @@ 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,
@@ -2600,6 +2604,23 @@ int sysctl_ms_jiffies(ctl_table *table, 
 	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 */
 
 
@@ -2664,6 +2685,12 @@ int sysctl_ms_jiffies(ctl_table *table, 
 	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 */
 
 /*
-- 
1.4.2.rc3.g7e18e-dirty