[Devel] [PATCH 2/3] sysctl: Factor out sysctl_data.

[Eric W. Biederman]

There as been no easy way to wrap the default sysctl strategy routine
except for returning 0.  Which is not always what we want.  The few
instances I have seen that want different behaviour have written their own
version of sysctl_data.  While not too hard it is unnecessary code and
has the potential for extra bugs.

So to make these situnations easier and make that part of sysctl
more symetric I have factord sysctl_data out of do_sysctl_strategy
and exported as a function everyone can use.

Further having sysctl_data be an explicit function makes checking
for badly formed sysctl tables much easier.

Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
---
 include/linux/sysctl.h |    1 +
 kernel/sysctl.c        |   66 +++++++++++++++++++++++++++++++++--------------
 2 files changed, 47 insertions(+), 20 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index f73be4c..5ca510b 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -972,6 +972,7 @@ extern int do_sysctl_strategy (struct ctl_table *table,
 			       void __user *oldval, size_t __user *oldlenp,
 			       void __user *newval, size_t newlen);
 
+extern ctl_handler sysctl_data;
 extern ctl_handler sysctl_string;
 extern ctl_handler sysctl_intvec;
 extern ctl_handler sysctl_jiffies;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6723f92..cf4c632 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1406,7 +1406,6 @@ int do_sysctl_strategy (struct ctl_table *table,
 			void __user *newval, size_t newlen)
 {
 	int op = 0, rc;
-	size_t len;
 
 	if (oldval)
 		op |= 004;
@@ -1427,25 +1426,10 @@ int do_sysctl_strategy (struct ctl_table *table,
 	/* If there is no strategy routine, or if the strategy returns
 	 * zero, proceed with automatic r/w */
 	if (table->data && table->maxlen) {
-		if (oldval && oldlenp) {
-			if (get_user(len, oldlenp))
-				return -EFAULT;
-			if (len) {
-				if (len > table->maxlen)
-					len = table->maxlen;
-				if(copy_to_user(oldval, table->data, len))
-					return -EFAULT;
-				if(put_user(len, oldlenp))
-					return -EFAULT;
-			}
-		}
-		if (newval && newlen) {
-			len = newlen;
-			if (len > table->maxlen)
-				len = table->maxlen;
-			if(copy_from_user(table->data, newval, len))
-				return -EFAULT;
-		}
+		rc = sysctl_data(table, name, nlen, oldval, oldlenp,
+				 newval, newlen);
+		if (rc < 0)
+			return rc;
 	}
 	return 0;
 }
@@ -2344,6 +2328,40 @@ int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int write,
  * General sysctl support routines 
  */
 
+/* The generic sysctl data routine (used if no strategy routine supplied) */
+int sysctl_data(struct ctl_table *table, int __user *name, int nlen,
+		void __user *oldval, size_t __user *oldlenp,
+		void __user *newval, size_t newlen)
+{
+	size_t len;
+
+	/* Get out of I don't have a variable */
+	if (!table->data || !table->maxlen)
+		return -ENOTDIR;
+
+	if (oldval && oldlenp) {
+		if (get_user(len, oldlenp))
+			return -EFAULT;
+		if (len) {
+			if (len > table->maxlen)
+				len = table->maxlen;
+			if (copy_to_user(oldval, table->data, len))
+				return -EFAULT;
+			if (put_user(len, oldlenp))
+				return -EFAULT;
+		}
+	}
+
+	if (newval && newlen) {
+		if (newlen > table->maxlen)
+			newlen = table->maxlen;
+
+		if (copy_from_user(table->data, newval, newlen))
+			return -EFAULT;
+	}
+	return 1;
+}
+
 /* The generic string strategy routine: */
 int sysctl_string(struct ctl_table *table, int __user *name, int nlen,
 		  void __user *oldval, size_t __user *oldlenp,
@@ -2532,6 +2550,13 @@ out:
 	return -ENOSYS;
 }
 
+int sysctl_data(struct ctl_table *table, int __user *name, int nlen,
+		  void __user *oldval, size_t __user *oldlenp,
+		  void __user *newval, size_t newlen)
+{
+	return -ENOSYS;
+}
+
 int sysctl_string(struct ctl_table *table, int __user *name, int nlen,
 		  void __user *oldval, size_t __user *oldlenp,
 		  void __user *newval, size_t newlen)
@@ -2579,4 +2604,5 @@ EXPORT_SYMBOL(sysctl_intvec);
 EXPORT_SYMBOL(sysctl_jiffies);
 EXPORT_SYMBOL(sysctl_ms_jiffies);
 EXPORT_SYMBOL(sysctl_string);
+EXPORT_SYMBOL(sysctl_data);
 EXPORT_SYMBOL(unregister_sysctl_table);
-- 
1.5.1.1.181.g2de0