sysctl: Factor out sysctl_data.

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 situations 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@xmission.com>
Cc: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 47 insertions, 20 deletions

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index f73be4cd662e..5ca510b3cbe2 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 73c84b6e7a35..88c8ea8f5e8c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1443,7 +1443,6 @@ 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;
@@ -1464,25 +1463,10 @@ 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;
 }
@@ -2381,6 +2365,40 @@ 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,
@@ -2569,6 +2587,13 @@ 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)
@@ -2616,4 +2641,5 @@ 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);