sysctl: pass kernel pointers to ->proc_handler

Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/parport/procfs.c

@@ -34,7 +34,7 @@
 #define PARPORT_MAX_SPINTIME_VALUE 1000
 
 static int do_active_device(struct ctl_table *table, int write,
-		      void __user *result, size_t *lenp, loff_t *ppos)
+		      void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport *port = (struct parport *)table->extra1;
 	char buffer[256];
@@ -65,13 +65,13 @@ static int do_active_device(struct ctl_table *table, int write,
 		*lenp = len;
 
 	*ppos += len;
-
-	return copy_to_user(result, buffer, len) ? -EFAULT : 0;
+	memcpy(result, buffer, len);
+	return 0;
 }
 
 #ifdef CONFIG_PARPORT_1284
 static int do_autoprobe(struct ctl_table *table, int write,
-			void __user *result, size_t *lenp, loff_t *ppos)
+			void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport_device_info *info = table->extra2;
 	const char *str;
@@ -108,13 +108,13 @@ static int do_autoprobe(struct ctl_table *table, int write,
 
 	*ppos += len;
 
-	return copy_to_user (result, buffer, len) ? -EFAULT : 0;
+	memcpy(result, buffer, len);
+	return 0;
 }
 #endif /* IEEE1284.3 support. */
 
 static int do_hardware_base_addr(struct ctl_table *table, int write,
-				 void __user *result,
-				 size_t *lenp, loff_t *ppos)
+				 void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport *port = (struct parport *)table->extra1;
 	char buffer[20];
@@ -136,13 +136,12 @@ static int do_hardware_base_addr(struct ctl_table *table, int write,
 		*lenp = len;
 
 	*ppos += len;
-
-	return copy_to_user(result, buffer, len) ? -EFAULT : 0;
+	memcpy(result, buffer, len);
+	return 0;
 }
 
 static int do_hardware_irq(struct ctl_table *table, int write,
-			   void __user *result,
-			   size_t *lenp, loff_t *ppos)
+			   void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport *port = (struct parport *)table->extra1;
 	char buffer[20];
@@ -164,13 +163,12 @@ static int do_hardware_irq(struct ctl_table *table, int write,
 		*lenp = len;
 
 	*ppos += len;
-
-	return copy_to_user(result, buffer, len) ? -EFAULT : 0;
+	memcpy(result, buffer, len);
+	return 0;
 }
 
 static int do_hardware_dma(struct ctl_table *table, int write,
-			   void __user *result,
-			   size_t *lenp, loff_t *ppos)
+			   void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport *port = (struct parport *)table->extra1;
 	char buffer[20];
@@ -192,13 +190,12 @@ static int do_hardware_dma(struct ctl_table *table, int write,
 		*lenp = len;
 
 	*ppos += len;
-
-	return copy_to_user(result, buffer, len) ? -EFAULT : 0;
+	memcpy(result, buffer, len);
+	return 0;
 }
 
 static int do_hardware_modes(struct ctl_table *table, int write,
-			     void __user *result,
-			     size_t *lenp, loff_t *ppos)
+			     void *result, size_t *lenp, loff_t *ppos)
 {
 	struct parport *port = (struct parport *)table->extra1;
 	char buffer[40];
@@ -231,8 +228,8 @@ static int do_hardware_modes(struct ctl_table *table, int write,
 		*lenp = len;
 
 	*ppos += len;
-
-	return copy_to_user(result, buffer, len) ? -EFAULT : 0;
+	memcpy(result, buffer, len);
+	return 0;
 }
 
 #define PARPORT_PORT_DIR(CHILD) { .procname = NULL, .mode = 0555, .child = CHILD }