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>

1 files changed, 6 insertions, 10 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7326b54ab728..d3ee4c4dafac 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -512,8 +512,7 @@ bool node_dirty_ok(struct pglist_data *pgdat)
 }
 
 int dirty_background_ratio_handler(struct ctl_table *table, int write,
-		void __user *buffer, size_t *lenp,
-		loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int ret;
 
@@ -524,8 +523,7 @@ int dirty_background_ratio_handler(struct ctl_table *table, int write,
 }
 
 int dirty_background_bytes_handler(struct ctl_table *table, int write,
-		void __user *buffer, size_t *lenp,
-		loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int ret;
 
@@ -535,9 +533,8 @@ int dirty_background_bytes_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
-int dirty_ratio_handler(struct ctl_table *table, int write,
-		void __user *buffer, size_t *lenp,
-		loff_t *ppos)
+int dirty_ratio_handler(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
 {
 	int old_ratio = vm_dirty_ratio;
 	int ret;
@@ -551,8 +548,7 @@ int dirty_ratio_handler(struct ctl_table *table, int write,
 }
 
 int dirty_bytes_handler(struct ctl_table *table, int write,
-		void __user *buffer, size_t *lenp,
-		loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	unsigned long old_bytes = vm_dirty_bytes;
 	int ret;
@@ -1972,7 +1968,7 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
  * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
  */
 int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	unsigned int old_interval = dirty_writeback_interval;
 	int ret;