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, 10 insertions, 20 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62c1550cd43e..0c43e9ae5004 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5546,21 +5546,11 @@ char numa_zonelist_order[] = "Node";
  * sysctl handler for numa_zonelist_order
  */
 int numa_zonelist_order_handler(struct ctl_table *table, int write,
-		void __user *buffer, size_t *length,
-		loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
-	char *str;
-	int ret;
-
-	if (!write)
-		return proc_dostring(table, write, buffer, length, ppos);
-	str = memdup_user_nul(buffer, 16);
-	if (IS_ERR(str))
-		return PTR_ERR(str);
-
-	ret = __parse_numa_zonelist_order(str);
-	kfree(str);
-	return ret;
+	if (write)
+		return __parse_numa_zonelist_order(buffer);
+	return proc_dostring(table, write, buffer, length, ppos);
 }
 
 
@@ -7963,7 +7953,7 @@ core_initcall(init_per_zone_wmark_min)
  *	changes.
  */
 int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	int rc;
 
@@ -7979,7 +7969,7 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
 }
 
 int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	int rc;
 
@@ -8009,7 +7999,7 @@ static void setup_min_unmapped_ratio(void)
 
 
 int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	int rc;
 
@@ -8036,7 +8026,7 @@ static void setup_min_slab_ratio(void)
 }
 
 int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	int rc;
 
@@ -8060,7 +8050,7 @@ int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
  * if in function of the boot time zone sizes.
  */
 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	proc_dointvec_minmax(table, write, buffer, length, ppos);
 	setup_per_zone_lowmem_reserve();
@@ -8082,7 +8072,7 @@ static void __zone_pcp_update(struct zone *zone)
  * pagelist can have before it gets flushed back to buddy allocator.
  */
 int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *table, int write,
-	void __user *buffer, size_t *length, loff_t *ppos)
+		void *buffer, size_t *length, loff_t *ppos)
 {
 	struct zone *zone;
 	int old_percpu_pagelist_fraction;