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>

6 files changed, 27 insertions, 44 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 46f0fcc93081..d8cfb7b99a83 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2463,7 +2463,7 @@ int sysctl_compact_memory;
  * /proc/sys/vm/compact_memory
  */
 int sysctl_compaction_handler(struct ctl_table *table, int write,
-			void __user *buffer, size_t *length, loff_t *ppos)
+			void *buffer, size_t *length, loff_t *ppos)
 {
 	if (write)
 		compact_nodes();
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index cd459155d28a..2277c5728b1f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3352,7 +3352,7 @@ static unsigned int cpuset_mems_nr(unsigned int *array)
 #ifdef CONFIG_SYSCTL
 static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
 			 struct ctl_table *table, int write,
-			 void __user *buffer, size_t *length, loff_t *ppos)
+			 void *buffer, size_t *length, loff_t *ppos)
 {
 	struct hstate *h = &default_hstate;
 	unsigned long tmp = h->max_huge_pages;
@@ -3375,7 +3375,7 @@ out:
 }
 
 int hugetlb_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)
 {
 
 	return hugetlb_sysctl_handler_common(false, table, write,
@@ -3384,7 +3384,7 @@ int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 
 #ifdef CONFIG_NUMA
 int hugetlb_mempolicy_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)
 {
 	return hugetlb_sysctl_handler_common(true, table, write,
 							buffer, length, ppos);
@@ -3392,8 +3392,7 @@ int hugetlb_mempolicy_sysctl_handler(struct ctl_table *table, int write,
 #endif /* CONFIG_NUMA */
 
 int hugetlb_overcommit_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 hstate *h = &default_hstate;
 	unsigned long tmp;
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;
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;
diff --git a/mm/util.c b/mm/util.c
index 988d11e6c17c..8defc8ec141f 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -717,9 +717,8 @@ int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
 
-int overcommit_ratio_handler(struct ctl_table *table, int write,
-			     void __user *buffer, size_t *lenp,
-			     loff_t *ppos)
+int overcommit_ratio_handler(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
 {
 	int ret;
 
@@ -729,9 +728,8 @@ int overcommit_ratio_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
-int overcommit_kbytes_handler(struct ctl_table *table, int write,
-			     void __user *buffer, size_t *lenp,
-			     loff_t *ppos)
+int overcommit_kbytes_handler(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
 {
 	int ret;
 
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 96d21a792b57..c03a8c914922 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -76,7 +76,7 @@ static void invalid_numa_statistics(void)
 static DEFINE_MUTEX(vm_numa_stat_lock);
 
 int sysctl_vm_numa_stat_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 ret, oldval;
 
@@ -1751,7 +1751,7 @@ static void refresh_vm_stats(struct work_struct *work)
 }
 
 int vmstat_refresh(struct ctl_table *table, int write,
-		   void __user *buffer, size_t *lenp, loff_t *ppos)
+		   void *buffer, size_t *lenp, loff_t *ppos)
 {
 	long val;
 	int err;