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>

ipc/ipc_sysctl.c

@@ -24,7 +24,7 @@ static void *get_ipc(struct ctl_table *table)
 
 #ifdef CONFIG_PROC_SYSCTL
 static int proc_ipc_dointvec(struct ctl_table *table, int write,
-	void __user *buffer, size_t *lenp, loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table ipc_table;
 
@@ -35,7 +35,7 @@ static int proc_ipc_dointvec(struct ctl_table *table, int write,
 }
 
 static int proc_ipc_dointvec_minmax(struct ctl_table *table, int write,
-	void __user *buffer, size_t *lenp, loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table ipc_table;
 
@@ -46,7 +46,7 @@ static int proc_ipc_dointvec_minmax(struct ctl_table *table, int write,
 }
 
 static int proc_ipc_dointvec_minmax_orphans(struct ctl_table *table, int write,
-	void __user *buffer, size_t *lenp, loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ipc_namespace *ns = current->nsproxy->ipc_ns;
 	int err = proc_ipc_dointvec_minmax(table, write, buffer, lenp, ppos);
@@ -59,7 +59,7 @@ static int proc_ipc_dointvec_minmax_orphans(struct ctl_table *table, int write,
 }
 
 static int proc_ipc_doulongvec_minmax(struct ctl_table *table, int write,
-	void __user *buffer, size_t *lenp, loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table ipc_table;
 	memcpy(&ipc_table, table, sizeof(ipc_table));
@@ -70,7 +70,7 @@ static int proc_ipc_doulongvec_minmax(struct ctl_table *table, int write,
 }
 
 static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
-	void __user *buffer, size_t *lenp, loff_t *ppos)
+		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table ipc_table;
 	int dummy = 0;