[PATCH 7/9] sysctl: Convert to iter interfaces

Christoph Hellwig
2020-06-26T07:59:20Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Using the read_iter/write_iter interfaces allows for in-kernel users
to set sysctls without using set_fs(). Also, the buffer is a string,
so give it the real type of 'char *', not void *.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/proc/proc_sysctl.c | 44 ++++++++++++++++++--------------------
include/linux/bpf-cgroup.h | 2 +-
kernel/bpf/cgroup.c | 2 +-
3 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 6c1166ccdaea57..9f6b9c3e3fdaf5 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -12,6 +12,7 @@
#include <linux/cred.h>
#include <linux/namei.h>
#include <linux/mm.h>
+#include <linux/uio.h>
#include <linux/module.h>
#include <linux/bpf-cgroup.h>
#include <linux/mount.h>
@@ -540,13 +541,14 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
return err;
}

-static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
- size_t count, loff_t *ppos, int write)
+static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
+ int write)
{
- struct inode *inode = file_inode(filp);
+ struct inode *inode = file_inode(iocb->ki_filp);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
- void *kbuf;
+ size_t count = iov_iter_count(iter);
+ char *kbuf;
ssize_t error;

if (IS_ERR(head))
@@ -569,32 +571,30 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
error = -ENOMEM;
if (count >= KMALLOC_MAX_SIZE)
goto out;
+ kbuf = kzalloc(count + 1, GFP_KERNEL);
+ if (!kbuf)
+ goto out;

if (write) {
- kbuf = memdup_user_nul(ubuf, count);
- if (IS_ERR(kbuf)) {
- error = PTR_ERR(kbuf);
- goto out;
- }
- } else {
- kbuf = kzalloc(count, GFP_KERNEL);
- if (!kbuf)
+ error = -EFAULT;
+ if (!copy_from_iter_full(kbuf, count, iter))
goto out;
+ kbuf[count] = '\0';
}

error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
- ppos);
+ &iocb->ki_pos);
if (error)
goto out_free_buf;

/* careful: calling conventions are nasty here */
- error = table->proc_handler(table, write, kbuf, &count, ppos);
+ error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos);
if (error)
goto out_free_buf;

if (!write) {
error = -EFAULT;
- if (copy_to_user(ubuf, kbuf, count))
+ if (copy_to_iter(kbuf, count, iter) < count)
goto out_free_buf;
}

@@ -607,16 +607,14 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
return error;
}

-static ssize_t proc_sys_read(struct file *filp, char __user *buf,
- size_t count, loff_t *ppos)
+static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter)
{
- return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
+ return proc_sys_call_handler(iocb, iter, 0);
}

-static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
- size_t count, loff_t *ppos)
+static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter)
{
- return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
+ return proc_sys_call_handler(iocb, iter, 1);
}

static int proc_sys_open(struct inode *inode, struct file *filp)
@@ -853,8 +851,8 @@ static int proc_sys_getattr(const struct path *path, struct kstat *stat,
static const struct file_operations proc_sys_file_operations = {
.open = proc_sys_open,
.poll = proc_sys_poll,
- .read = proc_sys_read,
- .write = proc_sys_write,
+ .read_iter = proc_sys_read,
+ .write_iter = proc_sys_write,
.llseek = default_llseek,
};

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index c66c545e161a60..f81d3b3752f919 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -132,7 +132,7 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,

int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
struct ctl_table *table, int write,
- void **buf, size_t *pcount, loff_t *ppos,
+ char **buf, size_t *pcount, loff_t *ppos,
enum bpf_attach_type type);

int __cgroup_bpf_run_filter_setsockopt(struct sock *sock, int *level,
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 4d76f16524cc44..45a918fc573d0a 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1202,7 +1202,7 @@ const struct bpf_verifier_ops cg_dev_verifier_ops = {
*/
int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
struct ctl_table *table, int write,
- void **buf, size_t *pcount, loff_t *ppos,
+ char **buf, size_t *pcount, loff_t *ppos,
enum bpf_attach_type type)
{
struct bpf_sysctl_kern ctx = {
--
2.26.2