linux/fs/fuse/control.c
Kees Cook 3f649ab728 treewide: Remove uninitialized_var() usage
Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB
Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers
Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs
Signed-off-by: Kees Cook <keescook@chromium.org>
2020-07-16 12:35:15 -07:00

392 lines
8.7 KiB
C

/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2008 Miklos Szeredi <miklos@szeredi.hu>
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
*/
#include "fuse_i.h"
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs_context.h>
#define FUSE_CTL_SUPER_MAGIC 0x65735543
/*
* This is non-NULL when the single instance of the control filesystem
* exists. Protected by fuse_mutex
*/
static struct super_block *fuse_control_sb;
static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
{
struct fuse_conn *fc;
mutex_lock(&fuse_mutex);
fc = file_inode(file)->i_private;
if (fc)
fc = fuse_conn_get(fc);
mutex_unlock(&fuse_mutex);
return fc;
}
static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (fc) {
if (fc->abort_err)
fc->aborted = true;
fuse_abort_conn(fc);
fuse_conn_put(fc);
}
return count;
}
static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
char tmp[32];
size_t size;
if (!*ppos) {
long value;
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
value = atomic_read(&fc->num_waiting);
file->private_data = (void *)value;
fuse_conn_put(fc);
}
size = sprintf(tmp, "%ld\n", (long)file->private_data);
return simple_read_from_buffer(buf, len, ppos, tmp, size);
}
static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos, unsigned val)
{
char tmp[32];
size_t size = sprintf(tmp, "%u\n", val);
return simple_read_from_buffer(buf, len, ppos, tmp, size);
}
static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos, unsigned *val,
unsigned global_limit)
{
unsigned long t;
unsigned limit = (1 << 16) - 1;
int err;
if (*ppos)
return -EINVAL;
err = kstrtoul_from_user(buf, count, 0, &t);
if (err)
return err;
if (!capable(CAP_SYS_ADMIN))
limit = min(limit, global_limit);
if (t > limit)
return -EINVAL;
*val = t;
return count;
}
static ssize_t fuse_conn_max_background_read(struct file *file,
char __user *buf, size_t len,
loff_t *ppos)
{
struct fuse_conn *fc;
unsigned val;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
val = READ_ONCE(fc->max_background);
fuse_conn_put(fc);
return fuse_conn_limit_read(file, buf, len, ppos, val);
}
static ssize_t fuse_conn_max_background_write(struct file *file,
const char __user *buf,
size_t count, loff_t *ppos)
{
unsigned val;
ssize_t ret;
ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
max_user_bgreq);
if (ret > 0) {
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (fc) {
spin_lock(&fc->bg_lock);
fc->max_background = val;
fc->blocked = fc->num_background >= fc->max_background;
if (!fc->blocked)
wake_up(&fc->blocked_waitq);
spin_unlock(&fc->bg_lock);
fuse_conn_put(fc);
}
}
return ret;
}
static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
char __user *buf, size_t len,
loff_t *ppos)
{
struct fuse_conn *fc;
unsigned val;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
val = READ_ONCE(fc->congestion_threshold);
fuse_conn_put(fc);
return fuse_conn_limit_read(file, buf, len, ppos, val);
}
static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
const char __user *buf,
size_t count, loff_t *ppos)
{
unsigned val;
struct fuse_conn *fc;
ssize_t ret;
ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
max_user_congthresh);
if (ret <= 0)
goto out;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
goto out;
spin_lock(&fc->bg_lock);
fc->congestion_threshold = val;
if (fc->sb) {
if (fc->num_background < fc->congestion_threshold) {
clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
} else {
set_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
}
}
spin_unlock(&fc->bg_lock);
fuse_conn_put(fc);
out:
return ret;
}
static const struct file_operations fuse_ctl_abort_ops = {
.open = nonseekable_open,
.write = fuse_conn_abort_write,
.llseek = no_llseek,
};
static const struct file_operations fuse_ctl_waiting_ops = {
.open = nonseekable_open,
.read = fuse_conn_waiting_read,
.llseek = no_llseek,
};
static const struct file_operations fuse_conn_max_background_ops = {
.open = nonseekable_open,
.read = fuse_conn_max_background_read,
.write = fuse_conn_max_background_write,
.llseek = no_llseek,
};
static const struct file_operations fuse_conn_congestion_threshold_ops = {
.open = nonseekable_open,
.read = fuse_conn_congestion_threshold_read,
.write = fuse_conn_congestion_threshold_write,
.llseek = no_llseek,
};
static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
struct fuse_conn *fc,
const char *name,
int mode, int nlink,
const struct inode_operations *iop,
const struct file_operations *fop)
{
struct dentry *dentry;
struct inode *inode;
BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
dentry = d_alloc_name(parent, name);
if (!dentry)
return NULL;
inode = new_inode(fuse_control_sb);
if (!inode) {
dput(dentry);
return NULL;
}
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_uid = fc->user_id;
inode->i_gid = fc->group_id;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
/* setting ->i_op to NULL is not allowed */
if (iop)
inode->i_op = iop;
inode->i_fop = fop;
set_nlink(inode, nlink);
inode->i_private = fc;
d_add(dentry, inode);
fc->ctl_dentry[fc->ctl_ndents++] = dentry;
return dentry;
}
/*
* Add a connection to the control filesystem (if it exists). Caller
* must hold fuse_mutex
*/
int fuse_ctl_add_conn(struct fuse_conn *fc)
{
struct dentry *parent;
char name[32];
if (!fuse_control_sb)
return 0;
parent = fuse_control_sb->s_root;
inc_nlink(d_inode(parent));
sprintf(name, "%u", fc->dev);
parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
&simple_dir_inode_operations,
&simple_dir_operations);
if (!parent)
goto err;
if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
NULL, &fuse_ctl_waiting_ops) ||
!fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
NULL, &fuse_ctl_abort_ops) ||
!fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
1, NULL, &fuse_conn_max_background_ops) ||
!fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
S_IFREG | 0600, 1, NULL,
&fuse_conn_congestion_threshold_ops))
goto err;
return 0;
err:
fuse_ctl_remove_conn(fc);
return -ENOMEM;
}
/*
* Remove a connection from the control filesystem (if it exists).
* Caller must hold fuse_mutex
*/
void fuse_ctl_remove_conn(struct fuse_conn *fc)
{
int i;
if (!fuse_control_sb)
return;
for (i = fc->ctl_ndents - 1; i >= 0; i--) {
struct dentry *dentry = fc->ctl_dentry[i];
d_inode(dentry)->i_private = NULL;
if (!i) {
/* Get rid of submounts: */
d_invalidate(dentry);
}
dput(dentry);
}
drop_nlink(d_inode(fuse_control_sb->s_root));
}
static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fctx)
{
static const struct tree_descr empty_descr = {""};
struct fuse_conn *fc;
int err;
err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
if (err)
return err;
mutex_lock(&fuse_mutex);
BUG_ON(fuse_control_sb);
fuse_control_sb = sb;
list_for_each_entry(fc, &fuse_conn_list, entry) {
err = fuse_ctl_add_conn(fc);
if (err) {
fuse_control_sb = NULL;
mutex_unlock(&fuse_mutex);
return err;
}
}
mutex_unlock(&fuse_mutex);
return 0;
}
static int fuse_ctl_get_tree(struct fs_context *fc)
{
return get_tree_single(fc, fuse_ctl_fill_super);
}
static const struct fs_context_operations fuse_ctl_context_ops = {
.get_tree = fuse_ctl_get_tree,
};
static int fuse_ctl_init_fs_context(struct fs_context *fc)
{
fc->ops = &fuse_ctl_context_ops;
return 0;
}
static void fuse_ctl_kill_sb(struct super_block *sb)
{
struct fuse_conn *fc;
mutex_lock(&fuse_mutex);
fuse_control_sb = NULL;
list_for_each_entry(fc, &fuse_conn_list, entry)
fc->ctl_ndents = 0;
mutex_unlock(&fuse_mutex);
kill_litter_super(sb);
}
static struct file_system_type fuse_ctl_fs_type = {
.owner = THIS_MODULE,
.name = "fusectl",
.init_fs_context = fuse_ctl_init_fs_context,
.kill_sb = fuse_ctl_kill_sb,
};
MODULE_ALIAS_FS("fusectl");
int __init fuse_ctl_init(void)
{
return register_filesystem(&fuse_ctl_fs_type);
}
void __exit fuse_ctl_cleanup(void)
{
unregister_filesystem(&fuse_ctl_fs_type);
}