linux/fs/sysfs/file.c
Joe Perches 2efc459d06 sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output
Output defects can exist in sysfs content using sprintf and snprintf.

sprintf does not know the PAGE_SIZE maximum of the temporary buffer
used for outputting sysfs content and it's possible to overrun the
PAGE_SIZE buffer length.

Add a generic sysfs_emit function that knows that the size of the
temporary buffer and ensures that no overrun is done.

Add a generic sysfs_emit_at function that can be used in multiple
call situations that also ensures that no overrun is done.

Validate the output buffer argument to be page aligned.
Validate the offset len argument to be within the PAGE_SIZE buf.

Signed-off-by: Joe Perches <joe@perches.com>
Link: https://lore.kernel.org/r/884235202216d464d61ee975f7465332c86f76b2.1600285923.git.joe@perches.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-10-02 12:02:30 +02:00

765 lines
18 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* fs/sysfs/file.c - sysfs regular (text) file implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
*
* Please see Documentation/filesystems/sysfs.rst for more information.
*/
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/seq_file.h>
#include <linux/mm.h>
#include "sysfs.h"
/*
* Determine ktype->sysfs_ops for the given kernfs_node. This function
* must be called while holding an active reference.
*/
static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
{
struct kobject *kobj = kn->parent->priv;
if (kn->flags & KERNFS_LOCKDEP)
lockdep_assert_held(kn);
return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
}
/*
* Reads on sysfs are handled through seq_file, which takes care of hairy
* details like buffering and seeking. The following function pipes
* sysfs_ops->show() result through seq_file.
*/
static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
{
struct kernfs_open_file *of = sf->private;
struct kobject *kobj = of->kn->parent->priv;
const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
ssize_t count;
char *buf;
/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
count = seq_get_buf(sf, &buf);
if (count < PAGE_SIZE) {
seq_commit(sf, -1);
return 0;
}
memset(buf, 0, PAGE_SIZE);
/*
* Invoke show(). Control may reach here via seq file lseek even
* if @ops->show() isn't implemented.
*/
if (ops->show) {
count = ops->show(kobj, of->kn->priv, buf);
if (count < 0)
return count;
}
/*
* The code works fine with PAGE_SIZE return but it's likely to
* indicate truncated result or overflow in normal use cases.
*/
if (count >= (ssize_t)PAGE_SIZE) {
printk("fill_read_buffer: %pS returned bad count\n",
ops->show);
/* Try to struggle along */
count = PAGE_SIZE - 1;
}
seq_commit(sf, count);
return 0;
}
static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
struct bin_attribute *battr = of->kn->priv;
struct kobject *kobj = of->kn->parent->priv;
loff_t size = file_inode(of->file)->i_size;
if (!count)
return 0;
if (size) {
if (pos >= size)
return 0;
if (pos + count > size)
count = size - pos;
}
if (!battr->read)
return -EIO;
return battr->read(of->file, kobj, battr, buf, pos, count);
}
/* kernfs read callback for regular sysfs files with pre-alloc */
static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
struct kobject *kobj = of->kn->parent->priv;
ssize_t len;
/*
* If buf != of->prealloc_buf, we don't know how
* large it is, so cannot safely pass it to ->show
*/
if (WARN_ON_ONCE(buf != of->prealloc_buf))
return 0;
len = ops->show(kobj, of->kn->priv, buf);
if (len < 0)
return len;
if (pos) {
if (len <= pos)
return 0;
len -= pos;
memmove(buf, buf + pos, len);
}
return min_t(ssize_t, count, len);
}
/* kernfs write callback for regular sysfs files */
static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
struct kobject *kobj = of->kn->parent->priv;
if (!count)
return 0;
return ops->store(kobj, of->kn->priv, buf, count);
}
/* kernfs write callback for bin sysfs files */
static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
struct bin_attribute *battr = of->kn->priv;
struct kobject *kobj = of->kn->parent->priv;
loff_t size = file_inode(of->file)->i_size;
if (size) {
if (size <= pos)
return -EFBIG;
count = min_t(ssize_t, count, size - pos);
}
if (!count)
return 0;
if (!battr->write)
return -EIO;
return battr->write(of->file, kobj, battr, buf, pos, count);
}
static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
struct vm_area_struct *vma)
{
struct bin_attribute *battr = of->kn->priv;
struct kobject *kobj = of->kn->parent->priv;
return battr->mmap(of->file, kobj, battr, vma);
}
void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
{
struct kernfs_node *kn = kobj->sd, *tmp;
if (kn && dir)
kn = kernfs_find_and_get(kn, dir);
else
kernfs_get(kn);
if (kn && attr) {
tmp = kernfs_find_and_get(kn, attr);
kernfs_put(kn);
kn = tmp;
}
if (kn) {
kernfs_notify(kn);
kernfs_put(kn);
}
}
EXPORT_SYMBOL_GPL(sysfs_notify);
static const struct kernfs_ops sysfs_file_kfops_empty = {
};
static const struct kernfs_ops sysfs_file_kfops_ro = {
.seq_show = sysfs_kf_seq_show,
};
static const struct kernfs_ops sysfs_file_kfops_wo = {
.write = sysfs_kf_write,
};
static const struct kernfs_ops sysfs_file_kfops_rw = {
.seq_show = sysfs_kf_seq_show,
.write = sysfs_kf_write,
};
static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
.read = sysfs_kf_read,
.prealloc = true,
};
static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
.write = sysfs_kf_write,
.prealloc = true,
};
static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
.read = sysfs_kf_read,
.write = sysfs_kf_write,
.prealloc = true,
};
static const struct kernfs_ops sysfs_bin_kfops_ro = {
.read = sysfs_kf_bin_read,
};
static const struct kernfs_ops sysfs_bin_kfops_wo = {
.write = sysfs_kf_bin_write,
};
static const struct kernfs_ops sysfs_bin_kfops_rw = {
.read = sysfs_kf_bin_read,
.write = sysfs_kf_bin_write,
};
static const struct kernfs_ops sysfs_bin_kfops_mmap = {
.read = sysfs_kf_bin_read,
.write = sysfs_kf_bin_write,
.mmap = sysfs_kf_bin_mmap,
};
int sysfs_add_file_mode_ns(struct kernfs_node *parent,
const struct attribute *attr, bool is_bin,
umode_t mode, kuid_t uid, kgid_t gid, const void *ns)
{
struct lock_class_key *key = NULL;
const struct kernfs_ops *ops;
struct kernfs_node *kn;
loff_t size;
if (!is_bin) {
struct kobject *kobj = parent->priv;
const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
/* every kobject with an attribute needs a ktype assigned */
if (WARN(!sysfs_ops, KERN_ERR
"missing sysfs attribute operations for kobject: %s\n",
kobject_name(kobj)))
return -EINVAL;
if (sysfs_ops->show && sysfs_ops->store) {
if (mode & SYSFS_PREALLOC)
ops = &sysfs_prealloc_kfops_rw;
else
ops = &sysfs_file_kfops_rw;
} else if (sysfs_ops->show) {
if (mode & SYSFS_PREALLOC)
ops = &sysfs_prealloc_kfops_ro;
else
ops = &sysfs_file_kfops_ro;
} else if (sysfs_ops->store) {
if (mode & SYSFS_PREALLOC)
ops = &sysfs_prealloc_kfops_wo;
else
ops = &sysfs_file_kfops_wo;
} else
ops = &sysfs_file_kfops_empty;
size = PAGE_SIZE;
} else {
struct bin_attribute *battr = (void *)attr;
if (battr->mmap)
ops = &sysfs_bin_kfops_mmap;
else if (battr->read && battr->write)
ops = &sysfs_bin_kfops_rw;
else if (battr->read)
ops = &sysfs_bin_kfops_ro;
else if (battr->write)
ops = &sysfs_bin_kfops_wo;
else
ops = &sysfs_file_kfops_empty;
size = battr->size;
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
if (!attr->ignore_lockdep)
key = attr->key ?: (struct lock_class_key *)&attr->skey;
#endif
kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
size, ops, (void *)attr, ns, key);
if (IS_ERR(kn)) {
if (PTR_ERR(kn) == -EEXIST)
sysfs_warn_dup(parent, attr->name);
return PTR_ERR(kn);
}
return 0;
}
/**
* sysfs_create_file_ns - create an attribute file for an object with custom ns
* @kobj: object we're creating for
* @attr: attribute descriptor
* @ns: namespace the new file should belong to
*/
int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
const void *ns)
{
kuid_t uid;
kgid_t gid;
if (WARN_ON(!kobj || !kobj->sd || !attr))
return -EINVAL;
kobject_get_ownership(kobj, &uid, &gid);
return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode,
uid, gid, ns);
}
EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
{
int err = 0;
int i;
for (i = 0; ptr[i] && !err; i++)
err = sysfs_create_file(kobj, ptr[i]);
if (err)
while (--i >= 0)
sysfs_remove_file(kobj, ptr[i]);
return err;
}
EXPORT_SYMBOL_GPL(sysfs_create_files);
/**
* sysfs_add_file_to_group - add an attribute file to a pre-existing group.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
* @group: group name.
*/
int sysfs_add_file_to_group(struct kobject *kobj,
const struct attribute *attr, const char *group)
{
struct kernfs_node *parent;
kuid_t uid;
kgid_t gid;
int error;
if (group) {
parent = kernfs_find_and_get(kobj->sd, group);
} else {
parent = kobj->sd;
kernfs_get(parent);
}
if (!parent)
return -ENOENT;
kobject_get_ownership(kobj, &uid, &gid);
error = sysfs_add_file_mode_ns(parent, attr, false,
attr->mode, uid, gid, NULL);
kernfs_put(parent);
return error;
}
EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
/**
* sysfs_chmod_file - update the modified mode value on an object attribute.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
* @mode: file permissions.
*
*/
int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
umode_t mode)
{
struct kernfs_node *kn;
struct iattr newattrs;
int rc;
kn = kernfs_find_and_get(kobj->sd, attr->name);
if (!kn)
return -ENOENT;
newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
newattrs.ia_valid = ATTR_MODE;
rc = kernfs_setattr(kn, &newattrs);
kernfs_put(kn);
return rc;
}
EXPORT_SYMBOL_GPL(sysfs_chmod_file);
/**
* sysfs_break_active_protection - break "active" protection
* @kobj: The kernel object @attr is associated with.
* @attr: The attribute to break the "active" protection for.
*
* With sysfs, just like kernfs, deletion of an attribute is postponed until
* all active .show() and .store() callbacks have finished unless this function
* is called. Hence this function is useful in methods that implement self
* deletion.
*/
struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
const struct attribute *attr)
{
struct kernfs_node *kn;
kobject_get(kobj);
kn = kernfs_find_and_get(kobj->sd, attr->name);
if (kn)
kernfs_break_active_protection(kn);
return kn;
}
EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
/**
* sysfs_unbreak_active_protection - restore "active" protection
* @kn: Pointer returned by sysfs_break_active_protection().
*
* Undo the effects of sysfs_break_active_protection(). Since this function
* calls kernfs_put() on the kernfs node that corresponds to the 'attr'
* argument passed to sysfs_break_active_protection() that attribute may have
* been removed between the sysfs_break_active_protection() and
* sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
* this function has returned.
*/
void sysfs_unbreak_active_protection(struct kernfs_node *kn)
{
struct kobject *kobj = kn->parent->priv;
kernfs_unbreak_active_protection(kn);
kernfs_put(kn);
kobject_put(kobj);
}
EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
/**
* sysfs_remove_file_ns - remove an object attribute with a custom ns tag
* @kobj: object we're acting for
* @attr: attribute descriptor
* @ns: namespace tag of the file to remove
*
* Hash the attribute name and namespace tag and kill the victim.
*/
void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
const void *ns)
{
struct kernfs_node *parent = kobj->sd;
kernfs_remove_by_name_ns(parent, attr->name, ns);
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
/**
* sysfs_remove_file_self - remove an object attribute from its own method
* @kobj: object we're acting for
* @attr: attribute descriptor
*
* See kernfs_remove_self() for details.
*/
bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
{
struct kernfs_node *parent = kobj->sd;
struct kernfs_node *kn;
bool ret;
kn = kernfs_find_and_get(parent, attr->name);
if (WARN_ON_ONCE(!kn))
return false;
ret = kernfs_remove_self(kn);
kernfs_put(kn);
return ret;
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
{
int i;
for (i = 0; ptr[i]; i++)
sysfs_remove_file(kobj, ptr[i]);
}
EXPORT_SYMBOL_GPL(sysfs_remove_files);
/**
* sysfs_remove_file_from_group - remove an attribute file from a group.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
* @group: group name.
*/
void sysfs_remove_file_from_group(struct kobject *kobj,
const struct attribute *attr, const char *group)
{
struct kernfs_node *parent;
if (group) {
parent = kernfs_find_and_get(kobj->sd, group);
} else {
parent = kobj->sd;
kernfs_get(parent);
}
if (parent) {
kernfs_remove_by_name(parent, attr->name);
kernfs_put(parent);
}
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
/**
* sysfs_create_bin_file - create binary file for object.
* @kobj: object.
* @attr: attribute descriptor.
*/
int sysfs_create_bin_file(struct kobject *kobj,
const struct bin_attribute *attr)
{
kuid_t uid;
kgid_t gid;
if (WARN_ON(!kobj || !kobj->sd || !attr))
return -EINVAL;
kobject_get_ownership(kobj, &uid, &gid);
return sysfs_add_file_mode_ns(kobj->sd, &attr->attr, true,
attr->attr.mode, uid, gid, NULL);
}
EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
/**
* sysfs_remove_bin_file - remove binary file for object.
* @kobj: object.
* @attr: attribute descriptor.
*/
void sysfs_remove_bin_file(struct kobject *kobj,
const struct bin_attribute *attr)
{
kernfs_remove_by_name(kobj->sd, attr->attr.name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
kgid_t kgid)
{
struct iattr newattrs = {
.ia_valid = ATTR_UID | ATTR_GID,
.ia_uid = kuid,
.ia_gid = kgid,
};
return kernfs_setattr(kn, &newattrs);
}
/**
* sysfs_link_change_owner - change owner of a sysfs file.
* @kobj: object of the kernfs_node the symlink is located in.
* @targ: object of the kernfs_node the symlink points to.
* @name: name of the link.
* @kuid: new owner's kuid
* @kgid: new owner's kgid
*
* This function looks up the sysfs symlink entry @name under @kobj and changes
* the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
* @targ.
*
* Returns 0 on success or error code on failure.
*/
int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
const char *name, kuid_t kuid, kgid_t kgid)
{
struct kernfs_node *kn = NULL;
int error;
if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
return -EINVAL;
error = -ENOENT;
kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
if (!kn)
goto out;
error = -EINVAL;
if (kernfs_type(kn) != KERNFS_LINK)
goto out;
if (kn->symlink.target_kn->priv != targ)
goto out;
error = internal_change_owner(kn, kuid, kgid);
out:
kernfs_put(kn);
return error;
}
/**
* sysfs_file_change_owner - change owner of a sysfs file.
* @kobj: object.
* @name: name of the file to change.
* @kuid: new owner's kuid
* @kgid: new owner's kgid
*
* This function looks up the sysfs entry @name under @kobj and changes the
* ownership to @kuid/@kgid.
*
* Returns 0 on success or error code on failure.
*/
int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
kgid_t kgid)
{
struct kernfs_node *kn;
int error;
if (!name)
return -EINVAL;
if (!kobj->state_in_sysfs)
return -EINVAL;
kn = kernfs_find_and_get(kobj->sd, name);
if (!kn)
return -ENOENT;
error = internal_change_owner(kn, kuid, kgid);
kernfs_put(kn);
return error;
}
EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
/**
* sysfs_change_owner - change owner of the given object.
* @kobj: object.
* @kuid: new owner's kuid
* @kgid: new owner's kgid
*
* Change the owner of the default directory, files, groups, and attributes of
* @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
* entries for a kobject are added by driver core. In summary,
* sysfs_change_owner() takes care of the default directory entry for @kobj,
* the default attributes associated with the ktype of @kobj and the default
* attributes associated with the ktype of @kobj.
* Additional properties not added by driver core have to be changed by the
* driver or subsystem which created them. This is similar to how
* driver/subsystem specific entries are removed.
*
* Returns 0 on success or error code on failure.
*/
int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
{
int error;
const struct kobj_type *ktype;
if (!kobj->state_in_sysfs)
return -EINVAL;
/* Change the owner of the kobject itself. */
error = internal_change_owner(kobj->sd, kuid, kgid);
if (error)
return error;
ktype = get_ktype(kobj);
if (ktype) {
struct attribute **kattr;
/*
* Change owner of the default attributes associated with the
* ktype of @kobj.
*/
for (kattr = ktype->default_attrs; kattr && *kattr; kattr++) {
error = sysfs_file_change_owner(kobj, (*kattr)->name,
kuid, kgid);
if (error)
return error;
}
/*
* Change owner of the default groups associated with the
* ktype of @kobj.
*/
error = sysfs_groups_change_owner(kobj, ktype->default_groups,
kuid, kgid);
if (error)
return error;
}
return 0;
}
EXPORT_SYMBOL_GPL(sysfs_change_owner);
/**
* sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
* @buf: start of PAGE_SIZE buffer.
* @fmt: format
* @...: optional arguments to @format
*
*
* Returns number of characters written to @buf.
*/
int sysfs_emit(char *buf, const char *fmt, ...)
{
va_list args;
int len;
if (WARN(!buf || offset_in_page(buf),
"invalid sysfs_emit: buf:%p\n", buf))
return 0;
va_start(args, fmt);
len = vscnprintf(buf, PAGE_SIZE, fmt, args);
va_end(args);
return len;
}
EXPORT_SYMBOL_GPL(sysfs_emit);
/**
* sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
* @buf: start of PAGE_SIZE buffer.
* @at: offset in @buf to start write in bytes
* @at must be >= 0 && < PAGE_SIZE
* @fmt: format
* @...: optional arguments to @fmt
*
*
* Returns number of characters written starting at &@buf[@at].
*/
int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
{
va_list args;
int len;
if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
"invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
return 0;
va_start(args, fmt);
len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
va_end(args);
return len;
}
EXPORT_SYMBOL_GPL(sysfs_emit_at);