linux/fs/sysfs/inode.c
Eric W. Biederman ce59791936 sysfs: Complain bitterly about attempts to remove files from nonexistent directories.
Recently an OOPS was observed from the usb serial io_ti driver when it tried to remove
sysfs directories.  Upon investigation it turns out this driver was always buggy
and that a recent sysfs change had stopped guarding itself against removing attributes
from sysfs directories that had already been removed. :(

Historically we have been silent about attempting to files from nonexistent sysfs
directories and have politely returned error codes.  That has resulted in people writing
broken code that ignores the error codes.

Issue a kernel WARNING and a stack backtrace to make it clear in no uncertain
terms that abusing sysfs is not ok, and the callers need to fix their code.

This change transforms the io_ti OOPS into a more comprehensible error message
and stack backtrace.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Reported-by: Wolfgang Frisch <wfpub@roembden.net>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2012-01-24 12:12:32 -08:00

356 lines
8.2 KiB
C

/*
* fs/sysfs/inode.c - basic sysfs inode and dentry operations
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
*
* This file is released under the GPLv2.
*
* Please see Documentation/filesystems/sysfs.txt for more information.
*/
#undef DEBUG
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include "sysfs.h"
extern struct super_block * sysfs_sb;
static const struct address_space_operations sysfs_aops = {
.readpage = simple_readpage,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
};
static struct backing_dev_info sysfs_backing_dev_info = {
.name = "sysfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
static const struct inode_operations sysfs_inode_operations ={
.permission = sysfs_permission,
.setattr = sysfs_setattr,
.getattr = sysfs_getattr,
.setxattr = sysfs_setxattr,
};
int __init sysfs_inode_init(void)
{
return bdi_init(&sysfs_backing_dev_info);
}
static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
{
struct sysfs_inode_attrs *attrs;
struct iattr *iattrs;
attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
if (!attrs)
return NULL;
iattrs = &attrs->ia_iattr;
/* assign default attributes */
iattrs->ia_mode = sd->s_mode;
iattrs->ia_uid = 0;
iattrs->ia_gid = 0;
iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
return attrs;
}
int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)
{
struct sysfs_inode_attrs *sd_attrs;
struct iattr *iattrs;
unsigned int ia_valid = iattr->ia_valid;
sd_attrs = sd->s_iattr;
if (!sd_attrs) {
/* setting attributes for the first time, allocate now */
sd_attrs = sysfs_init_inode_attrs(sd);
if (!sd_attrs)
return -ENOMEM;
sd->s_iattr = sd_attrs;
}
/* attributes were changed at least once in past */
iattrs = &sd_attrs->ia_iattr;
if (ia_valid & ATTR_UID)
iattrs->ia_uid = iattr->ia_uid;
if (ia_valid & ATTR_GID)
iattrs->ia_gid = iattr->ia_gid;
if (ia_valid & ATTR_ATIME)
iattrs->ia_atime = iattr->ia_atime;
if (ia_valid & ATTR_MTIME)
iattrs->ia_mtime = iattr->ia_mtime;
if (ia_valid & ATTR_CTIME)
iattrs->ia_ctime = iattr->ia_ctime;
if (ia_valid & ATTR_MODE) {
umode_t mode = iattr->ia_mode;
iattrs->ia_mode = sd->s_mode = mode;
}
return 0;
}
int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
struct inode *inode = dentry->d_inode;
struct sysfs_dirent *sd = dentry->d_fsdata;
int error;
if (!sd)
return -EINVAL;
mutex_lock(&sysfs_mutex);
error = inode_change_ok(inode, iattr);
if (error)
goto out;
error = sysfs_sd_setattr(sd, iattr);
if (error)
goto out;
/* this ignores size changes */
setattr_copy(inode, iattr);
out:
mutex_unlock(&sysfs_mutex);
return error;
}
static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
{
struct sysfs_inode_attrs *iattrs;
void *old_secdata;
size_t old_secdata_len;
iattrs = sd->s_iattr;
if (!iattrs)
iattrs = sysfs_init_inode_attrs(sd);
if (!iattrs)
return -ENOMEM;
old_secdata = iattrs->ia_secdata;
old_secdata_len = iattrs->ia_secdata_len;
iattrs->ia_secdata = *secdata;
iattrs->ia_secdata_len = *secdata_len;
*secdata = old_secdata;
*secdata_len = old_secdata_len;
return 0;
}
int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags)
{
struct sysfs_dirent *sd = dentry->d_fsdata;
void *secdata;
int error;
u32 secdata_len = 0;
if (!sd)
return -EINVAL;
if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
error = security_inode_setsecurity(dentry->d_inode, suffix,
value, size, flags);
if (error)
goto out;
error = security_inode_getsecctx(dentry->d_inode,
&secdata, &secdata_len);
if (error)
goto out;
mutex_lock(&sysfs_mutex);
error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
mutex_unlock(&sysfs_mutex);
if (secdata)
security_release_secctx(secdata, secdata_len);
} else
return -EINVAL;
out:
return error;
}
static inline void set_default_inode_attr(struct inode * inode, umode_t mode)
{
inode->i_mode = mode;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
}
static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
{
inode->i_uid = iattr->ia_uid;
inode->i_gid = iattr->ia_gid;
inode->i_atime = iattr->ia_atime;
inode->i_mtime = iattr->ia_mtime;
inode->i_ctime = iattr->ia_ctime;
}
static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
{
struct sysfs_inode_attrs *iattrs = sd->s_iattr;
inode->i_mode = sd->s_mode;
if (iattrs) {
/* sysfs_dirent has non-default attributes
* get them from persistent copy in sysfs_dirent
*/
set_inode_attr(inode, &iattrs->ia_iattr);
security_inode_notifysecctx(inode,
iattrs->ia_secdata,
iattrs->ia_secdata_len);
}
if (sysfs_type(sd) == SYSFS_DIR)
set_nlink(inode, sd->s_dir.subdirs + 2);
}
int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
struct sysfs_dirent *sd = dentry->d_fsdata;
struct inode *inode = dentry->d_inode;
mutex_lock(&sysfs_mutex);
sysfs_refresh_inode(sd, inode);
mutex_unlock(&sysfs_mutex);
generic_fillattr(inode, stat);
return 0;
}
static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
{
struct bin_attribute *bin_attr;
inode->i_private = sysfs_get(sd);
inode->i_mapping->a_ops = &sysfs_aops;
inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
inode->i_op = &sysfs_inode_operations;
set_default_inode_attr(inode, sd->s_mode);
sysfs_refresh_inode(sd, inode);
/* initialize inode according to type */
switch (sysfs_type(sd)) {
case SYSFS_DIR:
inode->i_op = &sysfs_dir_inode_operations;
inode->i_fop = &sysfs_dir_operations;
break;
case SYSFS_KOBJ_ATTR:
inode->i_size = PAGE_SIZE;
inode->i_fop = &sysfs_file_operations;
break;
case SYSFS_KOBJ_BIN_ATTR:
bin_attr = sd->s_bin_attr.bin_attr;
inode->i_size = bin_attr->size;
inode->i_fop = &bin_fops;
break;
case SYSFS_KOBJ_LINK:
inode->i_op = &sysfs_symlink_inode_operations;
break;
default:
BUG();
}
unlock_new_inode(inode);
}
/**
* sysfs_get_inode - get inode for sysfs_dirent
* @sb: super block
* @sd: sysfs_dirent to allocate inode for
*
* Get inode for @sd. If such inode doesn't exist, a new inode
* is allocated and basics are initialized. New inode is
* returned locked.
*
* LOCKING:
* Kernel thread context (may sleep).
*
* RETURNS:
* Pointer to allocated inode on success, NULL on failure.
*/
struct inode * sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)
{
struct inode *inode;
inode = iget_locked(sb, sd->s_ino);
if (inode && (inode->i_state & I_NEW))
sysfs_init_inode(sd, inode);
return inode;
}
/*
* The sysfs_dirent serves as both an inode and a directory entry for sysfs.
* To prevent the sysfs inode numbers from being freed prematurely we take a
* reference to sysfs_dirent from the sysfs inode. A
* super_operations.evict_inode() implementation is needed to drop that
* reference upon inode destruction.
*/
void sysfs_evict_inode(struct inode *inode)
{
struct sysfs_dirent *sd = inode->i_private;
truncate_inode_pages(&inode->i_data, 0);
end_writeback(inode);
sysfs_put(sd);
}
int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name)
{
struct sysfs_addrm_cxt acxt;
struct sysfs_dirent *sd;
if (!dir_sd) {
WARN(1, KERN_WARNING "sysfs: can not remove '%s', no directory\n",
name);
return -ENOENT;
}
sysfs_addrm_start(&acxt, dir_sd);
sd = sysfs_find_dirent(dir_sd, ns, name);
if (sd)
sysfs_remove_one(&acxt, sd);
sysfs_addrm_finish(&acxt);
if (sd)
return 0;
else
return -ENOENT;
}
int sysfs_permission(struct inode *inode, int mask)
{
struct sysfs_dirent *sd;
if (mask & MAY_NOT_BLOCK)
return -ECHILD;
sd = inode->i_private;
mutex_lock(&sysfs_mutex);
sysfs_refresh_inode(sd, inode);
mutex_unlock(&sysfs_mutex);
return generic_permission(inode, mask);
}