linux/fs/kernfs/inode.c
Tejun Heo 4afddd60a7 kernfs: protect lazy kernfs_iattrs allocation with mutex
kernfs_iattrs is allocated lazily when operations which require it
take place; unfortunately, the lazy allocation and returning weren't
properly synchronized and when there are multiple concurrent
operations, it might end up returning kernfs_iattrs which hasn't
finished initialization yet or different copies to different callers.

Fix it by synchronizing with a mutex.  This can be smarter with memory
barriers but let's go there if it actually turns out to be necessary.

Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/g/533ABA32.9080602@oracle.com
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: stable@vger.kernel.org # 3.14
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-04-16 11:54:40 -07:00

384 lines
8.8 KiB
C

/*
* fs/kernfs/inode.c - kernfs inode implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*
* This file is released under the GPLv2.
*/
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include "kernfs-internal.h"
static const struct address_space_operations kernfs_aops = {
.readpage = simple_readpage,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
};
static struct backing_dev_info kernfs_bdi = {
.name = "kernfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
static const struct inode_operations kernfs_iops = {
.permission = kernfs_iop_permission,
.setattr = kernfs_iop_setattr,
.getattr = kernfs_iop_getattr,
.setxattr = kernfs_iop_setxattr,
.removexattr = kernfs_iop_removexattr,
.getxattr = kernfs_iop_getxattr,
.listxattr = kernfs_iop_listxattr,
};
void __init kernfs_inode_init(void)
{
if (bdi_init(&kernfs_bdi))
panic("failed to init kernfs_bdi");
}
static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
{
static DEFINE_MUTEX(iattr_mutex);
struct kernfs_iattrs *ret;
struct iattr *iattrs;
mutex_lock(&iattr_mutex);
if (kn->iattr)
goto out_unlock;
kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
if (!kn->iattr)
goto out_unlock;
iattrs = &kn->iattr->ia_iattr;
/* assign default attributes */
iattrs->ia_mode = kn->mode;
iattrs->ia_uid = GLOBAL_ROOT_UID;
iattrs->ia_gid = GLOBAL_ROOT_GID;
iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
simple_xattrs_init(&kn->iattr->xattrs);
out_unlock:
ret = kn->iattr;
mutex_unlock(&iattr_mutex);
return ret;
}
static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
struct kernfs_iattrs *attrs;
struct iattr *iattrs;
unsigned int ia_valid = iattr->ia_valid;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
iattrs = &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 = kn->mode = mode;
}
return 0;
}
/**
* kernfs_setattr - set iattr on a node
* @kn: target node
* @iattr: iattr to set
*
* Returns 0 on success, -errno on failure.
*/
int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
int ret;
mutex_lock(&kernfs_mutex);
ret = __kernfs_setattr(kn, iattr);
mutex_unlock(&kernfs_mutex);
return ret;
}
int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
{
struct inode *inode = dentry->d_inode;
struct kernfs_node *kn = dentry->d_fsdata;
int error;
if (!kn)
return -EINVAL;
mutex_lock(&kernfs_mutex);
error = inode_change_ok(inode, iattr);
if (error)
goto out;
error = __kernfs_setattr(kn, iattr);
if (error)
goto out;
/* this ignores size changes */
setattr_copy(inode, iattr);
out:
mutex_unlock(&kernfs_mutex);
return error;
}
static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
u32 *secdata_len)
{
struct kernfs_iattrs *attrs;
void *old_secdata;
size_t old_secdata_len;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
old_secdata = attrs->ia_secdata;
old_secdata_len = attrs->ia_secdata_len;
attrs->ia_secdata = *secdata;
attrs->ia_secdata_len = *secdata_len;
*secdata = old_secdata;
*secdata_len = old_secdata_len;
return 0;
}
int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_iattrs *attrs;
void *secdata;
int error;
u32 secdata_len = 0;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
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)
return error;
error = security_inode_getsecctx(dentry->d_inode,
&secdata, &secdata_len);
if (error)
return error;
mutex_lock(&kernfs_mutex);
error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
mutex_unlock(&kernfs_mutex);
if (secdata)
security_release_secctx(secdata, secdata_len);
return error;
} else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
return simple_xattr_set(&attrs->xattrs, name, value, size,
flags);
}
return -EINVAL;
}
int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_iattrs *attrs;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
return simple_xattr_remove(&attrs->xattrs, name);
}
ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
size_t size)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_iattrs *attrs;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
return simple_xattr_get(&attrs->xattrs, name, buf, size);
}
ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_iattrs *attrs;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
return simple_xattr_list(&attrs->xattrs, buf, size);
}
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 kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
{
struct kernfs_iattrs *attrs = kn->iattr;
inode->i_mode = kn->mode;
if (attrs) {
/*
* kernfs_node has non-default attributes get them from
* persistent copy in kernfs_node.
*/
set_inode_attr(inode, &attrs->ia_iattr);
security_inode_notifysecctx(inode, attrs->ia_secdata,
attrs->ia_secdata_len);
}
if (kernfs_type(kn) == KERNFS_DIR)
set_nlink(inode, kn->dir.subdirs + 2);
}
int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct inode *inode = dentry->d_inode;
mutex_lock(&kernfs_mutex);
kernfs_refresh_inode(kn, inode);
mutex_unlock(&kernfs_mutex);
generic_fillattr(inode, stat);
return 0;
}
static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
{
kernfs_get(kn);
inode->i_private = kn;
inode->i_mapping->a_ops = &kernfs_aops;
inode->i_mapping->backing_dev_info = &kernfs_bdi;
inode->i_op = &kernfs_iops;
set_default_inode_attr(inode, kn->mode);
kernfs_refresh_inode(kn, inode);
/* initialize inode according to type */
switch (kernfs_type(kn)) {
case KERNFS_DIR:
inode->i_op = &kernfs_dir_iops;
inode->i_fop = &kernfs_dir_fops;
break;
case KERNFS_FILE:
inode->i_size = kn->attr.size;
inode->i_fop = &kernfs_file_fops;
break;
case KERNFS_LINK:
inode->i_op = &kernfs_symlink_iops;
break;
default:
BUG();
}
unlock_new_inode(inode);
}
/**
* kernfs_get_inode - get inode for kernfs_node
* @sb: super block
* @kn: kernfs_node to allocate inode for
*
* Get inode for @kn. 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 *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
{
struct inode *inode;
inode = iget_locked(sb, kn->ino);
if (inode && (inode->i_state & I_NEW))
kernfs_init_inode(kn, inode);
return inode;
}
/*
* The kernfs_node serves as both an inode and a directory entry for
* kernfs. To prevent the kernfs inode numbers from being freed
* prematurely we take a reference to kernfs_node from the kernfs inode. A
* super_operations.evict_inode() implementation is needed to drop that
* reference upon inode destruction.
*/
void kernfs_evict_inode(struct inode *inode)
{
struct kernfs_node *kn = inode->i_private;
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
kernfs_put(kn);
}
int kernfs_iop_permission(struct inode *inode, int mask)
{
struct kernfs_node *kn;
if (mask & MAY_NOT_BLOCK)
return -ECHILD;
kn = inode->i_private;
mutex_lock(&kernfs_mutex);
kernfs_refresh_inode(kn, inode);
mutex_unlock(&kernfs_mutex);
return generic_permission(inode, mask);
}