/
inode.c
1148 lines (971 loc) · 30.3 KB
/
inode.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
*
* Copyright (C) 2011 Novell Inc.
*/
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/ratelimit.h>
#include <linux/fiemap.h>
#include <linux/fileattr.h>
#include <linux/security.h>
#include "overlayfs.h"
int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
struct iattr *attr)
{
int err;
bool full_copy_up = false;
struct dentry *upperdentry;
const struct cred *old_cred;
err = setattr_prepare(&init_user_ns, dentry, attr);
if (err)
return err;
err = ovl_want_write(dentry);
if (err)
goto out;
if (attr->ia_valid & ATTR_SIZE) {
struct inode *realinode = d_inode(ovl_dentry_real(dentry));
err = -ETXTBSY;
if (atomic_read(&realinode->i_writecount) < 0)
goto out_drop_write;
/* Truncate should trigger data copy up as well */
full_copy_up = true;
}
if (!full_copy_up)
err = ovl_copy_up(dentry);
else
err = ovl_copy_up_with_data(dentry);
if (!err) {
struct inode *winode = NULL;
upperdentry = ovl_dentry_upper(dentry);
if (attr->ia_valid & ATTR_SIZE) {
winode = d_inode(upperdentry);
err = get_write_access(winode);
if (err)
goto out_drop_write;
}
if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
attr->ia_valid &= ~ATTR_MODE;
/*
* We might have to translate ovl file into real file object
* once use cases emerge. For now, simply don't let underlying
* filesystem rely on attr->ia_file
*/
attr->ia_valid &= ~ATTR_FILE;
/*
* If open(O_TRUNC) is done, VFS calls ->setattr with ATTR_OPEN
* set. Overlayfs does not pass O_TRUNC flag to underlying
* filesystem during open -> do not pass ATTR_OPEN. This
* disables optimization in fuse which assumes open(O_TRUNC)
* already set file size to 0. But we never passed O_TRUNC to
* fuse. So by clearing ATTR_OPEN, fuse will be forced to send
* setattr request to server.
*/
attr->ia_valid &= ~ATTR_OPEN;
inode_lock(upperdentry->d_inode);
old_cred = ovl_override_creds(dentry->d_sb);
err = notify_change(&init_user_ns, upperdentry, attr, NULL);
revert_creds(old_cred);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
inode_unlock(upperdentry->d_inode);
if (winode)
put_write_access(winode);
}
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
static void ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
{
bool samefs = ovl_same_fs(dentry->d_sb);
unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
unsigned int xinoshift = 64 - xinobits;
if (samefs) {
/*
* When all layers are on the same fs, all real inode
* number are unique, so we use the overlay st_dev,
* which is friendly to du -x.
*/
stat->dev = dentry->d_sb->s_dev;
return;
} else if (xinobits) {
/*
* All inode numbers of underlying fs should not be using the
* high xinobits, so we use high xinobits to partition the
* overlay st_ino address space. The high bits holds the fsid
* (upper fsid is 0). The lowest xinobit is reserved for mapping
* the non-persistent inode numbers range in case of overflow.
* This way all overlay inode numbers are unique and use the
* overlay st_dev.
*/
if (likely(!(stat->ino >> xinoshift))) {
stat->ino |= ((u64)fsid) << (xinoshift + 1);
stat->dev = dentry->d_sb->s_dev;
return;
} else if (ovl_xino_warn(dentry->d_sb)) {
pr_warn_ratelimited("inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
dentry, stat->ino, xinobits);
}
}
/* The inode could not be mapped to a unified st_ino address space */
if (S_ISDIR(dentry->d_inode->i_mode)) {
/*
* Always use the overlay st_dev for directories, so 'find
* -xdev' will scan the entire overlay mount and won't cross the
* overlay mount boundaries.
*
* If not all layers are on the same fs the pair {real st_ino;
* overlay st_dev} is not unique, so use the non persistent
* overlay st_ino for directories.
*/
stat->dev = dentry->d_sb->s_dev;
stat->ino = dentry->d_inode->i_ino;
} else {
/*
* For non-samefs setup, if we cannot map all layers st_ino
* to a unified address space, we need to make sure that st_dev
* is unique per underlying fs, so we use the unique anonymous
* bdev assigned to the underlying fs.
*/
stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;
}
}
int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
struct kstat *stat, u32 request_mask, unsigned int flags)
{
struct dentry *dentry = path->dentry;
enum ovl_path_type type;
struct path realpath;
const struct cred *old_cred;
bool is_dir = S_ISDIR(dentry->d_inode->i_mode);
int fsid = 0;
int err;
bool metacopy_blocks = false;
metacopy_blocks = ovl_is_metacopy_dentry(dentry);
type = ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getattr(&realpath, stat, request_mask, flags);
if (err)
goto out;
/*
* For non-dir or same fs, we use st_ino of the copy up origin.
* This guaranties constant st_dev/st_ino across copy up.
* With xino feature and non-samefs, we use st_ino of the copy up
* origin masked with high bits that represent the layer id.
*
* If lower filesystem supports NFS file handles, this also guaranties
* persistent st_ino across mount cycle.
*/
if (!is_dir || ovl_same_dev(dentry->d_sb)) {
if (!OVL_TYPE_UPPER(type)) {
fsid = ovl_layer_lower(dentry)->fsid;
} else if (OVL_TYPE_ORIGIN(type)) {
struct kstat lowerstat;
u32 lowermask = STATX_INO | STATX_BLOCKS |
(!is_dir ? STATX_NLINK : 0);
ovl_path_lower(dentry, &realpath);
err = vfs_getattr(&realpath, &lowerstat,
lowermask, flags);
if (err)
goto out;
/*
* Lower hardlinks may be broken on copy up to different
* upper files, so we cannot use the lower origin st_ino
* for those different files, even for the same fs case.
*
* Similarly, several redirected dirs can point to the
* same dir on a lower layer. With the "verify_lower"
* feature, we do not use the lower origin st_ino, if
* we haven't verified that this redirect is unique.
*
* With inodes index enabled, it is safe to use st_ino
* of an indexed origin. The index validates that the
* upper hardlink is not broken and that a redirected
* dir is the only redirect to that origin.
*/
if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||
(!ovl_verify_lower(dentry->d_sb) &&
(is_dir || lowerstat.nlink == 1))) {
fsid = ovl_layer_lower(dentry)->fsid;
stat->ino = lowerstat.ino;
}
/*
* If we are querying a metacopy dentry and lower
* dentry is data dentry, then use the blocks we
* queried just now. We don't have to do additional
* vfs_getattr(). If lower itself is metacopy, then
* additional vfs_getattr() is unavoidable.
*/
if (metacopy_blocks &&
realpath.dentry == ovl_dentry_lowerdata(dentry)) {
stat->blocks = lowerstat.blocks;
metacopy_blocks = false;
}
}
if (metacopy_blocks) {
/*
* If lower is not same as lowerdata or if there was
* no origin on upper, we can end up here.
*/
struct kstat lowerdatastat;
u32 lowermask = STATX_BLOCKS;
ovl_path_lowerdata(dentry, &realpath);
err = vfs_getattr(&realpath, &lowerdatastat,
lowermask, flags);
if (err)
goto out;
stat->blocks = lowerdatastat.blocks;
}
}
ovl_map_dev_ino(dentry, stat, fsid);
/*
* It's probably not worth it to count subdirs to get the
* correct link count. nlink=1 seems to pacify 'find' and
* other utilities.
*/
if (is_dir && OVL_TYPE_MERGE(type))
stat->nlink = 1;
/*
* Return the overlay inode nlinks for indexed upper inodes.
* Overlay inode nlink counts the union of the upper hardlinks
* and non-covered lower hardlinks. It does not include the upper
* index hardlink.
*/
if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
stat->nlink = dentry->d_inode->i_nlink;
out:
revert_creds(old_cred);
return err;
}
int ovl_permission(struct user_namespace *mnt_userns,
struct inode *inode, int mask)
{
struct inode *upperinode = ovl_inode_upper(inode);
struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
const struct cred *old_cred;
int err;
/* Careful in RCU walk mode */
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
return -ECHILD;
}
/*
* Check overlay inode with the creds of task and underlying inode
* with creds of mounter
*/
err = generic_permission(&init_user_ns, inode, mask);
if (err)
return err;
old_cred = ovl_override_creds(inode->i_sb);
if (!upperinode &&
!special_file(realinode->i_mode) && mask & MAY_WRITE) {
mask &= ~(MAY_WRITE | MAY_APPEND);
/* Make sure mounter can read file for copy up later */
mask |= MAY_READ;
}
err = inode_permission(&init_user_ns, realinode, mask);
revert_creds(old_cred);
return err;
}
static const char *ovl_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
const struct cred *old_cred;
const char *p;
if (!dentry)
return ERR_PTR(-ECHILD);
old_cred = ovl_override_creds(dentry->d_sb);
p = vfs_get_link(ovl_dentry_real(dentry), done);
revert_creds(old_cred);
return p;
}
bool ovl_is_private_xattr(struct super_block *sb, const char *name)
{
struct ovl_fs *ofs = sb->s_fs_info;
if (ofs->config.userxattr)
return strncmp(name, OVL_XATTR_USER_PREFIX,
sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
else
return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
}
int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
int err;
struct dentry *upperdentry = ovl_i_dentry_upper(inode);
struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
const struct cred *old_cred;
err = ovl_want_write(dentry);
if (err)
goto out;
if (!value && !upperdentry) {
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getxattr(&init_user_ns, realdentry, name, NULL, 0);
revert_creds(old_cred);
if (err < 0)
goto out_drop_write;
}
if (!upperdentry) {
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
realdentry = ovl_dentry_upper(dentry);
}
old_cred = ovl_override_creds(dentry->d_sb);
if (value)
err = vfs_setxattr(&init_user_ns, realdentry, name, value, size,
flags);
else {
WARN_ON(flags != XATTR_REPLACE);
err = vfs_removexattr(&init_user_ns, realdentry, name);
}
revert_creds(old_cred);
/* copy c/mtime */
ovl_copyattr(d_inode(realdentry), inode);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
void *value, size_t size)
{
ssize_t res;
const struct cred *old_cred;
struct dentry *realdentry =
ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_getxattr(&init_user_ns, realdentry, name, value, size);
revert_creds(old_cred);
return res;
}
static bool ovl_can_list(struct super_block *sb, const char *s)
{
/* Never list private (.overlay) */
if (ovl_is_private_xattr(sb, s))
return false;
/* List all non-trusted xattrs */
if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
return true;
/* list other trusted for superuser only */
return ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
size_t len;
char *s;
const struct cred *old_cred;
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_listxattr(realdentry, list, size);
revert_creds(old_cred);
if (res <= 0 || size == 0)
return res;
/* filter out private xattrs */
for (s = list, len = res; len;) {
size_t slen = strnlen(s, len) + 1;
/* underlying fs providing us with an broken xattr list? */
if (WARN_ON(slen > len))
return -EIO;
len -= slen;
if (!ovl_can_list(dentry->d_sb, s)) {
res -= slen;
memmove(s, s + slen, len);
} else {
s += slen;
}
}
return res;
}
struct posix_acl *ovl_get_acl(struct inode *inode, int type)
{
struct inode *realinode = ovl_inode_real(inode);
const struct cred *old_cred;
struct posix_acl *acl;
if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
return NULL;
old_cred = ovl_override_creds(inode->i_sb);
acl = get_acl(realinode, type);
revert_creds(old_cred);
return acl;
}
int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
{
if (flags & S_ATIME) {
struct ovl_fs *ofs = inode->i_sb->s_fs_info;
struct path upperpath = {
.mnt = ovl_upper_mnt(ofs),
.dentry = ovl_upperdentry_dereference(OVL_I(inode)),
};
if (upperpath.dentry) {
touch_atime(&upperpath);
inode->i_atime = d_inode(upperpath.dentry)->i_atime;
}
}
return 0;
}
static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
int err;
struct inode *realinode = ovl_inode_realdata(inode);
const struct cred *old_cred;
if (!realinode->i_op->fiemap)
return -EOPNOTSUPP;
old_cred = ovl_override_creds(inode->i_sb);
err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
revert_creds(old_cred);
return err;
}
/*
* Work around the fact that security_file_ioctl() takes a file argument.
* Introducing security_inode_fileattr_get/set() hooks would solve this issue
* properly.
*/
static int ovl_security_fileattr(struct path *realpath, struct fileattr *fa,
bool set)
{
struct file *file;
unsigned int cmd;
int err;
file = dentry_open(realpath, O_RDONLY, current_cred());
if (IS_ERR(file))
return PTR_ERR(file);
if (set)
cmd = fa->fsx_valid ? FS_IOC_FSSETXATTR : FS_IOC_SETFLAGS;
else
cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
err = security_file_ioctl(file, cmd, 0);
fput(file);
return err;
}
int ovl_real_fileattr_set(struct path *realpath, struct fileattr *fa)
{
int err;
err = ovl_security_fileattr(realpath, fa, true);
if (err)
return err;
return vfs_fileattr_set(&init_user_ns, realpath->dentry, fa);
}
int ovl_fileattr_set(struct user_namespace *mnt_userns,
struct dentry *dentry, struct fileattr *fa)
{
struct inode *inode = d_inode(dentry);
struct path upperpath;
const struct cred *old_cred;
int err;
err = ovl_want_write(dentry);
if (err)
goto out;
err = ovl_copy_up(dentry);
if (!err) {
ovl_path_real(dentry, &upperpath);
old_cred = ovl_override_creds(inode->i_sb);
err = ovl_real_fileattr_set(&upperpath, fa);
revert_creds(old_cred);
ovl_copyflags(ovl_inode_real(inode), inode);
}
ovl_drop_write(dentry);
out:
return err;
}
int ovl_real_fileattr_get(struct path *realpath, struct fileattr *fa)
{
int err;
err = ovl_security_fileattr(realpath, fa, false);
if (err)
return err;
return vfs_fileattr_get(realpath->dentry, fa);
}
int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)
{
struct inode *inode = d_inode(dentry);
struct path realpath;
const struct cred *old_cred;
int err;
ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(inode->i_sb);
err = ovl_real_fileattr_get(&realpath, fa);
revert_creds(old_cred);
return err;
}
static const struct inode_operations ovl_file_inode_operations = {
.setattr = ovl_setattr,
.permission = ovl_permission,
.getattr = ovl_getattr,
.listxattr = ovl_listxattr,
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
.fiemap = ovl_fiemap,
.fileattr_get = ovl_fileattr_get,
.fileattr_set = ovl_fileattr_set,
};
static const struct inode_operations ovl_symlink_inode_operations = {
.setattr = ovl_setattr,
.get_link = ovl_get_link,
.getattr = ovl_getattr,
.listxattr = ovl_listxattr,
.update_time = ovl_update_time,
};
static const struct inode_operations ovl_special_inode_operations = {
.setattr = ovl_setattr,
.permission = ovl_permission,
.getattr = ovl_getattr,
.listxattr = ovl_listxattr,
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
};
static const struct address_space_operations ovl_aops = {
/* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
.direct_IO = noop_direct_IO,
};
/*
* It is possible to stack overlayfs instance on top of another
* overlayfs instance as lower layer. We need to annotate the
* stackable i_mutex locks according to stack level of the super
* block instance. An overlayfs instance can never be in stack
* depth 0 (there is always a real fs below it). An overlayfs
* inode lock will use the lockdep annotation ovl_i_mutex_key[depth].
*
* For example, here is a snip from /proc/lockdep_chains after
* dir_iterate of nested overlayfs:
*
* [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
* [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
* [...] &type->i_mutex_dir_key (stack_depth=0)
*
* Locking order w.r.t ovl_want_write() is important for nested overlayfs.
*
* This chain is valid:
* - inode->i_rwsem (inode_lock[2])
* - upper_mnt->mnt_sb->s_writers (ovl_want_write[0])
* - OVL_I(inode)->lock (ovl_inode_lock[2])
* - OVL_I(lowerinode)->lock (ovl_inode_lock[1])
*
* And this chain is valid:
* - inode->i_rwsem (inode_lock[2])
* - OVL_I(inode)->lock (ovl_inode_lock[2])
* - lowerinode->i_rwsem (inode_lock[1])
* - OVL_I(lowerinode)->lock (ovl_inode_lock[1])
*
* But lowerinode->i_rwsem SHOULD NOT be acquired while ovl_want_write() is
* held, because it is in reverse order of the non-nested case using the same
* upper fs:
* - inode->i_rwsem (inode_lock[1])
* - upper_mnt->mnt_sb->s_writers (ovl_want_write[0])
* - OVL_I(inode)->lock (ovl_inode_lock[1])
*/
#define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
{
#ifdef CONFIG_LOCKDEP
static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
static struct lock_class_key ovl_i_lock_key[OVL_MAX_NESTING];
int depth = inode->i_sb->s_stack_depth - 1;
if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
depth = 0;
if (S_ISDIR(inode->i_mode))
lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
else
lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
lockdep_set_class(&OVL_I(inode)->lock, &ovl_i_lock_key[depth]);
#endif
}
static void ovl_next_ino(struct inode *inode)
{
struct ovl_fs *ofs = inode->i_sb->s_fs_info;
inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
if (unlikely(!inode->i_ino))
inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
}
static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
{
int xinobits = ovl_xino_bits(inode->i_sb);
unsigned int xinoshift = 64 - xinobits;
/*
* When d_ino is consistent with st_ino (samefs or i_ino has enough
* bits to encode layer), set the same value used for st_ino to i_ino,
* so inode number exposed via /proc/locks and a like will be
* consistent with d_ino and st_ino values. An i_ino value inconsistent
* with d_ino also causes nfsd readdirplus to fail.
*/
inode->i_ino = ino;
if (ovl_same_fs(inode->i_sb)) {
return;
} else if (xinobits && likely(!(ino >> xinoshift))) {
inode->i_ino |= (unsigned long)fsid << (xinoshift + 1);
return;
}
/*
* For directory inodes on non-samefs with xino disabled or xino
* overflow, we allocate a non-persistent inode number, to be used for
* resolving st_ino collisions in ovl_map_dev_ino().
*
* To avoid ino collision with legitimate xino values from upper
* layer (fsid 0), use the lowest xinobit to map the non
* persistent inode numbers to the unified st_ino address space.
*/
if (S_ISDIR(inode->i_mode)) {
ovl_next_ino(inode);
if (xinobits) {
inode->i_ino &= ~0UL >> xinobits;
inode->i_ino |= 1UL << xinoshift;
}
}
}
void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
unsigned long ino, int fsid)
{
struct inode *realinode;
if (oip->upperdentry)
OVL_I(inode)->__upperdentry = oip->upperdentry;
if (oip->lowerpath && oip->lowerpath->dentry)
OVL_I(inode)->lower = igrab(d_inode(oip->lowerpath->dentry));
if (oip->lowerdata)
OVL_I(inode)->lowerdata = igrab(d_inode(oip->lowerdata));
realinode = ovl_inode_real(inode);
ovl_copyattr(realinode, inode);
ovl_copyflags(realinode, inode);
ovl_map_ino(inode, ino, fsid);
}
static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
{
inode->i_mode = mode;
inode->i_flags |= S_NOCMTIME;
#ifdef CONFIG_FS_POSIX_ACL
inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
#endif
ovl_lockdep_annotate_inode_mutex_key(inode);
switch (mode & S_IFMT) {
case S_IFREG:
inode->i_op = &ovl_file_inode_operations;
inode->i_fop = &ovl_file_operations;
inode->i_mapping->a_ops = &ovl_aops;
break;
case S_IFDIR:
inode->i_op = &ovl_dir_inode_operations;
inode->i_fop = &ovl_dir_operations;
break;
case S_IFLNK:
inode->i_op = &ovl_symlink_inode_operations;
break;
default:
inode->i_op = &ovl_special_inode_operations;
init_special_inode(inode, mode, rdev);
break;
}
}
/*
* With inodes index enabled, an overlay inode nlink counts the union of upper
* hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
* upper inode, the following nlink modifying operations can happen:
*
* 1. Lower hardlink copy up
* 2. Upper hardlink created, unlinked or renamed over
* 3. Lower hardlink whiteout or renamed over
*
* For the first, copy up case, the union nlink does not change, whether the
* operation succeeds or fails, but the upper inode nlink may change.
* Therefore, before copy up, we store the union nlink value relative to the
* lower inode nlink in the index inode xattr .overlay.nlink.
*
* For the second, upper hardlink case, the union nlink should be incremented
* or decremented IFF the operation succeeds, aligned with nlink change of the
* upper inode. Therefore, before link/unlink/rename, we store the union nlink
* value relative to the upper inode nlink in the index inode.
*
* For the last, lower cover up case, we simplify things by preceding the
* whiteout or cover up with copy up. This makes sure that there is an index
* upper inode where the nlink xattr can be stored before the copied up upper
* entry is unlink.
*/
#define OVL_NLINK_ADD_UPPER (1 << 0)
/*
* On-disk format for indexed nlink:
*
* nlink relative to the upper inode - "U[+-]NUM"
* nlink relative to the lower inode - "L[+-]NUM"
*/
static int ovl_set_nlink_common(struct dentry *dentry,
struct dentry *realdentry, const char *format)
{
struct inode *inode = d_inode(dentry);
struct inode *realinode = d_inode(realdentry);
char buf[13];
int len;
len = snprintf(buf, sizeof(buf), format,
(int) (inode->i_nlink - realinode->i_nlink));
if (WARN_ON(len >= sizeof(buf)))
return -EIO;
return ovl_do_setxattr(OVL_FS(inode->i_sb), ovl_dentry_upper(dentry),
OVL_XATTR_NLINK, buf, len);
}
int ovl_set_nlink_upper(struct dentry *dentry)
{
return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i");
}
int ovl_set_nlink_lower(struct dentry *dentry)
{
return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
}
unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
struct dentry *upperdentry,
unsigned int fallback)
{
int nlink_diff;
int nlink;
char buf[13];
int err;
if (!lowerdentry || !upperdentry || d_inode(lowerdentry)->i_nlink == 1)
return fallback;
err = ovl_do_getxattr(ofs, upperdentry, OVL_XATTR_NLINK,
&buf, sizeof(buf) - 1);
if (err < 0)
goto fail;
buf[err] = '\0';
if ((buf[0] != 'L' && buf[0] != 'U') ||
(buf[1] != '+' && buf[1] != '-'))
goto fail;
err = kstrtoint(buf + 1, 10, &nlink_diff);
if (err < 0)
goto fail;
nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink;
nlink += nlink_diff;
if (nlink <= 0)
goto fail;
return nlink;
fail:
pr_warn_ratelimited("failed to get index nlink (%pd2, err=%i)\n",
upperdentry, err);
return fallback;
}
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
{
struct inode *inode;
inode = new_inode(sb);
if (inode)
ovl_fill_inode(inode, mode, rdev);
return inode;
}
static int ovl_inode_test(struct inode *inode, void *data)
{
return inode->i_private == data;
}
static int ovl_inode_set(struct inode *inode, void *data)
{
inode->i_private = data;
return 0;
}
static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
struct dentry *upperdentry, bool strict)
{
/*
* For directories, @strict verify from lookup path performs consistency
* checks, so NULL lower/upper in dentry must match NULL lower/upper in
* inode. Non @strict verify from NFS handle decode path passes NULL for
* 'unknown' lower/upper.
*/
if (S_ISDIR(inode->i_mode) && strict) {
/* Real lower dir moved to upper layer under us? */
if (!lowerdentry && ovl_inode_lower(inode))
return false;
/* Lookup of an uncovered redirect origin? */
if (!upperdentry && ovl_inode_upper(inode))
return false;
}
/*
* Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL.
* This happens when finding a copied up overlay inode for a renamed
* or hardlinked overlay dentry and lower dentry cannot be followed
* by origin because lower fs does not support file handles.
*/
if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry))
return false;
/*
* Allow non-NULL __upperdentry in inode even if upperdentry is NULL.
* This happens when finding a lower alias for a copied up hard link.
*/
if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry))
return false;
return true;
}
struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
bool is_upper)
{
struct inode *inode, *key = d_inode(real);
inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
if (!inode)
return NULL;
if (!ovl_verify_inode(inode, is_upper ? NULL : real,
is_upper ? real : NULL, false)) {
iput(inode);
return ERR_PTR(-ESTALE);
}
return inode;
}
bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
{
struct inode *key = d_inode(dir);
struct inode *trap;
bool res;
trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
if (!trap)
return false;
res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
!ovl_inode_lower(trap);
iput(trap);
return res;
}
/*
* Create an inode cache entry for layer root dir, that will intentionally
* fail ovl_verify_inode(), so any lookup that will find some layer root
* will fail.
*/
struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
{
struct inode *key = d_inode(dir);
struct inode *trap;
if (!d_is_dir(dir))
return ERR_PTR(-ENOTDIR);
trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
ovl_inode_set, key);
if (!trap)
return ERR_PTR(-ENOMEM);
if (!(trap->i_state & I_NEW)) {
/* Conflicting layer roots? */
iput(trap);
return ERR_PTR(-ELOOP);