forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
586 lines
15 KiB
586 lines
15 KiB
// SPDX-License-Identifier: GPL-2.0-only |
|
/* |
|
* Copyright (C) Neil Brown 2002 |
|
* Copyright (C) Christoph Hellwig 2007 |
|
* |
|
* This file contains the code mapping from inodes to NFS file handles, |
|
* and for mapping back from file handles to dentries. |
|
* |
|
* For details on why we do all the strange and hairy things in here |
|
* take a look at Documentation/filesystems/nfs/exporting.rst. |
|
*/ |
|
#include <linux/exportfs.h> |
|
#include <linux/fs.h> |
|
#include <linux/file.h> |
|
#include <linux/module.h> |
|
#include <linux/mount.h> |
|
#include <linux/namei.h> |
|
#include <linux/sched.h> |
|
#include <linux/cred.h> |
|
|
|
#define dprintk(fmt, args...) do{}while(0) |
|
|
|
|
|
static int get_name(const struct path *path, char *name, struct dentry *child); |
|
|
|
|
|
static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir, |
|
char *name, struct dentry *child) |
|
{ |
|
const struct export_operations *nop = dir->d_sb->s_export_op; |
|
struct path path = {.mnt = mnt, .dentry = dir}; |
|
|
|
if (nop->get_name) |
|
return nop->get_name(dir, name, child); |
|
else |
|
return get_name(&path, name, child); |
|
} |
|
|
|
/* |
|
* Check if the dentry or any of it's aliases is acceptable. |
|
*/ |
|
static struct dentry * |
|
find_acceptable_alias(struct dentry *result, |
|
int (*acceptable)(void *context, struct dentry *dentry), |
|
void *context) |
|
{ |
|
struct dentry *dentry, *toput = NULL; |
|
struct inode *inode; |
|
|
|
if (acceptable(context, result)) |
|
return result; |
|
|
|
inode = result->d_inode; |
|
spin_lock(&inode->i_lock); |
|
hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) { |
|
dget(dentry); |
|
spin_unlock(&inode->i_lock); |
|
if (toput) |
|
dput(toput); |
|
if (dentry != result && acceptable(context, dentry)) { |
|
dput(result); |
|
return dentry; |
|
} |
|
spin_lock(&inode->i_lock); |
|
toput = dentry; |
|
} |
|
spin_unlock(&inode->i_lock); |
|
|
|
if (toput) |
|
dput(toput); |
|
return NULL; |
|
} |
|
|
|
static bool dentry_connected(struct dentry *dentry) |
|
{ |
|
dget(dentry); |
|
while (dentry->d_flags & DCACHE_DISCONNECTED) { |
|
struct dentry *parent = dget_parent(dentry); |
|
|
|
dput(dentry); |
|
if (dentry == parent) { |
|
dput(parent); |
|
return false; |
|
} |
|
dentry = parent; |
|
} |
|
dput(dentry); |
|
return true; |
|
} |
|
|
|
static void clear_disconnected(struct dentry *dentry) |
|
{ |
|
dget(dentry); |
|
while (dentry->d_flags & DCACHE_DISCONNECTED) { |
|
struct dentry *parent = dget_parent(dentry); |
|
|
|
WARN_ON_ONCE(IS_ROOT(dentry)); |
|
|
|
spin_lock(&dentry->d_lock); |
|
dentry->d_flags &= ~DCACHE_DISCONNECTED; |
|
spin_unlock(&dentry->d_lock); |
|
|
|
dput(dentry); |
|
dentry = parent; |
|
} |
|
dput(dentry); |
|
} |
|
|
|
/* |
|
* Reconnect a directory dentry with its parent. |
|
* |
|
* This can return a dentry, or NULL, or an error. |
|
* |
|
* In the first case the returned dentry is the parent of the given |
|
* dentry, and may itself need to be reconnected to its parent. |
|
* |
|
* In the NULL case, a concurrent VFS operation has either renamed or |
|
* removed this directory. The concurrent operation has reconnected our |
|
* dentry, so we no longer need to. |
|
*/ |
|
static struct dentry *reconnect_one(struct vfsmount *mnt, |
|
struct dentry *dentry, char *nbuf) |
|
{ |
|
struct dentry *parent; |
|
struct dentry *tmp; |
|
int err; |
|
|
|
parent = ERR_PTR(-EACCES); |
|
inode_lock(dentry->d_inode); |
|
if (mnt->mnt_sb->s_export_op->get_parent) |
|
parent = mnt->mnt_sb->s_export_op->get_parent(dentry); |
|
inode_unlock(dentry->d_inode); |
|
|
|
if (IS_ERR(parent)) { |
|
dprintk("%s: get_parent of %ld failed, err %d\n", |
|
__func__, dentry->d_inode->i_ino, PTR_ERR(parent)); |
|
return parent; |
|
} |
|
|
|
dprintk("%s: find name of %lu in %lu\n", __func__, |
|
dentry->d_inode->i_ino, parent->d_inode->i_ino); |
|
err = exportfs_get_name(mnt, parent, nbuf, dentry); |
|
if (err == -ENOENT) |
|
goto out_reconnected; |
|
if (err) |
|
goto out_err; |
|
dprintk("%s: found name: %s\n", __func__, nbuf); |
|
tmp = lookup_one_len_unlocked(nbuf, parent, strlen(nbuf)); |
|
if (IS_ERR(tmp)) { |
|
dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp)); |
|
err = PTR_ERR(tmp); |
|
goto out_err; |
|
} |
|
if (tmp != dentry) { |
|
/* |
|
* Somebody has renamed it since exportfs_get_name(); |
|
* great, since it could've only been renamed if it |
|
* got looked up and thus connected, and it would |
|
* remain connected afterwards. We are done. |
|
*/ |
|
dput(tmp); |
|
goto out_reconnected; |
|
} |
|
dput(tmp); |
|
if (IS_ROOT(dentry)) { |
|
err = -ESTALE; |
|
goto out_err; |
|
} |
|
return parent; |
|
|
|
out_err: |
|
dput(parent); |
|
return ERR_PTR(err); |
|
out_reconnected: |
|
dput(parent); |
|
/* |
|
* Someone must have renamed our entry into another parent, in |
|
* which case it has been reconnected by the rename. |
|
* |
|
* Or someone removed it entirely, in which case filehandle |
|
* lookup will succeed but the directory is now IS_DEAD and |
|
* subsequent operations on it will fail. |
|
* |
|
* Alternatively, maybe there was no race at all, and the |
|
* filesystem is just corrupt and gave us a parent that doesn't |
|
* actually contain any entry pointing to this inode. So, |
|
* double check that this worked and return -ESTALE if not: |
|
*/ |
|
if (!dentry_connected(dentry)) |
|
return ERR_PTR(-ESTALE); |
|
return NULL; |
|
} |
|
|
|
/* |
|
* Make sure target_dir is fully connected to the dentry tree. |
|
* |
|
* On successful return, DCACHE_DISCONNECTED will be cleared on |
|
* target_dir, and target_dir->d_parent->...->d_parent will reach the |
|
* root of the filesystem. |
|
* |
|
* Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected. |
|
* But the converse is not true: target_dir may have DCACHE_DISCONNECTED |
|
* set but already be connected. In that case we'll verify the |
|
* connection to root and then clear the flag. |
|
* |
|
* Note that target_dir could be removed by a concurrent operation. In |
|
* that case reconnect_path may still succeed with target_dir fully |
|
* connected, but further operations using the filehandle will fail when |
|
* necessary (due to S_DEAD being set on the directory). |
|
*/ |
|
static int |
|
reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf) |
|
{ |
|
struct dentry *dentry, *parent; |
|
|
|
dentry = dget(target_dir); |
|
|
|
while (dentry->d_flags & DCACHE_DISCONNECTED) { |
|
BUG_ON(dentry == mnt->mnt_sb->s_root); |
|
|
|
if (IS_ROOT(dentry)) |
|
parent = reconnect_one(mnt, dentry, nbuf); |
|
else |
|
parent = dget_parent(dentry); |
|
|
|
if (!parent) |
|
break; |
|
dput(dentry); |
|
if (IS_ERR(parent)) |
|
return PTR_ERR(parent); |
|
dentry = parent; |
|
} |
|
dput(dentry); |
|
clear_disconnected(target_dir); |
|
return 0; |
|
} |
|
|
|
struct getdents_callback { |
|
struct dir_context ctx; |
|
char *name; /* name that was found. It already points to a |
|
buffer NAME_MAX+1 is size */ |
|
u64 ino; /* the inum we are looking for */ |
|
int found; /* inode matched? */ |
|
int sequence; /* sequence counter */ |
|
}; |
|
|
|
/* |
|
* A rather strange filldir function to capture |
|
* the name matching the specified inode number. |
|
*/ |
|
static int filldir_one(struct dir_context *ctx, const char *name, int len, |
|
loff_t pos, u64 ino, unsigned int d_type) |
|
{ |
|
struct getdents_callback *buf = |
|
container_of(ctx, struct getdents_callback, ctx); |
|
int result = 0; |
|
|
|
buf->sequence++; |
|
if (buf->ino == ino && len <= NAME_MAX) { |
|
memcpy(buf->name, name, len); |
|
buf->name[len] = '\0'; |
|
buf->found = 1; |
|
result = -1; |
|
} |
|
return result; |
|
} |
|
|
|
/** |
|
* get_name - default export_operations->get_name function |
|
* @path: the directory in which to find a name |
|
* @name: a pointer to a %NAME_MAX+1 char buffer to store the name |
|
* @child: the dentry for the child directory. |
|
* |
|
* calls readdir on the parent until it finds an entry with |
|
* the same inode number as the child, and returns that. |
|
*/ |
|
static int get_name(const struct path *path, char *name, struct dentry *child) |
|
{ |
|
const struct cred *cred = current_cred(); |
|
struct inode *dir = path->dentry->d_inode; |
|
int error; |
|
struct file *file; |
|
struct kstat stat; |
|
struct path child_path = { |
|
.mnt = path->mnt, |
|
.dentry = child, |
|
}; |
|
struct getdents_callback buffer = { |
|
.ctx.actor = filldir_one, |
|
.name = name, |
|
}; |
|
|
|
error = -ENOTDIR; |
|
if (!dir || !S_ISDIR(dir->i_mode)) |
|
goto out; |
|
error = -EINVAL; |
|
if (!dir->i_fop) |
|
goto out; |
|
/* |
|
* inode->i_ino is unsigned long, kstat->ino is u64, so the |
|
* former would be insufficient on 32-bit hosts when the |
|
* filesystem supports 64-bit inode numbers. So we need to |
|
* actually call ->getattr, not just read i_ino: |
|
*/ |
|
error = vfs_getattr_nosec(&child_path, &stat, |
|
STATX_INO, AT_STATX_SYNC_AS_STAT); |
|
if (error) |
|
return error; |
|
buffer.ino = stat.ino; |
|
/* |
|
* Open the directory ... |
|
*/ |
|
file = dentry_open(path, O_RDONLY, cred); |
|
error = PTR_ERR(file); |
|
if (IS_ERR(file)) |
|
goto out; |
|
|
|
error = -EINVAL; |
|
if (!file->f_op->iterate && !file->f_op->iterate_shared) |
|
goto out_close; |
|
|
|
buffer.sequence = 0; |
|
while (1) { |
|
int old_seq = buffer.sequence; |
|
|
|
error = iterate_dir(file, &buffer.ctx); |
|
if (buffer.found) { |
|
error = 0; |
|
break; |
|
} |
|
|
|
if (error < 0) |
|
break; |
|
|
|
error = -ENOENT; |
|
if (old_seq == buffer.sequence) |
|
break; |
|
} |
|
|
|
out_close: |
|
fput(file); |
|
out: |
|
return error; |
|
} |
|
|
|
/** |
|
* export_encode_fh - default export_operations->encode_fh function |
|
* @inode: the object to encode |
|
* @fid: where to store the file handle fragment |
|
* @max_len: maximum length to store there |
|
* @parent: parent directory inode, if wanted |
|
* |
|
* This default encode_fh function assumes that the 32 inode number |
|
* is suitable for locating an inode, and that the generation number |
|
* can be used to check that it is still valid. It places them in the |
|
* filehandle fragment where export_decode_fh expects to find them. |
|
*/ |
|
static int export_encode_fh(struct inode *inode, struct fid *fid, |
|
int *max_len, struct inode *parent) |
|
{ |
|
int len = *max_len; |
|
int type = FILEID_INO32_GEN; |
|
|
|
if (parent && (len < 4)) { |
|
*max_len = 4; |
|
return FILEID_INVALID; |
|
} else if (len < 2) { |
|
*max_len = 2; |
|
return FILEID_INVALID; |
|
} |
|
|
|
len = 2; |
|
fid->i32.ino = inode->i_ino; |
|
fid->i32.gen = inode->i_generation; |
|
if (parent) { |
|
fid->i32.parent_ino = parent->i_ino; |
|
fid->i32.parent_gen = parent->i_generation; |
|
len = 4; |
|
type = FILEID_INO32_GEN_PARENT; |
|
} |
|
*max_len = len; |
|
return type; |
|
} |
|
|
|
int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid, |
|
int *max_len, struct inode *parent) |
|
{ |
|
const struct export_operations *nop = inode->i_sb->s_export_op; |
|
|
|
if (nop && nop->encode_fh) |
|
return nop->encode_fh(inode, fid->raw, max_len, parent); |
|
|
|
return export_encode_fh(inode, fid, max_len, parent); |
|
} |
|
EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh); |
|
|
|
int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len, |
|
int connectable) |
|
{ |
|
int error; |
|
struct dentry *p = NULL; |
|
struct inode *inode = dentry->d_inode, *parent = NULL; |
|
|
|
if (connectable && !S_ISDIR(inode->i_mode)) { |
|
p = dget_parent(dentry); |
|
/* |
|
* note that while p might've ceased to be our parent already, |
|
* it's still pinned by and still positive. |
|
*/ |
|
parent = p->d_inode; |
|
} |
|
|
|
error = exportfs_encode_inode_fh(inode, fid, max_len, parent); |
|
dput(p); |
|
|
|
return error; |
|
} |
|
EXPORT_SYMBOL_GPL(exportfs_encode_fh); |
|
|
|
struct dentry * |
|
exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len, |
|
int fileid_type, |
|
int (*acceptable)(void *, struct dentry *), |
|
void *context) |
|
{ |
|
const struct export_operations *nop = mnt->mnt_sb->s_export_op; |
|
struct dentry *result, *alias; |
|
char nbuf[NAME_MAX+1]; |
|
int err; |
|
|
|
/* |
|
* Try to get any dentry for the given file handle from the filesystem. |
|
*/ |
|
if (!nop || !nop->fh_to_dentry) |
|
return ERR_PTR(-ESTALE); |
|
result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type); |
|
if (IS_ERR_OR_NULL(result)) |
|
return result; |
|
|
|
/* |
|
* If no acceptance criteria was specified by caller, a disconnected |
|
* dentry is also accepatable. Callers may use this mode to query if |
|
* file handle is stale or to get a reference to an inode without |
|
* risking the high overhead caused by directory reconnect. |
|
*/ |
|
if (!acceptable) |
|
return result; |
|
|
|
if (d_is_dir(result)) { |
|
/* |
|
* This request is for a directory. |
|
* |
|
* On the positive side there is only one dentry for each |
|
* directory inode. On the negative side this implies that we |
|
* to ensure our dentry is connected all the way up to the |
|
* filesystem root. |
|
*/ |
|
if (result->d_flags & DCACHE_DISCONNECTED) { |
|
err = reconnect_path(mnt, result, nbuf); |
|
if (err) |
|
goto err_result; |
|
} |
|
|
|
if (!acceptable(context, result)) { |
|
err = -EACCES; |
|
goto err_result; |
|
} |
|
|
|
return result; |
|
} else { |
|
/* |
|
* It's not a directory. Life is a little more complicated. |
|
*/ |
|
struct dentry *target_dir, *nresult; |
|
|
|
/* |
|
* See if either the dentry we just got from the filesystem |
|
* or any alias for it is acceptable. This is always true |
|
* if this filesystem is exported without the subtreecheck |
|
* option. If the filesystem is exported with the subtree |
|
* check option there's a fair chance we need to look at |
|
* the parent directory in the file handle and make sure |
|
* it's connected to the filesystem root. |
|
*/ |
|
alias = find_acceptable_alias(result, acceptable, context); |
|
if (alias) |
|
return alias; |
|
|
|
/* |
|
* Try to extract a dentry for the parent directory from the |
|
* file handle. If this fails we'll have to give up. |
|
*/ |
|
err = -ESTALE; |
|
if (!nop->fh_to_parent) |
|
goto err_result; |
|
|
|
target_dir = nop->fh_to_parent(mnt->mnt_sb, fid, |
|
fh_len, fileid_type); |
|
if (!target_dir) |
|
goto err_result; |
|
err = PTR_ERR(target_dir); |
|
if (IS_ERR(target_dir)) |
|
goto err_result; |
|
|
|
/* |
|
* And as usual we need to make sure the parent directory is |
|
* connected to the filesystem root. The VFS really doesn't |
|
* like disconnected directories.. |
|
*/ |
|
err = reconnect_path(mnt, target_dir, nbuf); |
|
if (err) { |
|
dput(target_dir); |
|
goto err_result; |
|
} |
|
|
|
/* |
|
* Now that we've got both a well-connected parent and a |
|
* dentry for the inode we're after, make sure that our |
|
* inode is actually connected to the parent. |
|
*/ |
|
err = exportfs_get_name(mnt, target_dir, nbuf, result); |
|
if (err) { |
|
dput(target_dir); |
|
goto err_result; |
|
} |
|
|
|
inode_lock(target_dir->d_inode); |
|
nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf)); |
|
if (!IS_ERR(nresult)) { |
|
if (unlikely(nresult->d_inode != result->d_inode)) { |
|
dput(nresult); |
|
nresult = ERR_PTR(-ESTALE); |
|
} |
|
} |
|
inode_unlock(target_dir->d_inode); |
|
/* |
|
* At this point we are done with the parent, but it's pinned |
|
* by the child dentry anyway. |
|
*/ |
|
dput(target_dir); |
|
|
|
if (IS_ERR(nresult)) { |
|
err = PTR_ERR(nresult); |
|
goto err_result; |
|
} |
|
dput(result); |
|
result = nresult; |
|
|
|
/* |
|
* And finally make sure the dentry is actually acceptable |
|
* to NFSD. |
|
*/ |
|
alias = find_acceptable_alias(result, acceptable, context); |
|
if (!alias) { |
|
err = -EACCES; |
|
goto err_result; |
|
} |
|
|
|
return alias; |
|
} |
|
|
|
err_result: |
|
dput(result); |
|
return ERR_PTR(err); |
|
} |
|
EXPORT_SYMBOL_GPL(exportfs_decode_fh_raw); |
|
|
|
struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, |
|
int fh_len, int fileid_type, |
|
int (*acceptable)(void *, struct dentry *), |
|
void *context) |
|
{ |
|
struct dentry *ret; |
|
|
|
ret = exportfs_decode_fh_raw(mnt, fid, fh_len, fileid_type, |
|
acceptable, context); |
|
if (IS_ERR_OR_NULL(ret)) { |
|
if (ret == ERR_PTR(-ENOMEM)) |
|
return ret; |
|
return ERR_PTR(-ESTALE); |
|
} |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(exportfs_decode_fh); |
|
|
|
MODULE_LICENSE("GPL");
|
|
|