linux/fs/nfs/namespace.c
Christian Brauner b74d24f7a7
fs: port ->getattr() to pass mnt_idmap
Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2023-01-19 09:24:25 +01:00

370 lines
9.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/nfs/namespace.c
*
* Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
* - Modified by David Howells <dhowells@redhat.com>
*
* NFS namespace
*/
#include <linux/module.h>
#include <linux/dcache.h>
#include <linux/gfp.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nfs_fs.h>
#include <linux/string.h>
#include <linux/sunrpc/clnt.h>
#include <linux/vfs.h>
#include <linux/sunrpc/gss_api.h>
#include "internal.h"
#include "nfs.h"
#define NFSDBG_FACILITY NFSDBG_VFS
static void nfs_expire_automounts(struct work_struct *work);
static LIST_HEAD(nfs_automount_list);
static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
int nfs_mountpoint_expiry_timeout = 500 * HZ;
/*
* nfs_path - reconstruct the path given an arbitrary dentry
* @base - used to return pointer to the end of devname part of path
* @dentry_in - pointer to dentry
* @buffer - result buffer
* @buflen_in - length of buffer
* @flags - options (see below)
*
* Helper function for constructing the server pathname
* by arbitrary hashed dentry.
*
* This is mainly for use in figuring out the path on the
* server side when automounting on top of an existing partition
* and in generating /proc/mounts and friends.
*
* Supported flags:
* NFS_PATH_CANONICAL: ensure there is exactly one slash after
* the original device (export) name
* (if unset, the original name is returned verbatim)
*/
char *nfs_path(char **p, struct dentry *dentry_in, char *buffer,
ssize_t buflen_in, unsigned flags)
{
char *end;
int namelen;
unsigned seq;
const char *base;
struct dentry *dentry;
ssize_t buflen;
rename_retry:
buflen = buflen_in;
dentry = dentry_in;
end = buffer+buflen;
*--end = '\0';
buflen--;
seq = read_seqbegin(&rename_lock);
rcu_read_lock();
while (1) {
spin_lock(&dentry->d_lock);
if (IS_ROOT(dentry))
break;
namelen = dentry->d_name.len;
buflen -= namelen + 1;
if (buflen < 0)
goto Elong_unlock;
end -= namelen;
memcpy(end, dentry->d_name.name, namelen);
*--end = '/';
spin_unlock(&dentry->d_lock);
dentry = dentry->d_parent;
}
if (read_seqretry(&rename_lock, seq)) {
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
goto rename_retry;
}
if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
if (--buflen < 0) {
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
goto Elong;
}
*--end = '/';
}
*p = end;
base = dentry->d_fsdata;
if (!base) {
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
WARN_ON(1);
return end;
}
namelen = strlen(base);
if (*end == '/') {
/* Strip off excess slashes in base string */
while (namelen > 0 && base[namelen - 1] == '/')
namelen--;
}
buflen -= namelen;
if (buflen < 0) {
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
goto Elong;
}
end -= namelen;
memcpy(end, base, namelen);
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
return end;
Elong_unlock:
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
if (read_seqretry(&rename_lock, seq))
goto rename_retry;
Elong:
return ERR_PTR(-ENAMETOOLONG);
}
EXPORT_SYMBOL_GPL(nfs_path);
/*
* nfs_d_automount - Handle crossing a mountpoint on the server
* @path - The mountpoint
*
* When we encounter a mountpoint on the server, we want to set up
* a mountpoint on the client too, to prevent inode numbers from
* colliding, and to allow "df" to work properly.
* On NFSv4, we also want to allow for the fact that different
* filesystems may be migrated to different servers in a failover
* situation, and that different filesystems may want to use
* different security flavours.
*/
struct vfsmount *nfs_d_automount(struct path *path)
{
struct nfs_fs_context *ctx;
struct fs_context *fc;
struct vfsmount *mnt = ERR_PTR(-ENOMEM);
struct nfs_server *server = NFS_SB(path->dentry->d_sb);
struct nfs_client *client = server->nfs_client;
int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
int ret;
if (IS_ROOT(path->dentry))
return ERR_PTR(-ESTALE);
/* Open a new filesystem context, transferring parameters from the
* parent superblock, including the network namespace.
*/
fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
if (IS_ERR(fc))
return ERR_CAST(fc);
ctx = nfs_fc2context(fc);
ctx->clone_data.dentry = path->dentry;
ctx->clone_data.sb = path->dentry->d_sb;
ctx->clone_data.fattr = nfs_alloc_fattr();
if (!ctx->clone_data.fattr)
goto out_fc;
if (fc->net_ns != client->cl_net) {
put_net(fc->net_ns);
fc->net_ns = get_net(client->cl_net);
}
/* for submounts we want the same server; referrals will reassign */
memcpy(&ctx->nfs_server._address, &client->cl_addr, client->cl_addrlen);
ctx->nfs_server.addrlen = client->cl_addrlen;
ctx->nfs_server.port = server->port;
ctx->version = client->rpc_ops->version;
ctx->minorversion = client->cl_minorversion;
ctx->nfs_mod = client->cl_nfs_mod;
__module_get(ctx->nfs_mod->owner);
ret = client->rpc_ops->submount(fc, server);
if (ret < 0) {
mnt = ERR_PTR(ret);
goto out_fc;
}
up_write(&fc->root->d_sb->s_umount);
mnt = vfs_create_mount(fc);
if (IS_ERR(mnt))
goto out_fc;
mntget(mnt); /* prevent immediate expiration */
if (timeout <= 0)
goto out_fc;
mnt_set_expiry(mnt, &nfs_automount_list);
schedule_delayed_work(&nfs_automount_task, timeout);
out_fc:
put_fs_context(fc);
return mnt;
}
static int
nfs_namespace_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
if (NFS_FH(d_inode(path->dentry))->size != 0)
return nfs_getattr(idmap, path, stat, request_mask,
query_flags);
generic_fillattr(&nop_mnt_idmap, d_inode(path->dentry), stat);
return 0;
}
static int
nfs_namespace_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
struct iattr *attr)
{
if (NFS_FH(d_inode(dentry))->size != 0)
return nfs_setattr(idmap, dentry, attr);
return -EACCES;
}
const struct inode_operations nfs_mountpoint_inode_operations = {
.getattr = nfs_getattr,
.setattr = nfs_setattr,
};
const struct inode_operations nfs_referral_inode_operations = {
.getattr = nfs_namespace_getattr,
.setattr = nfs_namespace_setattr,
};
static void nfs_expire_automounts(struct work_struct *work)
{
struct list_head *list = &nfs_automount_list;
int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
mark_mounts_for_expiry(list);
if (!list_empty(list) && timeout > 0)
schedule_delayed_work(&nfs_automount_task, timeout);
}
void nfs_release_automount_timer(void)
{
if (list_empty(&nfs_automount_list))
cancel_delayed_work(&nfs_automount_task);
}
/**
* nfs_do_submount - set up mountpoint when crossing a filesystem boundary
* @fc: pointer to struct nfs_fs_context
*
*/
int nfs_do_submount(struct fs_context *fc)
{
struct nfs_fs_context *ctx = nfs_fc2context(fc);
struct dentry *dentry = ctx->clone_data.dentry;
struct nfs_server *server;
char *buffer, *p;
int ret;
/* create a new volume representation */
server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
ctx->mntfh,
ctx->clone_data.fattr,
ctx->selected_flavor);
if (IS_ERR(server))
return PTR_ERR(server);
ctx->server = server;
buffer = kmalloc(4096, GFP_USER);
if (!buffer)
return -ENOMEM;
ctx->internal = true;
ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits;
p = nfs_devname(dentry, buffer, 4096);
if (IS_ERR(p)) {
nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
ret = PTR_ERR(p);
} else {
ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
if (!ret)
ret = vfs_get_tree(fc);
}
kfree(buffer);
return ret;
}
EXPORT_SYMBOL_GPL(nfs_do_submount);
int nfs_submount(struct fs_context *fc, struct nfs_server *server)
{
struct nfs_fs_context *ctx = nfs_fc2context(fc);
struct dentry *dentry = ctx->clone_data.dentry;
struct dentry *parent = dget_parent(dentry);
int err;
/* Look it up again to get its attributes */
err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry,
ctx->mntfh, ctx->clone_data.fattr);
dput(parent);
if (err != 0)
return err;
ctx->selected_flavor = server->client->cl_auth->au_flavor;
return nfs_do_submount(fc);
}
EXPORT_SYMBOL_GPL(nfs_submount);
static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
{
long num;
int ret;
if (!val)
return -EINVAL;
ret = kstrtol(val, 0, &num);
if (ret)
return -EINVAL;
if (num > 0) {
if (num >= INT_MAX / HZ)
num = INT_MAX;
else
num *= HZ;
*((int *)kp->arg) = num;
if (!list_empty(&nfs_automount_list))
mod_delayed_work(system_wq, &nfs_automount_task, num);
} else {
*((int *)kp->arg) = -1*HZ;
cancel_delayed_work(&nfs_automount_task);
}
return 0;
}
static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp)
{
long num = *((int *)kp->arg);
if (num > 0) {
if (num >= INT_MAX - (HZ - 1))
num = INT_MAX / HZ;
else
num = (num + (HZ - 1)) / HZ;
} else
num = -1;
return sysfs_emit(buffer, "%li\n", num);
}
static const struct kernel_param_ops param_ops_nfs_timeout = {
.set = param_set_nfs_timeout,
.get = param_get_nfs_timeout,
};
#define param_check_nfs_timeout(name, p) __param_check(name, p, int)
module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
"Set the NFS automounted mountpoint timeout value (seconds)."
"Values <= 0 turn expiration off.");