// SPDX-License-Identifier: GPL-2.0
/*
* NFS server file handle treatment.
*
* Copyright (C) 1995, 1996 Olaf Kirch <[email protected]>
* Portions Copyright (C) 1999 G. Allen Morris III <[email protected]>
* Extensive rewrite by Neil Brown <[email protected]> Southern-Spring 1999
* ... and again Southern-Winter 2001 to support export_operations
*/
#include <linux/exportfs.h>
#include <linux/sunrpc/svcauth_gss.h>
#include "nfsd.h"
#include "vfs.h"
#include "auth.h"
#include "trace.h"
#define NFSDDBG_FACILITY NFSDDBG_FH
/*
* our acceptability function.
* if NOSUBTREECHECK, accept anything
* if not, require that we can walk up to exp->ex_dentry
* doing some checks on the 'x' bits
*/
static int nfsd_acceptable(void *expv, struct dentry *dentry)
{
struct svc_export *exp = expv;
int rv;
struct dentry *tdentry;
struct dentry *parent;
if (exp->ex_flags & NFSEXP_NOSUBTREECHECK)
return 1;
tdentry = dget(dentry);
while (tdentry != exp->ex_path.dentry && !IS_ROOT(tdentry)) {
/* make sure parents give x permission to user */
int err;
parent = dget_parent(tdentry);
err = inode_permission(&nop_mnt_idmap,
d_inode(parent), MAY_EXEC);
if (err < 0) {
dput(parent);
break;
}
dput(tdentry);
tdentry = parent;
}
if (tdentry != exp->ex_path.dentry)
dprintk("nfsd_acceptable failed at %p %pd\n", tdentry, tdentry);
rv = (tdentry == exp->ex_path.dentry);
dput(tdentry);
return rv;
}
/* Type check. The correct error return for type mismatches does not seem to be
* generally agreed upon. SunOS seems to use EISDIR if file isn't S_IFREG; a
* comment in the NFSv3 spec says this is incorrect (implementation notes for
* the write call).
*/
static inline __be32
nfsd_mode_check(struct dentry *dentry, umode_t requested)
{
umode_t mode = d_inode(dentry)->i_mode & S_IFMT;
if (requested == 0) /* the caller doesn't care */
return nfs_ok;
if (mode == requested) {
if (mode == S_IFDIR && !d_can_lookup(dentry)) {
WARN_ON_ONCE(1);
return nfserr_notdir;
}
return nfs_ok;
}
if (mode == S_IFLNK) {
if (requested == S_IFDIR)
return nfserr_symlink_not_dir;
return nfserr_symlink;
}
if (requested == S_IFDIR)
return nfserr_notdir;
if (mode == S_IFDIR)
return nfserr_isdir;
return nfserr_wrong_type;
}
static bool nfsd_originating_port_ok(struct svc_rqst *rqstp,
struct svc_cred *cred,
struct svc_export *exp)
{
if (nfsexp_flags(cred, exp) & NFSEXP_INSECURE_PORT)
return true;
/* We don't require gss requests to use low ports: */
if (cred->cr_flavor >= RPC_AUTH_GSS)
return true;
return test_bit(RQ_SECURE, &rqstp->rq_flags);
}
static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
struct svc_cred *cred,
struct svc_export *exp)
{
/* Check if the request originated from a secure port. */
if (rqstp && !nfsd_originating_port_ok(rqstp, cred, exp)) {
RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
dprintk("nfsd: request from insecure port %s!\n",
svc_print_addr(rqstp, buf, sizeof(buf)));
return nfserr_perm;
}
/* Set user creds for this exportpoint */
return nfserrno(nfsd_setuser(cred, exp));
}
static inline __be32 check_pseudo_root(struct dentry *dentry,
struct svc_export *exp)
{
if (!(exp->ex_flags & NFSEXP_V4ROOT))
return nfs_ok;
/*
* We're exposing only the directories and symlinks that have to be
* traversed on the way to real exports:
*/
if (unlikely(!d_is_dir(dentry) &&
!d_is_symlink(dentry)))
return nfserr_stale;
/*
* A pseudoroot export gives permission to access only one
* single directory; the kernel has to make another upcall
* before granting access to anything else under it:
*/
if (unlikely(dentry != exp->ex_path.dentry))
return nfserr_stale;
return nfs_ok;
}
/*
* Use the given filehandle to look up the corresponding export and
* dentry. On success, the results are used to set fh_export and
* fh_dentry.
*/
static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net,
struct svc_cred *cred,
struct auth_domain *client,
struct auth_domain *gssclient,
struct svc_fh *fhp)
{
struct knfsd_fh *fh = &fhp->fh_handle;
struct fid *fid = NULL;
struct svc_export *exp;
struct dentry *dentry;
int fileid_type;
int data_left = fh->fh_size/4;
int len;
__be32 error;
error = nfserr_badhandle;
if (fh->fh_size == 0)
return nfserr_nofilehandle;
if (fh->fh_version != 1)
return error;
if (--data_left < 0)
return error;
if (fh->fh_auth_type != 0)
return error;
len = key_len(fh->fh_fsid_type) / 4;
if (len == 0)
return error;
if (fh->fh_fsid_type == FSID_MAJOR_MINOR) {
/* deprecated, convert to type 3 */
len = key_len(FSID_ENCODE_DEV)/4;
fh->fh_fsid_type = FSID_ENCODE_DEV;
/*
* struct knfsd_fh uses host-endian fields, which are
* sometimes used to hold net-endian values. This
* confuses sparse, so we must use __force here to
* keep it from complaining.
*/
fh->fh_fsid[0] = new_encode_dev(MKDEV(ntohl((__force __be32)fh->fh_fsid[0]),
ntohl((__force __be32)fh->fh_fsid[1])));
fh->fh_fsid[1] = fh->fh_fsid[2];
}
data_left -= len;
if (data_left < 0)
return error;
exp = rqst_exp_find(rqstp ? &rqstp->rq_chandle : NULL,
net, client, gssclient,
fh->fh_fsid_type, fh->fh_fsid);
fid = (struct fid *)(fh->fh_fsid + len);
error = nfserr_stale;
if (IS_ERR(exp)) {
trace_nfsd_set_fh_dentry_badexport(rqstp, fhp, PTR_ERR(exp));
if (PTR_ERR(exp) == -ENOENT)
return error;
return nfserrno(PTR_ERR(exp));
}
if (exp->ex_flags & NFSEXP_NOSUBTREECHECK) {
/* Elevate privileges so that the lack of 'r' or 'x'
* permission on some parent directory will
* not stop exportfs_decode_fh from being able
* to reconnect a directory into the dentry cache.
* The same problem can affect "SUBTREECHECK" exports,
* but as nfsd_acceptable depends on correct
* access control settings being in effect, we cannot
* fix that case easily.
*/
struct cred *new = prepare_creds();
if (!new) {
error = nfserrno(-ENOMEM);
goto out;
}
new->cap_effective =
cap_raise_nfsd_set(new->cap_effective,
new->cap_permitted);
put_cred(override_creds(new));
put_cred(new);
} else {
error = nfsd_setuser_and_check_port(rqstp, cred, exp);
if (error)
goto out;
}
/*
* Look up the dentry using the NFS file handle.
*/
error = nfserr_badhandle;
fileid_type = fh->fh_fileid_type;
if (fileid_type == FILEID_ROOT)
dentry = dget(exp->ex_path.dentry);
else {
dentry = exportfs_decode_fh_raw(exp->ex_path.mnt, fid,
data_left, fileid_type, 0,
nfsd_acceptable, exp);
if (IS_ERR_OR_NULL(dentry)) {
trace_nfsd_set_fh_dentry_badhandle(rqstp, fhp,
dentry ? PTR_ERR(dentry) : -ESTALE);
switch (PTR_ERR(dentry)) {
case -ENOMEM:
case -ETIMEDOUT:
break;
default:
dentry = ERR_PTR(-ESTALE);
}
}
}
if (dentry == NULL)
goto out;
if (IS_ERR(dentry)) {
if (PTR_ERR(dentry) != -EINVAL)
error = nfserrno(PTR_ERR(dentry));
goto out;
}
if (d_is_dir(dentry) &&
(dentry->d_flags & DCACHE_DISCONNECTED)) {
printk("nfsd: find_fh_dentry returned a DISCONNECTED directory: %pd2\n",
dentry);
}
fhp->fh_dentry = dentry;
fhp->fh_export = exp;
switch (fhp->fh_maxsize) {
case NFS4_FHSIZE:
if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR)
fhp->fh_no_atomic_attr = true;
fhp->fh_64bit_cookies = true;
break;
case NFS3_FHSIZE:
if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOWCC)
fhp->fh_no_wcc = true;
fhp->fh_64bit_cookies = true;
if (exp->ex_flags & NFSEXP_V4ROOT)
goto out;
break;
case NFS_FHSIZE:
fhp->fh_no_wcc = true;
if (EX_WGATHER(exp))
fhp->fh_use_wgather = true;
if (exp->ex_flags & NFSEXP_V4ROOT)
goto out;
}
return 0;
out:
exp_put(exp);
return error;
}
/**
* __fh_verify - filehandle lookup and access checking
* @rqstp: RPC transaction context, or NULL
* @net: net namespace in which to perform the export lookup
* @cred: RPC user credential
* @client: RPC auth domain
* @gssclient: RPC GSS auth domain, or NULL
* @fhp: filehandle to be verified
* @type: expected type of object pointed to by filehandle
* @access: type of access needed to object
*
* See fh_verify() for further descriptions of @fhp, @type, and @access.
*/
static __be32
__fh_verify(struct svc_rqst *rqstp,
struct net *net, struct svc_cred *cred,
struct auth_domain *client,
struct auth_domain *gssclient,
struct svc_fh *fhp, umode_t type, int access)
{
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
struct svc_export *exp = NULL;
struct dentry *dentry;
__be32 error;
if (!fhp->fh_dentry) {
error = nfsd_set_fh_dentry(rqstp, net, cred, client,
gssclient, fhp);
if (error)
goto out;
}
dentry = fhp->fh_dentry;
exp = fhp->fh_export;
trace_nfsd_fh_verify(rqstp, fhp, type, access);
/*
* We still have to do all these permission checks, even when
* fh_dentry is already set:
* - fh_verify may be called multiple times with different
* "access" arguments (e.g. nfsd_proc_create calls
* fh_verify(...,NFSD_MAY_EXEC) first, then later (in
* nfsd_create) calls fh_verify(...,NFSD_MAY_CREATE).
* - in the NFSv4 case, the filehandle may have been filled
* in by fh_compose, and given a dentry, but further
* compound operations performed with that filehandle
* still need permissions checks. In the worst case, a
* mountpoint crossing may have changed the export
* options, and we may now need to use a different uid
* (for example, if different id-squashing options are in
* effect on the new filesystem).
*/
error = check_pseudo_root(dentry, exp);
if (error)
goto out;
error = nfsd_setuser_and_check_port(rqstp, cred, exp);
if (error)
goto out;
error = nfsd_mode_check(dentry, type);
if (error)
goto out;
/*
* pseudoflavor restrictions are not enforced on NLM,
* which clients virtually always use auth_sys for,
* even while using RPCSEC_GSS for NFS.
*/
if (access & NFSD_MAY_LOCK || access & NFSD_MAY_BYPASS_GSS)
goto skip_pseudoflavor_check;
/*
* Clients may expect to be able to use auth_sys during mount,
* even if they use gss for everything else; see section 2.3.2
* of rfc 2623.
*/
if (access & NFSD_MAY_BYPASS_GSS_ON_ROOT
&& exp->ex_path.dentry == dentry)
goto skip_pseudoflavor_check;
error = check_nfsd_access(exp, rqstp);
if (error)
goto out;
skip_pseudoflavor_check:
/* Finally, check access permissions. */
error = nfsd_permission(cred, exp, dentry, access);
out:
trace_nfsd_fh_verify_err(rqstp, fhp, type, access, error);
if (error == nfserr_stale)
nfsd_stats_fh_stale_inc(nn, exp);
return error;
}
/**
* fh_verify_local - filehandle lookup and access checking
* @net: net namespace in which to perform the export lookup
* @cred: RPC user credential
* @client: RPC auth domain
* @fhp: filehandle to be verified
* @type: expected type of object pointed to by filehandle
* @access: type of access needed to object
*
* This API can be used by callers who do not have an RPC
* transaction context (ie are not running in an nfsd thread).
*
* See fh_verify() for further descriptions of @fhp, @type, and @access.
*/
__be32
fh_verify_local(struct net *net, struct svc_cred *cred,
struct auth_domain *client, struct svc_fh *fhp,
umode_t type, int access)
{
return __fh_verify(NULL, net, cred, client, NULL,
fhp, type, access);
}
/**
* fh_verify - filehandle lookup and access checking
* @rqstp: pointer to current rpc request
* @fhp: filehandle to be verified
* @type: expected type of object pointed to by filehandle
* @access: type of access needed to object
*
* Look up a dentry from the on-the-wire filehandle, check the client's
* access to the export, and set the current task's credentials.
*
* Regardless of success or failure of fh_verify(), fh_put() should be
* called on @fhp when the caller is finished with the filehandle.
*
* fh_verify() may be called multiple times on a given filehandle, for
* example, when processing an NFSv4 compound. The first call will look
* up a dentry using the on-the-wire filehandle. Subsequent calls will
* skip the lookup and just perform the other checks and possibly change
* the current task's credentials.
*
* @type specifies the type of object expected using one of the S_IF*
* constants defined in include/linux/stat.h. The caller may use zero
* to indicate that it doesn't care, or a negative integer to indicate
* that it expects something not of the given type.
*
* @access is formed from the NFSD_MAY_* constants defined in
* fs/nfsd/vfs.h.
*/
__be32
fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type, int access)
{
return __fh_verify(rqstp, SVC_NET(rqstp), &rqstp->rq_cred,
rqstp->rq_client, rqstp->rq_gssclient,
fhp, type, access);
}
/*
* Compose a file handle for an NFS reply.
*
* Note that when first composed, the dentry may not yet have
* an inode. In this case a call to fh_update should be made
* before the fh goes out on the wire ...
*/
static void _fh_update(struct svc_fh *fhp, struct svc_export *exp,
struct dentry *dentry)
{
if (dentry != exp->ex_path.dentry) {
struct fid *fid = (struct fid *)
(fhp->fh_handle.fh_fsid + fhp->fh_handle.fh_size/4 - 1);
int maxsize = (fhp->fh_maxsize - fhp->fh_handle.fh_size)/4;
int fh_flags = (exp->ex_flags & NFSEXP_NOSUBTREECHECK) ? 0 :
EXPORT_FH_CONNECTABLE;
int fileid_type =
exportfs_encode_fh(dentry, fid, &maxsize, fh_flags);
fhp->fh_handle.fh_fileid_type =
fileid_type > 0 ? fileid_type : FILEID_INVALID;
fhp->fh_handle.fh_size += maxsize * 4;
} else {
fhp->fh_handle.fh_fileid_type = FILEID_ROOT;
}
}
static bool is_root_export(struct svc_export *exp)
{
return exp->ex_path.dentry == exp->ex_path.dentry->d_sb->s_root;
}
static struct super_block *exp_sb(struct svc_export *exp)
{
return exp->ex_path.dentry->d_sb;
}
static bool fsid_type_ok_for_exp(u8 fsid_type, struct svc_export *exp)
{
switch (fsid_type) {
case FSID_DEV:
if (!old_valid_dev(exp_sb(exp)->s_dev))
return false;
fallthrough;
case FSID_MAJOR_MINOR:
case FSID_ENCODE_DEV:
return exp_sb(exp)->s_type->fs_flags & FS_REQUIRES_DEV;
case FSID_NUM:
return exp->ex_flags & NFSEXP_FSID;
case FSID_UUID8:
case FSID_UUID16:
if (!is_root_export(exp))
return false;
fallthrough;
case FSID_UUID4_INUM:
case FSID_UUID16_INUM:
return exp->ex_uuid != NULL;
}
return true;
}
static void set_version_and_fsid_type(struct svc_fh *fhp, struct svc_export *exp, struct svc_fh *ref_fh)
{
u8 version;
u8 fsid_type;
retry:
version = 1;
if (ref_fh && ref_fh->fh_export == exp) {
version = ref_fh->fh_handle.fh_version;
fsid_type = ref_fh->fh_handle.fh_fsid_type;
ref_fh = NULL;
switch (version) {
case 0xca:
fsid_type = FSID_DEV;
break;
case 1:
break;
default:
goto retry;
}
/*
* As the fsid -> filesystem mapping was guided by
* user-space, there is no guarantee that the filesystem
* actually supports that fsid type. If it doesn't we
* loop around again without ref_fh set.
*/
if (!fsid_type_ok_for_exp(fsid_type, exp))
goto retry;
} else if (exp->ex_flags & NFSEXP_FSID) {
fsid_type = FSID_NUM;
} else if (exp->ex_uuid) {
if (fhp->fh_maxsize >= 64) {
if (is_root_export(exp))
fsid_type = FSID_UUID16;
else
fsid_type = FSID_UUID16_INUM;
} else {
if (is_root_export(exp))
fsid_type = FSID_UUID8;
else
fsid_type = FSID_UUID4_INUM;
}
} else if (!old_valid_dev(exp_sb(exp)->s_dev))
/* for newer device numbers, we must use a newer fsid format */
fsid_type = FSID_ENCODE_DEV;
else
fsid_type = FSID_DEV;
fhp->fh_handle.fh_version = version;
if (version)
fhp->fh_handle.fh_fsid_type = fsid_type;
}
__be32
fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
struct svc_fh *ref_fh)
{
/* ref_fh is a reference file handle.
* if it is non-null and for the same filesystem, then we should compose
* a filehandle which is of the same version, where possible.
*/
struct inode * inode = d_inode(dentry);
dev_t ex_dev = exp_sb(exp)->s_dev;
dprintk("nfsd: fh_compose(exp %02x:%02x/%ld %pd2, ino=%ld)\n",
MAJOR(ex_dev), MINOR(ex_dev),
(long) d_inode(exp->ex_path.dentry)->i_ino,
dentry,
(inode ? inode->i_ino : 0));
/* Choose filehandle version and fsid type based on
* the reference filehandle (if it is in the same export)
* or the export options.
*/
set_version_and_fsid_type(fhp, exp, ref_fh);
/* If we have a ref_fh, then copy the fh_no_wcc setting from it. */
fhp->fh_no_wcc = ref_fh ? ref_fh->fh_no_wcc : false;
if (ref_fh == fhp)
fh_put(ref_fh);
if (fhp->fh_dentry) {
printk(KERN_ERR "fh_compose: fh %pd2 not initialized!\n",
dentry);
}
if (fhp->fh_maxsize < NFS_FHSIZE)
printk(KERN_ERR "fh_compose: called with maxsize %d! %pd2\n",
fhp->fh_maxsize,
dentry);
fhp->fh_dentry = dget(dentry); /* our internal copy */
fhp->fh_export = exp_get(exp);
fhp->fh_handle.fh_size =
key_len(fhp->fh_handle.fh_fsid_type) + 4;
fhp->fh_handle.fh_auth_type = 0;
mk_fsid(fhp->fh_handle.fh_fsid_type,
fhp->fh_handle.fh_fsid,
ex_dev,
d_inode(exp->ex_path.dentry)->i_ino,
exp->ex_fsid, exp->ex_uuid);
if (inode)
_fh_update(fhp, exp, dentry);
if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID) {
fh_put(fhp);
return nfserr_stale;
}
return 0;
}
/*
* Update file handle information after changing a dentry.
* This is only called by nfsd_create, nfsd_create_v3 and nfsd_proc_create
*/
__be32
fh_update(struct svc_fh *fhp)
{
struct dentry *dentry;
if (!fhp->fh_dentry)
goto out_bad;
dentry = fhp->fh_dentry;
if (d_really_is_negative(dentry))
goto out_negative;
if (fhp->fh_handle.fh_fileid_type != FILEID_ROOT)
return 0;
_fh_update(fhp, fhp->fh_export, dentry);
if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID)
return nfserr_stale;
return 0;
out_bad:
printk(KERN_ERR "fh_update: fh not verified!\n");
return nfserr_serverfault;
out_negative:
printk(KERN_ERR "fh_update: %pd2 still negative!\n",
dentry);
return nfserr_serverfault;
}
/**
* fh_fill_pre_attrs - Fill in pre-op attributes
* @fhp: file handle to be updated
*
*/
__be32 __must_check fh_fill_pre_attrs(struct svc_fh *fhp)
{
bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
struct inode *inode;
struct kstat stat;
__be32 err;
if (fhp->fh_no_wcc || fhp->fh_pre_saved)
return nfs_ok;
inode = d_inode(fhp->fh_dentry);
err = fh_getattr(fhp, &stat);
if (err)
return err;
if (v4)
fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
fhp->fh_pre_mtime = stat.mtime;
fhp->fh_pre_ctime = stat.ctime;
fhp->fh_pre_size = stat.size;
fhp->fh_pre_saved = true;
return nfs_ok;
}
/**
* fh_fill_post_attrs - Fill in post-op attributes
* @fhp: file handle to be updated
*
*/
__be32 fh_fill_post_attrs(struct svc_fh *fhp)
{
bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
struct inode *inode = d_inode(fhp->fh_dentry);
__be32 err;
if (fhp->fh_no_wcc)
return nfs_ok;
if (fhp->fh_post_saved)
printk("nfsd: inode locked twice during operation.\n");
err = fh_getattr(fhp, &fhp->fh_post_attr);
if (err)
return err;
fhp->fh_post_saved = true;
if (v4)
fhp->fh_post_change =
nfsd4_change_attribute(&fhp->fh_post_attr, inode);
return nfs_ok;
}
/**
* fh_fill_both_attrs - Fill pre-op and post-op attributes
* @fhp: file handle to be updated
*
* This is used when the directory wasn't changed, but wcc attributes
* are needed anyway.
*/
__be32 __must_check fh_fill_both_attrs(struct svc_fh *fhp)
{
__be32 err;
err = fh_fill_post_attrs(fhp);
if (err)
return err;
fhp->fh_pre_change = fhp->fh_post_change;
fhp->fh_pre_mtime = fhp->fh_post_attr.mtime;
fhp->fh_pre_ctime = fhp->fh_post_attr.ctime;
fhp->fh_pre_size = fhp->fh_post_attr.size;
fhp->fh_pre_saved = true;
return nfs_ok;
}
/*
* Release a file handle.
*/
void
fh_put(struct svc_fh *fhp)
{
struct dentry * dentry = fhp->fh_dentry;
struct svc_export * exp = fhp->fh_export;
if (dentry) {
fhp->fh_dentry = NULL;
dput(dentry);
fh_clear_pre_post_attrs(fhp);
}
fh_drop_write(fhp);
if (exp) {
exp_put(exp);
fhp->fh_export = NULL;
}
fhp->fh_no_wcc = false;
return;
}
/*
* Shorthand for dprintk()'s
*/
char * SVCFH_fmt(struct svc_fh *fhp)
{
struct knfsd_fh *fh = &fhp->fh_handle;
static char buf[2+1+1+64*3+1];
if (fh->fh_size < 0 || fh->fh_size> 64)
return "bad-fh";
sprintf(buf, "%d: %*ph", fh->fh_size, fh->fh_size, fh->fh_raw);
return buf;
}
enum fsid_source fsid_source(const struct svc_fh *fhp)
{
if (fhp->fh_handle.fh_version != 1)
return FSIDSOURCE_DEV;
switch(fhp->fh_handle.fh_fsid_type) {
case FSID_DEV:
case FSID_ENCODE_DEV:
case FSID_MAJOR_MINOR:
if (exp_sb(fhp->fh_export)->s_type->fs_flags & FS_REQUIRES_DEV)
return FSIDSOURCE_DEV;
break;
case FSID_NUM:
if (fhp->fh_export->ex_flags & NFSEXP_FSID)
return FSIDSOURCE_FSID;
break;
default:
break;
}
/* either a UUID type filehandle, or the filehandle doesn't
* match the export.
*/
if (fhp->fh_export->ex_flags & NFSEXP_FSID)
return FSIDSOURCE_FSID;
if (fhp->fh_export->ex_uuid)
return FSIDSOURCE_UUID;
return FSIDSOURCE_DEV;
}
/*
* We could use i_version alone as the change attribute. However, i_version
* can go backwards on a regular file after an unclean shutdown. On its own
* that doesn't necessarily cause a problem, but if i_version goes backwards
* and then is incremented again it could reuse a value that was previously
* used before boot, and a client who queried the two values might incorrectly
* assume nothing changed.
*
* By using both ctime and the i_version counter we guarantee that as long as
* time doesn't go backwards we never reuse an old value. If the filesystem
* advertises STATX_ATTR_CHANGE_MONOTONIC, then this mitigation is not
* needed.
*
* We only need to do this for regular files as well. For directories, we
* assume that the new change attr is always logged to stable storage in some
* fashion before the results can be seen.
*/
u64 nfsd4_change_attribute(const struct kstat *stat, const struct inode *inode)
{
u64 chattr;
if (stat->result_mask & STATX_CHANGE_COOKIE) {
chattr = stat->change_cookie;
if (S_ISREG(inode->i_mode) &&
!(stat->attributes & STATX_ATTR_CHANGE_MONOTONIC)) {
chattr += (u64)stat->ctime.tv_sec << 30;
chattr += stat->ctime.tv_nsec;
}
} else {
chattr = time_to_chattr(&stat->ctime);
}
return chattr;
}
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