linux/fs/nfsd/nfsfh.c

// 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 …


/*
 * 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)
{ … }

/* 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 svc_rqst *rqstp, struct dentry *dentry,
		umode_t requested)
{ … }

static bool nfsd_originating_port_ok(struct svc_rqst *rqstp, int flags)
{ … }

static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
					  struct svc_export *exp)
{ … }

static inline __be32 check_pseudo_root(struct svc_rqst *rqstp,
	struct dentry *dentry, struct svc_export *exp)
{ … }

/*
 * 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 svc_fh *fhp)
{ … }

/**
 * 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)
{ … }


/*
 * 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)
{ … }

static bool is_root_export(struct svc_export *exp)
{ … }

static struct super_block *exp_sb(struct svc_export *exp)
{ … }

static bool fsid_type_ok_for_exp(u8 fsid_type, struct svc_export *exp)
{ … }


static void set_version_and_fsid_type(struct svc_fh *fhp, struct svc_export *exp, struct svc_fh *ref_fh)
{ … }

__be32
fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
	   struct svc_fh *ref_fh)
{ … }

/*
 * 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)
{ … }

/**
 * 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)
{ … }

/**
 * fh_fill_post_attrs - Fill in post-op attributes
 * @fhp: file handle to be updated
 *
 */
__be32 fh_fill_post_attrs(struct svc_fh *fhp)
{ … }

/**
 * 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)
{ … }

/*
 * Release a file handle.
 */
void
fh_put(struct svc_fh *fhp)
{ … }

/*
 * Shorthand for dprintk()'s
 */
char * SVCFH_fmt(struct svc_fh *fhp)
{ … }

enum fsid_source fsid_source(const struct svc_fh *fhp)
{ … }

/*
 * 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)
{ … }