From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- fs/nfsd/nfsfh.c | 789 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 789 insertions(+) create mode 100644 fs/nfsd/nfsfh.c (limited to 'fs/nfsd/nfsfh.c') diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c new file mode 100644 index 000000000..355bf0db3 --- /dev/null +++ b/fs/nfsd/nfsfh.c @@ -0,0 +1,789 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * NFS server file handle treatment. + * + * Copyright (C) 1995, 1996 Olaf Kirch + * Portions Copyright (C) 1999 G. Allen Morris III + * Extensive rewrite by Neil Brown Southern-Spring 1999 + * ... and again Southern-Winter 2001 to support export_operations + */ + +#include + +#include +#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 svc_rqst *rqstp, 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; + } + /* + * v4 has an error more specific than err_notdir which we should + * return in preference to err_notdir: + */ + if (rqstp->rq_vers == 4 && mode == S_IFLNK) + return nfserr_symlink; + if (requested == S_IFDIR) + return nfserr_notdir; + if (mode == S_IFDIR) + return nfserr_isdir; + return nfserr_inval; +} + +static bool nfsd_originating_port_ok(struct svc_rqst *rqstp, int flags) +{ + if (flags & NFSEXP_INSECURE_PORT) + return true; + /* We don't require gss requests to use low ports: */ + if (rqstp->rq_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_export *exp) +{ + int flags = nfsexp_flags(rqstp, exp); + + /* Check if the request originated from a secure port. */ + if (!nfsd_originating_port_ok(rqstp, flags)) { + 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(rqstp, exp)); +} + +static inline __be32 check_pseudo_root(struct svc_rqst *rqstp, + struct dentry *dentry, struct svc_export *exp) +{ + if (!(exp->ex_flags & NFSEXP_V4ROOT)) + return nfs_ok; + /* + * v2/v3 clients have no need for the V4ROOT export--they use + * the mount protocl instead; also, further V4ROOT checks may be + * in v4-specific code, in which case v2/v3 clients could bypass + * them. + */ + if (!nfsd_v4client(rqstp)) + return nfserr_stale; + /* + * 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 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_stale; + if (rqstp->rq_vers > 2) + error = nfserr_badhandle; + if (rqstp->rq_vers == 4 && 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, 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, exp); + if (error) + goto out; + } + + /* + * Look up the dentry using the NFS file handle. + */ + error = nfserr_stale; + if (rqstp->rq_vers > 2) + 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, + 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 (rqstp->rq_vers) { + case 4: + if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR) + fhp->fh_no_atomic_attr = true; + break; + case 3: + if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOWCC) + fhp->fh_no_wcc = true; + break; + case 2: + fhp->fh_no_wcc = true; + } + + return 0; +out: + exp_put(exp); + return error; +} + +/** + * 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) +{ + struct svc_export *exp = NULL; + struct dentry *dentry; + __be32 error; + + if (!fhp->fh_dentry) { + error = nfsd_set_fh_dentry(rqstp, 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(rqstp, dentry, exp); + if (error) + goto out; + + error = nfsd_setuser_and_check_port(rqstp, exp); + if (error) + goto out; + + error = nfsd_mode_check(rqstp, 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(rqstp, exp, dentry, access); +out: + trace_nfsd_fh_verify_err(rqstp, fhp, type, access, error); + if (error == nfserr_stale) + nfsd_stats_fh_stale_inc(exp); + return error; +} + + +/* + * 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_opnotsupp; + } + + 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_opnotsupp; + 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(struct kstat *stat, 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; +} -- cgit v1.2.3