Amir Goldstein | 8ed5eec | 2017-07-12 14:17:16 +0300 | [diff] [blame] | 1 | /* |
| 2 | * Overlayfs NFS export support. |
| 3 | * |
| 4 | * Amir Goldstein <amir73il@gmail.com> |
| 5 | * |
| 6 | * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved. |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify it |
| 9 | * under the terms of the GNU General Public License version 2 as published by |
| 10 | * the Free Software Foundation. |
| 11 | */ |
| 12 | |
| 13 | #include <linux/fs.h> |
| 14 | #include <linux/cred.h> |
| 15 | #include <linux/mount.h> |
| 16 | #include <linux/namei.h> |
| 17 | #include <linux/xattr.h> |
| 18 | #include <linux/exportfs.h> |
| 19 | #include <linux/ratelimit.h> |
| 20 | #include "overlayfs.h" |
| 21 | |
| 22 | static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) |
| 23 | { |
| 24 | struct dentry *upper = ovl_dentry_upper(dentry); |
| 25 | struct dentry *origin = ovl_dentry_lower(dentry); |
| 26 | struct ovl_fh *fh = NULL; |
| 27 | int err; |
| 28 | |
| 29 | /* |
| 30 | * On overlay with an upper layer, overlay root inode is encoded as |
| 31 | * an upper file handle, because upper root dir is not indexed. |
| 32 | */ |
| 33 | if (dentry == dentry->d_sb->s_root && upper) |
| 34 | origin = NULL; |
| 35 | |
| 36 | err = -EACCES; |
| 37 | if (!upper || origin) |
| 38 | goto fail; |
| 39 | |
| 40 | /* TODO: encode non pure-upper by origin */ |
| 41 | fh = ovl_encode_fh(upper, true); |
| 42 | |
| 43 | err = -EOVERFLOW; |
| 44 | if (fh->len > buflen) |
| 45 | goto fail; |
| 46 | |
| 47 | memcpy(buf, (char *)fh, fh->len); |
| 48 | err = fh->len; |
| 49 | |
| 50 | out: |
| 51 | kfree(fh); |
| 52 | return err; |
| 53 | |
| 54 | fail: |
| 55 | pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n", |
| 56 | dentry, err, buflen, fh ? (int)fh->len : 0, |
| 57 | fh ? fh->type : 0); |
| 58 | goto out; |
| 59 | } |
| 60 | |
| 61 | static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len) |
| 62 | { |
| 63 | int res, len = *max_len << 2; |
| 64 | |
| 65 | res = ovl_d_to_fh(dentry, (char *)fid, len); |
| 66 | if (res <= 0) |
| 67 | return FILEID_INVALID; |
| 68 | |
| 69 | len = res; |
| 70 | |
| 71 | /* Round up to dwords */ |
| 72 | *max_len = (len + 3) >> 2; |
| 73 | return OVL_FILEID; |
| 74 | } |
| 75 | |
| 76 | static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len, |
| 77 | struct inode *parent) |
| 78 | { |
| 79 | struct dentry *dentry; |
| 80 | int type; |
| 81 | |
| 82 | /* TODO: encode connectable file handles */ |
| 83 | if (parent) |
| 84 | return FILEID_INVALID; |
| 85 | |
| 86 | dentry = d_find_any_alias(inode); |
| 87 | if (WARN_ON(!dentry)) |
| 88 | return FILEID_INVALID; |
| 89 | |
| 90 | type = ovl_dentry_to_fh(dentry, fid, max_len); |
| 91 | |
| 92 | dput(dentry); |
| 93 | return type; |
| 94 | } |
| 95 | |
Amir Goldstein | 8556a42 | 2018-01-19 01:03:23 +0200 | [diff] [blame^] | 96 | /* |
| 97 | * Find or instantiate an overlay dentry from real dentries. |
| 98 | */ |
| 99 | static struct dentry *ovl_obtain_alias(struct super_block *sb, |
| 100 | struct dentry *upper, |
| 101 | struct ovl_path *lowerpath) |
| 102 | { |
| 103 | struct inode *inode; |
| 104 | struct dentry *dentry; |
| 105 | struct ovl_entry *oe; |
| 106 | void *fsdata = &oe; |
| 107 | |
| 108 | /* TODO: obtain non pure-upper */ |
| 109 | if (lowerpath) |
| 110 | return ERR_PTR(-EIO); |
| 111 | |
| 112 | inode = ovl_get_inode(sb, dget(upper), NULL, NULL, 0); |
| 113 | if (IS_ERR(inode)) { |
| 114 | dput(upper); |
| 115 | return ERR_CAST(inode); |
| 116 | } |
| 117 | |
| 118 | dentry = d_find_any_alias(inode); |
| 119 | if (!dentry) { |
| 120 | dentry = d_alloc_anon(inode->i_sb); |
| 121 | if (!dentry) |
| 122 | goto nomem; |
| 123 | oe = ovl_alloc_entry(0); |
| 124 | if (!oe) |
| 125 | goto nomem; |
| 126 | |
| 127 | dentry->d_fsdata = oe; |
| 128 | ovl_dentry_set_upper_alias(dentry); |
| 129 | } |
| 130 | |
| 131 | return d_instantiate_anon(dentry, inode); |
| 132 | |
| 133 | nomem: |
| 134 | iput(inode); |
| 135 | dput(dentry); |
| 136 | return ERR_PTR(-ENOMEM); |
| 137 | } |
| 138 | |
| 139 | static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, |
| 140 | struct ovl_fh *fh) |
| 141 | { |
| 142 | struct ovl_fs *ofs = sb->s_fs_info; |
| 143 | struct dentry *dentry; |
| 144 | struct dentry *upper; |
| 145 | |
| 146 | if (!ofs->upper_mnt) |
| 147 | return ERR_PTR(-EACCES); |
| 148 | |
| 149 | upper = ovl_decode_fh(fh, ofs->upper_mnt); |
| 150 | if (IS_ERR_OR_NULL(upper)) |
| 151 | return upper; |
| 152 | |
| 153 | dentry = ovl_obtain_alias(sb, upper, NULL); |
| 154 | dput(upper); |
| 155 | |
| 156 | return dentry; |
| 157 | } |
| 158 | |
| 159 | static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, |
| 160 | int fh_len, int fh_type) |
| 161 | { |
| 162 | struct dentry *dentry = NULL; |
| 163 | struct ovl_fh *fh = (struct ovl_fh *) fid; |
| 164 | int len = fh_len << 2; |
| 165 | unsigned int flags = 0; |
| 166 | int err; |
| 167 | |
| 168 | err = -EINVAL; |
| 169 | if (fh_type != OVL_FILEID) |
| 170 | goto out_err; |
| 171 | |
| 172 | err = ovl_check_fh_len(fh, len); |
| 173 | if (err) |
| 174 | goto out_err; |
| 175 | |
| 176 | /* TODO: decode non-upper */ |
| 177 | flags = fh->flags; |
| 178 | if (flags & OVL_FH_FLAG_PATH_UPPER) |
| 179 | dentry = ovl_upper_fh_to_d(sb, fh); |
| 180 | err = PTR_ERR(dentry); |
| 181 | if (IS_ERR(dentry) && err != -ESTALE) |
| 182 | goto out_err; |
| 183 | |
| 184 | return dentry; |
| 185 | |
| 186 | out_err: |
| 187 | pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", |
| 188 | len, fh_type, flags, err); |
| 189 | return ERR_PTR(err); |
| 190 | } |
| 191 | |
Amir Goldstein | 8ed5eec | 2017-07-12 14:17:16 +0300 | [diff] [blame] | 192 | const struct export_operations ovl_export_operations = { |
| 193 | .encode_fh = ovl_encode_inode_fh, |
Amir Goldstein | 8556a42 | 2018-01-19 01:03:23 +0200 | [diff] [blame^] | 194 | .fh_to_dentry = ovl_fh_to_dentry, |
Amir Goldstein | 8ed5eec | 2017-07-12 14:17:16 +0300 | [diff] [blame] | 195 | }; |