1 /* 2 * linux/fs/attr.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 * changes by Thomas Schoebel-Theuer 6 */ 7 8 #include <linux/export.h> 9 #include <linux/time.h> 10 #include <linux/mm.h> 11 #include <linux/string.h> 12 #include <linux/capability.h> 13 #include <linux/fsnotify.h> 14 #include <linux/fcntl.h> 15 #include <linux/security.h> 16 #include <linux/evm.h> 17 #include <linux/ima.h> 18 19 /** 20 * setattr_prepare - check if attribute changes to a dentry are allowed 21 * @dentry: dentry to check 22 * @attr: attributes to change 23 * 24 * Check if we are allowed to change the attributes contained in @attr 25 * in the given dentry. This includes the normal unix access permission 26 * checks, as well as checks for rlimits and others. The function also clears 27 * SGID bit from mode if user is not allowed to set it. Also file capabilities 28 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set. 29 * 30 * Should be called as the first thing in ->setattr implementations, 31 * possibly after taking additional locks. 32 */ 33 int setattr_prepare(struct dentry *dentry, struct iattr *attr) 34 { 35 struct inode *inode = d_inode(dentry); 36 unsigned int ia_valid = attr->ia_valid; 37 38 /* 39 * First check size constraints. These can't be overriden using 40 * ATTR_FORCE. 41 */ 42 if (ia_valid & ATTR_SIZE) { 43 int error = inode_newsize_ok(inode, attr->ia_size); 44 if (error) 45 return error; 46 } 47 48 /* If force is set do it anyway. */ 49 if (ia_valid & ATTR_FORCE) 50 goto kill_priv; 51 52 /* Make sure a caller can chown. */ 53 if ((ia_valid & ATTR_UID) && 54 (!uid_eq(current_fsuid(), inode->i_uid) || 55 !uid_eq(attr->ia_uid, inode->i_uid)) && 56 !capable_wrt_inode_uidgid(inode, CAP_CHOWN)) 57 return -EPERM; 58 59 /* Make sure caller can chgrp. */ 60 if ((ia_valid & ATTR_GID) && 61 (!uid_eq(current_fsuid(), inode->i_uid) || 62 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) && 63 !capable_wrt_inode_uidgid(inode, CAP_CHOWN)) 64 return -EPERM; 65 66 /* Make sure a caller can chmod. */ 67 if (ia_valid & ATTR_MODE) { 68 if (!inode_owner_or_capable(inode)) 69 return -EPERM; 70 /* Also check the setgid bit! */ 71 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : 72 inode->i_gid) && 73 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) 74 attr->ia_mode &= ~S_ISGID; 75 } 76 77 /* Check for setting the inode time. */ 78 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { 79 if (!inode_owner_or_capable(inode)) 80 return -EPERM; 81 } 82 83 kill_priv: 84 /* User has permission for the change */ 85 if (ia_valid & ATTR_KILL_PRIV) { 86 int error; 87 88 error = security_inode_killpriv(dentry); 89 if (error) 90 return error; 91 } 92 93 return 0; 94 } 95 EXPORT_SYMBOL(setattr_prepare); 96 97 /** 98 * inode_newsize_ok - may this inode be truncated to a given size 99 * @inode: the inode to be truncated 100 * @offset: the new size to assign to the inode 101 * @Returns: 0 on success, -ve errno on failure 102 * 103 * inode_newsize_ok must be called with i_mutex held. 104 * 105 * inode_newsize_ok will check filesystem limits and ulimits to check that the 106 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ 107 * when necessary. Caller must not proceed with inode size change if failure is 108 * returned. @inode must be a file (not directory), with appropriate 109 * permissions to allow truncate (inode_newsize_ok does NOT check these 110 * conditions). 111 */ 112 int inode_newsize_ok(const struct inode *inode, loff_t offset) 113 { 114 if (inode->i_size < offset) { 115 unsigned long limit; 116 117 limit = rlimit(RLIMIT_FSIZE); 118 if (limit != RLIM_INFINITY && offset > limit) 119 goto out_sig; 120 if (offset > inode->i_sb->s_maxbytes) 121 goto out_big; 122 } else { 123 /* 124 * truncation of in-use swapfiles is disallowed - it would 125 * cause subsequent swapout to scribble on the now-freed 126 * blocks. 127 */ 128 if (IS_SWAPFILE(inode)) 129 return -ETXTBSY; 130 } 131 132 return 0; 133 out_sig: 134 send_sig(SIGXFSZ, current, 0); 135 out_big: 136 return -EFBIG; 137 } 138 EXPORT_SYMBOL(inode_newsize_ok); 139 140 /** 141 * setattr_copy - copy simple metadata updates into the generic inode 142 * @inode: the inode to be updated 143 * @attr: the new attributes 144 * 145 * setattr_copy must be called with i_mutex held. 146 * 147 * setattr_copy updates the inode's metadata with that specified 148 * in attr. Noticeably missing is inode size update, which is more complex 149 * as it requires pagecache updates. 150 * 151 * The inode is not marked as dirty after this operation. The rationale is 152 * that for "simple" filesystems, the struct inode is the inode storage. 153 * The caller is free to mark the inode dirty afterwards if needed. 154 */ 155 void setattr_copy(struct inode *inode, const struct iattr *attr) 156 { 157 unsigned int ia_valid = attr->ia_valid; 158 159 if (ia_valid & ATTR_UID) 160 inode->i_uid = attr->ia_uid; 161 if (ia_valid & ATTR_GID) 162 inode->i_gid = attr->ia_gid; 163 if (ia_valid & ATTR_ATIME) 164 inode->i_atime = timespec_trunc(attr->ia_atime, 165 inode->i_sb->s_time_gran); 166 if (ia_valid & ATTR_MTIME) 167 inode->i_mtime = timespec_trunc(attr->ia_mtime, 168 inode->i_sb->s_time_gran); 169 if (ia_valid & ATTR_CTIME) 170 inode->i_ctime = timespec_trunc(attr->ia_ctime, 171 inode->i_sb->s_time_gran); 172 if (ia_valid & ATTR_MODE) { 173 umode_t mode = attr->ia_mode; 174 175 if (!in_group_p(inode->i_gid) && 176 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) 177 mode &= ~S_ISGID; 178 inode->i_mode = mode; 179 } 180 } 181 EXPORT_SYMBOL(setattr_copy); 182 183 /** 184 * notify_change - modify attributes of a filesytem object 185 * @dentry: object affected 186 * @iattr: new attributes 187 * @delegated_inode: returns inode, if the inode is delegated 188 * 189 * The caller must hold the i_mutex on the affected object. 190 * 191 * If notify_change discovers a delegation in need of breaking, 192 * it will return -EWOULDBLOCK and return a reference to the inode in 193 * delegated_inode. The caller should then break the delegation and 194 * retry. Because breaking a delegation may take a long time, the 195 * caller should drop the i_mutex before doing so. 196 * 197 * Alternatively, a caller may pass NULL for delegated_inode. This may 198 * be appropriate for callers that expect the underlying filesystem not 199 * to be NFS exported. Also, passing NULL is fine for callers holding 200 * the file open for write, as there can be no conflicting delegation in 201 * that case. 202 */ 203 int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode) 204 { 205 struct inode *inode = dentry->d_inode; 206 umode_t mode = inode->i_mode; 207 int error; 208 struct timespec now; 209 unsigned int ia_valid = attr->ia_valid; 210 211 WARN_ON_ONCE(!inode_is_locked(inode)); 212 213 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { 214 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 215 return -EPERM; 216 } 217 218 /* 219 * If utimes(2) and friends are called with times == NULL (or both 220 * times are UTIME_NOW), then we need to check for write permission 221 */ 222 if (ia_valid & ATTR_TOUCH) { 223 if (IS_IMMUTABLE(inode)) 224 return -EPERM; 225 226 if (!inode_owner_or_capable(inode)) { 227 error = inode_permission(inode, MAY_WRITE); 228 if (error) 229 return error; 230 } 231 } 232 233 if ((ia_valid & ATTR_MODE)) { 234 umode_t amode = attr->ia_mode; 235 /* Flag setting protected by i_mutex */ 236 if (is_sxid(amode)) 237 inode->i_flags &= ~S_NOSEC; 238 } 239 240 now = current_time(inode); 241 242 attr->ia_ctime = now; 243 if (!(ia_valid & ATTR_ATIME_SET)) 244 attr->ia_atime = now; 245 if (!(ia_valid & ATTR_MTIME_SET)) 246 attr->ia_mtime = now; 247 if (ia_valid & ATTR_KILL_PRIV) { 248 error = security_inode_need_killpriv(dentry); 249 if (error < 0) 250 return error; 251 if (error == 0) 252 ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV; 253 } 254 255 /* 256 * We now pass ATTR_KILL_S*ID to the lower level setattr function so 257 * that the function has the ability to reinterpret a mode change 258 * that's due to these bits. This adds an implicit restriction that 259 * no function will ever call notify_change with both ATTR_MODE and 260 * ATTR_KILL_S*ID set. 261 */ 262 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && 263 (ia_valid & ATTR_MODE)) 264 BUG(); 265 266 if (ia_valid & ATTR_KILL_SUID) { 267 if (mode & S_ISUID) { 268 ia_valid = attr->ia_valid |= ATTR_MODE; 269 attr->ia_mode = (inode->i_mode & ~S_ISUID); 270 } 271 } 272 if (ia_valid & ATTR_KILL_SGID) { 273 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 274 if (!(ia_valid & ATTR_MODE)) { 275 ia_valid = attr->ia_valid |= ATTR_MODE; 276 attr->ia_mode = inode->i_mode; 277 } 278 attr->ia_mode &= ~S_ISGID; 279 } 280 } 281 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) 282 return 0; 283 284 /* 285 * Verify that uid/gid changes are valid in the target 286 * namespace of the superblock. 287 */ 288 if (ia_valid & ATTR_UID && 289 !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid)) 290 return -EOVERFLOW; 291 if (ia_valid & ATTR_GID && 292 !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid)) 293 return -EOVERFLOW; 294 295 /* Don't allow modifications of files with invalid uids or 296 * gids unless those uids & gids are being made valid. 297 */ 298 if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid)) 299 return -EOVERFLOW; 300 if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid)) 301 return -EOVERFLOW; 302 303 error = security_inode_setattr(dentry, attr); 304 if (error) 305 return error; 306 error = try_break_deleg(inode, delegated_inode); 307 if (error) 308 return error; 309 310 if (inode->i_op->setattr) 311 error = inode->i_op->setattr(dentry, attr); 312 else 313 error = simple_setattr(dentry, attr); 314 315 if (!error) { 316 fsnotify_change(dentry, ia_valid); 317 ima_inode_post_setattr(dentry); 318 evm_inode_post_setattr(dentry, ia_valid); 319 } 320 321 return error; 322 } 323 EXPORT_SYMBOL(notify_change); 324