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