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 18 /** 19 * inode_change_ok - check if attribute changes to an inode are allowed 20 * @inode: inode to check 21 * @attr: attributes to change 22 * 23 * Check if we are allowed to change the attributes contained in @attr 24 * in the given inode. This includes the normal unix access permission 25 * checks, as well as checks for rlimits and others. 26 * 27 * Should be called as the first thing in ->setattr implementations, 28 * possibly after taking additional locks. 29 */ 30 int inode_change_ok(const struct inode *inode, struct iattr *attr) 31 { 32 unsigned int ia_valid = attr->ia_valid; 33 34 /* 35 * First check size constraints. These can't be overriden using 36 * ATTR_FORCE. 37 */ 38 if (ia_valid & ATTR_SIZE) { 39 int error = inode_newsize_ok(inode, attr->ia_size); 40 if (error) 41 return error; 42 } 43 44 /* If force is set do it anyway. */ 45 if (ia_valid & ATTR_FORCE) 46 return 0; 47 48 /* Make sure a caller can chown. */ 49 if ((ia_valid & ATTR_UID) && 50 (!uid_eq(current_fsuid(), inode->i_uid) || 51 !uid_eq(attr->ia_uid, inode->i_uid)) && !capable(CAP_CHOWN)) 52 return -EPERM; 53 54 /* Make sure caller can chgrp. */ 55 if ((ia_valid & ATTR_GID) && 56 (!uid_eq(current_fsuid(), inode->i_uid) || 57 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) && 58 !capable(CAP_CHOWN)) 59 return -EPERM; 60 61 /* Make sure a caller can chmod. */ 62 if (ia_valid & ATTR_MODE) { 63 if (!inode_owner_or_capable(inode)) 64 return -EPERM; 65 /* Also check the setgid bit! */ 66 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : 67 inode->i_gid) && !capable(CAP_FSETID)) 68 attr->ia_mode &= ~S_ISGID; 69 } 70 71 /* Check for setting the inode time. */ 72 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { 73 if (!inode_owner_or_capable(inode)) 74 return -EPERM; 75 } 76 77 return 0; 78 } 79 EXPORT_SYMBOL(inode_change_ok); 80 81 /** 82 * inode_newsize_ok - may this inode be truncated to a given size 83 * @inode: the inode to be truncated 84 * @offset: the new size to assign to the inode 85 * @Returns: 0 on success, -ve errno on failure 86 * 87 * inode_newsize_ok must be called with i_mutex held. 88 * 89 * inode_newsize_ok will check filesystem limits and ulimits to check that the 90 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ 91 * when necessary. Caller must not proceed with inode size change if failure is 92 * returned. @inode must be a file (not directory), with appropriate 93 * permissions to allow truncate (inode_newsize_ok does NOT check these 94 * conditions). 95 */ 96 int inode_newsize_ok(const struct inode *inode, loff_t offset) 97 { 98 if (inode->i_size < offset) { 99 unsigned long limit; 100 101 limit = rlimit(RLIMIT_FSIZE); 102 if (limit != RLIM_INFINITY && offset > limit) 103 goto out_sig; 104 if (offset > inode->i_sb->s_maxbytes) 105 goto out_big; 106 } else { 107 /* 108 * truncation of in-use swapfiles is disallowed - it would 109 * cause subsequent swapout to scribble on the now-freed 110 * blocks. 111 */ 112 if (IS_SWAPFILE(inode)) 113 return -ETXTBSY; 114 } 115 116 return 0; 117 out_sig: 118 send_sig(SIGXFSZ, current, 0); 119 out_big: 120 return -EFBIG; 121 } 122 EXPORT_SYMBOL(inode_newsize_ok); 123 124 /** 125 * setattr_copy - copy simple metadata updates into the generic inode 126 * @inode: the inode to be updated 127 * @attr: the new attributes 128 * 129 * setattr_copy must be called with i_mutex held. 130 * 131 * setattr_copy updates the inode's metadata with that specified 132 * in attr. Noticeably missing is inode size update, which is more complex 133 * as it requires pagecache updates. 134 * 135 * The inode is not marked as dirty after this operation. The rationale is 136 * that for "simple" filesystems, the struct inode is the inode storage. 137 * The caller is free to mark the inode dirty afterwards if needed. 138 */ 139 void setattr_copy(struct inode *inode, const struct iattr *attr) 140 { 141 unsigned int ia_valid = attr->ia_valid; 142 143 if (ia_valid & ATTR_UID) 144 inode->i_uid = attr->ia_uid; 145 if (ia_valid & ATTR_GID) 146 inode->i_gid = attr->ia_gid; 147 if (ia_valid & ATTR_ATIME) 148 inode->i_atime = timespec_trunc(attr->ia_atime, 149 inode->i_sb->s_time_gran); 150 if (ia_valid & ATTR_MTIME) 151 inode->i_mtime = timespec_trunc(attr->ia_mtime, 152 inode->i_sb->s_time_gran); 153 if (ia_valid & ATTR_CTIME) 154 inode->i_ctime = timespec_trunc(attr->ia_ctime, 155 inode->i_sb->s_time_gran); 156 if (ia_valid & ATTR_MODE) { 157 umode_t mode = attr->ia_mode; 158 159 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID)) 160 mode &= ~S_ISGID; 161 inode->i_mode = mode; 162 } 163 } 164 EXPORT_SYMBOL(setattr_copy); 165 166 int notify_change(struct dentry * dentry, struct iattr * attr) 167 { 168 struct inode *inode = dentry->d_inode; 169 umode_t mode = inode->i_mode; 170 int error; 171 struct timespec now; 172 unsigned int ia_valid = attr->ia_valid; 173 174 WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex)); 175 176 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { 177 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 178 return -EPERM; 179 } 180 181 if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) { 182 if (attr->ia_size != inode->i_size) 183 inode_inc_iversion(inode); 184 } 185 186 if ((ia_valid & ATTR_MODE)) { 187 umode_t amode = attr->ia_mode; 188 /* Flag setting protected by i_mutex */ 189 if (is_sxid(amode)) 190 inode->i_flags &= ~S_NOSEC; 191 } 192 193 now = current_fs_time(inode->i_sb); 194 195 attr->ia_ctime = now; 196 if (!(ia_valid & ATTR_ATIME_SET)) 197 attr->ia_atime = now; 198 if (!(ia_valid & ATTR_MTIME_SET)) 199 attr->ia_mtime = now; 200 if (ia_valid & ATTR_KILL_PRIV) { 201 attr->ia_valid &= ~ATTR_KILL_PRIV; 202 ia_valid &= ~ATTR_KILL_PRIV; 203 error = security_inode_need_killpriv(dentry); 204 if (error > 0) 205 error = security_inode_killpriv(dentry); 206 if (error) 207 return error; 208 } 209 210 /* 211 * We now pass ATTR_KILL_S*ID to the lower level setattr function so 212 * that the function has the ability to reinterpret a mode change 213 * that's due to these bits. This adds an implicit restriction that 214 * no function will ever call notify_change with both ATTR_MODE and 215 * ATTR_KILL_S*ID set. 216 */ 217 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && 218 (ia_valid & ATTR_MODE)) 219 BUG(); 220 221 if (ia_valid & ATTR_KILL_SUID) { 222 if (mode & S_ISUID) { 223 ia_valid = attr->ia_valid |= ATTR_MODE; 224 attr->ia_mode = (inode->i_mode & ~S_ISUID); 225 } 226 } 227 if (ia_valid & ATTR_KILL_SGID) { 228 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 229 if (!(ia_valid & ATTR_MODE)) { 230 ia_valid = attr->ia_valid |= ATTR_MODE; 231 attr->ia_mode = inode->i_mode; 232 } 233 attr->ia_mode &= ~S_ISGID; 234 } 235 } 236 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) 237 return 0; 238 239 error = security_inode_setattr(dentry, attr); 240 if (error) 241 return error; 242 243 if (inode->i_op->setattr) 244 error = inode->i_op->setattr(dentry, attr); 245 else 246 error = simple_setattr(dentry, attr); 247 248 if (!error) { 249 fsnotify_change(dentry, ia_valid); 250 evm_inode_post_setattr(dentry, ia_valid); 251 } 252 253 return error; 254 } 255 EXPORT_SYMBOL(notify_change); 256