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)) && !capable(CAP_CHOWN)) 53 return -EPERM; 54 55 /* Make sure caller can chgrp. */ 56 if ((ia_valid & ATTR_GID) && 57 (!uid_eq(current_fsuid(), inode->i_uid) || 58 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) && 59 !capable(CAP_CHOWN)) 60 return -EPERM; 61 62 /* Make sure a caller can chmod. */ 63 if (ia_valid & ATTR_MODE) { 64 if (!inode_owner_or_capable(inode)) 65 return -EPERM; 66 /* Also check the setgid bit! */ 67 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : 68 inode->i_gid) && !capable(CAP_FSETID)) 69 attr->ia_mode &= ~S_ISGID; 70 } 71 72 /* Check for setting the inode time. */ 73 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { 74 if (!inode_owner_or_capable(inode)) 75 return -EPERM; 76 } 77 78 return 0; 79 } 80 EXPORT_SYMBOL(inode_change_ok); 81 82 /** 83 * inode_newsize_ok - may this inode be truncated to a given size 84 * @inode: the inode to be truncated 85 * @offset: the new size to assign to the inode 86 * @Returns: 0 on success, -ve errno on failure 87 * 88 * inode_newsize_ok must be called with i_mutex held. 89 * 90 * inode_newsize_ok will check filesystem limits and ulimits to check that the 91 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ 92 * when necessary. Caller must not proceed with inode size change if failure is 93 * returned. @inode must be a file (not directory), with appropriate 94 * permissions to allow truncate (inode_newsize_ok does NOT check these 95 * conditions). 96 */ 97 int inode_newsize_ok(const struct inode *inode, loff_t offset) 98 { 99 if (inode->i_size < offset) { 100 unsigned long limit; 101 102 limit = rlimit(RLIMIT_FSIZE); 103 if (limit != RLIM_INFINITY && offset > limit) 104 goto out_sig; 105 if (offset > inode->i_sb->s_maxbytes) 106 goto out_big; 107 } else { 108 /* 109 * truncation of in-use swapfiles is disallowed - it would 110 * cause subsequent swapout to scribble on the now-freed 111 * blocks. 112 */ 113 if (IS_SWAPFILE(inode)) 114 return -ETXTBSY; 115 } 116 117 return 0; 118 out_sig: 119 send_sig(SIGXFSZ, current, 0); 120 out_big: 121 return -EFBIG; 122 } 123 EXPORT_SYMBOL(inode_newsize_ok); 124 125 /** 126 * setattr_copy - copy simple metadata updates into the generic inode 127 * @inode: the inode to be updated 128 * @attr: the new attributes 129 * 130 * setattr_copy must be called with i_mutex held. 131 * 132 * setattr_copy updates the inode's metadata with that specified 133 * in attr. Noticeably missing is inode size update, which is more complex 134 * as it requires pagecache updates. 135 * 136 * The inode is not marked as dirty after this operation. The rationale is 137 * that for "simple" filesystems, the struct inode is the inode storage. 138 * The caller is free to mark the inode dirty afterwards if needed. 139 */ 140 void setattr_copy(struct inode *inode, const struct iattr *attr) 141 { 142 unsigned int ia_valid = attr->ia_valid; 143 144 if (ia_valid & ATTR_UID) 145 inode->i_uid = attr->ia_uid; 146 if (ia_valid & ATTR_GID) 147 inode->i_gid = attr->ia_gid; 148 if (ia_valid & ATTR_ATIME) 149 inode->i_atime = timespec_trunc(attr->ia_atime, 150 inode->i_sb->s_time_gran); 151 if (ia_valid & ATTR_MTIME) 152 inode->i_mtime = timespec_trunc(attr->ia_mtime, 153 inode->i_sb->s_time_gran); 154 if (ia_valid & ATTR_CTIME) 155 inode->i_ctime = timespec_trunc(attr->ia_ctime, 156 inode->i_sb->s_time_gran); 157 if (ia_valid & ATTR_MODE) { 158 umode_t mode = attr->ia_mode; 159 160 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID)) 161 mode &= ~S_ISGID; 162 inode->i_mode = mode; 163 } 164 } 165 EXPORT_SYMBOL(setattr_copy); 166 167 int notify_change(struct dentry * dentry, struct iattr * attr) 168 { 169 struct inode *inode = dentry->d_inode; 170 umode_t mode = inode->i_mode; 171 int error; 172 struct timespec now; 173 unsigned int ia_valid = attr->ia_valid; 174 175 WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex)); 176 177 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { 178 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 179 return -EPERM; 180 } 181 182 if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) { 183 if (attr->ia_size != inode->i_size) 184 inode_inc_iversion(inode); 185 } 186 187 if ((ia_valid & ATTR_MODE)) { 188 umode_t amode = attr->ia_mode; 189 /* Flag setting protected by i_mutex */ 190 if (is_sxid(amode)) 191 inode->i_flags &= ~S_NOSEC; 192 } 193 194 now = current_fs_time(inode->i_sb); 195 196 attr->ia_ctime = now; 197 if (!(ia_valid & ATTR_ATIME_SET)) 198 attr->ia_atime = now; 199 if (!(ia_valid & ATTR_MTIME_SET)) 200 attr->ia_mtime = now; 201 if (ia_valid & ATTR_KILL_PRIV) { 202 attr->ia_valid &= ~ATTR_KILL_PRIV; 203 ia_valid &= ~ATTR_KILL_PRIV; 204 error = security_inode_need_killpriv(dentry); 205 if (error > 0) 206 error = security_inode_killpriv(dentry); 207 if (error) 208 return error; 209 } 210 211 /* 212 * We now pass ATTR_KILL_S*ID to the lower level setattr function so 213 * that the function has the ability to reinterpret a mode change 214 * that's due to these bits. This adds an implicit restriction that 215 * no function will ever call notify_change with both ATTR_MODE and 216 * ATTR_KILL_S*ID set. 217 */ 218 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && 219 (ia_valid & ATTR_MODE)) 220 BUG(); 221 222 if (ia_valid & ATTR_KILL_SUID) { 223 if (mode & S_ISUID) { 224 ia_valid = attr->ia_valid |= ATTR_MODE; 225 attr->ia_mode = (inode->i_mode & ~S_ISUID); 226 } 227 } 228 if (ia_valid & ATTR_KILL_SGID) { 229 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 230 if (!(ia_valid & ATTR_MODE)) { 231 ia_valid = attr->ia_valid |= ATTR_MODE; 232 attr->ia_mode = inode->i_mode; 233 } 234 attr->ia_mode &= ~S_ISGID; 235 } 236 } 237 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) 238 return 0; 239 240 error = security_inode_setattr(dentry, attr); 241 if (error) 242 return error; 243 244 if (inode->i_op->setattr) 245 error = inode->i_op->setattr(dentry, attr); 246 else 247 error = simple_setattr(dentry, attr); 248 249 if (!error) { 250 fsnotify_change(dentry, ia_valid); 251 ima_inode_post_setattr(dentry); 252 evm_inode_post_setattr(dentry, ia_valid); 253 } 254 255 return error; 256 } 257 EXPORT_SYMBOL(notify_change); 258