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 int notify_change(struct dentry * dentry, struct iattr * attr) 171 { 172 struct inode *inode = dentry->d_inode; 173 umode_t mode = inode->i_mode; 174 int error; 175 struct timespec now; 176 unsigned int ia_valid = attr->ia_valid; 177 178 WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex)); 179 180 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { 181 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 182 return -EPERM; 183 } 184 185 if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) { 186 if (attr->ia_size != inode->i_size) 187 inode_inc_iversion(inode); 188 } 189 190 if ((ia_valid & ATTR_MODE)) { 191 umode_t amode = attr->ia_mode; 192 /* Flag setting protected by i_mutex */ 193 if (is_sxid(amode)) 194 inode->i_flags &= ~S_NOSEC; 195 } 196 197 now = current_fs_time(inode->i_sb); 198 199 attr->ia_ctime = now; 200 if (!(ia_valid & ATTR_ATIME_SET)) 201 attr->ia_atime = now; 202 if (!(ia_valid & ATTR_MTIME_SET)) 203 attr->ia_mtime = now; 204 if (ia_valid & ATTR_KILL_PRIV) { 205 attr->ia_valid &= ~ATTR_KILL_PRIV; 206 ia_valid &= ~ATTR_KILL_PRIV; 207 error = security_inode_need_killpriv(dentry); 208 if (error > 0) 209 error = security_inode_killpriv(dentry); 210 if (error) 211 return error; 212 } 213 214 /* 215 * We now pass ATTR_KILL_S*ID to the lower level setattr function so 216 * that the function has the ability to reinterpret a mode change 217 * that's due to these bits. This adds an implicit restriction that 218 * no function will ever call notify_change with both ATTR_MODE and 219 * ATTR_KILL_S*ID set. 220 */ 221 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && 222 (ia_valid & ATTR_MODE)) 223 BUG(); 224 225 if (ia_valid & ATTR_KILL_SUID) { 226 if (mode & S_ISUID) { 227 ia_valid = attr->ia_valid |= ATTR_MODE; 228 attr->ia_mode = (inode->i_mode & ~S_ISUID); 229 } 230 } 231 if (ia_valid & ATTR_KILL_SGID) { 232 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 233 if (!(ia_valid & ATTR_MODE)) { 234 ia_valid = attr->ia_valid |= ATTR_MODE; 235 attr->ia_mode = inode->i_mode; 236 } 237 attr->ia_mode &= ~S_ISGID; 238 } 239 } 240 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) 241 return 0; 242 243 error = security_inode_setattr(dentry, attr); 244 if (error) 245 return error; 246 247 if (inode->i_op->setattr) 248 error = inode->i_op->setattr(dentry, attr); 249 else 250 error = simple_setattr(dentry, attr); 251 252 if (!error) { 253 fsnotify_change(dentry, ia_valid); 254 ima_inode_post_setattr(dentry); 255 evm_inode_post_setattr(dentry, ia_valid); 256 } 257 258 return error; 259 } 260 EXPORT_SYMBOL(notify_change); 261