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 (current_fsuid() != inode->i_uid || 51 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 (current_fsuid() != inode->i_uid || 57 (!in_group_p(attr->ia_gid) && 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 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { 175 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 176 return -EPERM; 177 } 178 179 if ((ia_valid & ATTR_MODE)) { 180 umode_t amode = attr->ia_mode; 181 /* Flag setting protected by i_mutex */ 182 if (is_sxid(amode)) 183 inode->i_flags &= ~S_NOSEC; 184 } 185 186 now = current_fs_time(inode->i_sb); 187 188 attr->ia_ctime = now; 189 if (!(ia_valid & ATTR_ATIME_SET)) 190 attr->ia_atime = now; 191 if (!(ia_valid & ATTR_MTIME_SET)) 192 attr->ia_mtime = now; 193 if (ia_valid & ATTR_KILL_PRIV) { 194 attr->ia_valid &= ~ATTR_KILL_PRIV; 195 ia_valid &= ~ATTR_KILL_PRIV; 196 error = security_inode_need_killpriv(dentry); 197 if (error > 0) 198 error = security_inode_killpriv(dentry); 199 if (error) 200 return error; 201 } 202 203 /* 204 * We now pass ATTR_KILL_S*ID to the lower level setattr function so 205 * that the function has the ability to reinterpret a mode change 206 * that's due to these bits. This adds an implicit restriction that 207 * no function will ever call notify_change with both ATTR_MODE and 208 * ATTR_KILL_S*ID set. 209 */ 210 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && 211 (ia_valid & ATTR_MODE)) 212 BUG(); 213 214 if (ia_valid & ATTR_KILL_SUID) { 215 if (mode & S_ISUID) { 216 ia_valid = attr->ia_valid |= ATTR_MODE; 217 attr->ia_mode = (inode->i_mode & ~S_ISUID); 218 } 219 } 220 if (ia_valid & ATTR_KILL_SGID) { 221 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 222 if (!(ia_valid & ATTR_MODE)) { 223 ia_valid = attr->ia_valid |= ATTR_MODE; 224 attr->ia_mode = inode->i_mode; 225 } 226 attr->ia_mode &= ~S_ISGID; 227 } 228 } 229 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) 230 return 0; 231 232 error = security_inode_setattr(dentry, attr); 233 if (error) 234 return error; 235 236 if (inode->i_op->setattr) 237 error = inode->i_op->setattr(dentry, attr); 238 else 239 error = simple_setattr(dentry, attr); 240 241 if (!error) { 242 fsnotify_change(dentry, ia_valid); 243 evm_inode_post_setattr(dentry, ia_valid); 244 } 245 246 return error; 247 } 248 249 EXPORT_SYMBOL(notify_change); 250