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/module.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 17 /** 18 * inode_change_ok - check if attribute changes to an inode are allowed 19 * @inode: inode to check 20 * @attr: attributes to change 21 * 22 * Check if we are allowed to change the attributes contained in @attr 23 * in the given inode. This includes the normal unix access permission 24 * checks, as well as checks for rlimits and others. 25 * 26 * Should be called as the first thing in ->setattr implementations, 27 * possibly after taking additional locks. 28 */ 29 int inode_change_ok(const struct inode *inode, struct iattr *attr) 30 { 31 unsigned int ia_valid = attr->ia_valid; 32 33 /* 34 * First check size constraints. These can't be overriden using 35 * ATTR_FORCE. 36 */ 37 if (ia_valid & ATTR_SIZE) { 38 int error = inode_newsize_ok(inode, attr->ia_size); 39 if (error) 40 return error; 41 } 42 43 /* If force is set do it anyway. */ 44 if (ia_valid & ATTR_FORCE) 45 return 0; 46 47 /* Make sure a caller can chown. */ 48 if ((ia_valid & ATTR_UID) && 49 (current_fsuid() != inode->i_uid || 50 attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN)) 51 return -EPERM; 52 53 /* Make sure caller can chgrp. */ 54 if ((ia_valid & ATTR_GID) && 55 (current_fsuid() != inode->i_uid || 56 (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) && 57 !capable(CAP_CHOWN)) 58 return -EPERM; 59 60 /* Make sure a caller can chmod. */ 61 if (ia_valid & ATTR_MODE) { 62 if (!is_owner_or_cap(inode)) 63 return -EPERM; 64 /* Also check the setgid bit! */ 65 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : 66 inode->i_gid) && !capable(CAP_FSETID)) 67 attr->ia_mode &= ~S_ISGID; 68 } 69 70 /* Check for setting the inode time. */ 71 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { 72 if (!is_owner_or_cap(inode)) 73 return -EPERM; 74 } 75 76 return 0; 77 } 78 EXPORT_SYMBOL(inode_change_ok); 79 80 /** 81 * inode_newsize_ok - may this inode be truncated to a given size 82 * @inode: the inode to be truncated 83 * @offset: the new size to assign to the inode 84 * @Returns: 0 on success, -ve errno on failure 85 * 86 * inode_newsize_ok must be called with i_mutex held. 87 * 88 * inode_newsize_ok will check filesystem limits and ulimits to check that the 89 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ 90 * when necessary. Caller must not proceed with inode size change if failure is 91 * returned. @inode must be a file (not directory), with appropriate 92 * permissions to allow truncate (inode_newsize_ok does NOT check these 93 * conditions). 94 */ 95 int inode_newsize_ok(const struct inode *inode, loff_t offset) 96 { 97 if (inode->i_size < offset) { 98 unsigned long limit; 99 100 limit = rlimit(RLIMIT_FSIZE); 101 if (limit != RLIM_INFINITY && offset > limit) 102 goto out_sig; 103 if (offset > inode->i_sb->s_maxbytes) 104 goto out_big; 105 } else { 106 /* 107 * truncation of in-use swapfiles is disallowed - it would 108 * cause subsequent swapout to scribble on the now-freed 109 * blocks. 110 */ 111 if (IS_SWAPFILE(inode)) 112 return -ETXTBSY; 113 } 114 115 return 0; 116 out_sig: 117 send_sig(SIGXFSZ, current, 0); 118 out_big: 119 return -EFBIG; 120 } 121 EXPORT_SYMBOL(inode_newsize_ok); 122 123 /** 124 * setattr_copy - copy simple metadata updates into the generic inode 125 * @inode: the inode to be updated 126 * @attr: the new attributes 127 * 128 * setattr_copy must be called with i_mutex held. 129 * 130 * setattr_copy updates the inode's metadata with that specified 131 * in attr. Noticably missing is inode size update, which is more complex 132 * as it requires pagecache updates. 133 * 134 * The inode is not marked as dirty after this operation. The rationale is 135 * that for "simple" filesystems, the struct inode is the inode storage. 136 * The caller is free to mark the inode dirty afterwards if needed. 137 */ 138 void setattr_copy(struct inode *inode, const struct iattr *attr) 139 { 140 unsigned int ia_valid = attr->ia_valid; 141 142 if (ia_valid & ATTR_UID) 143 inode->i_uid = attr->ia_uid; 144 if (ia_valid & ATTR_GID) 145 inode->i_gid = attr->ia_gid; 146 if (ia_valid & ATTR_ATIME) 147 inode->i_atime = timespec_trunc(attr->ia_atime, 148 inode->i_sb->s_time_gran); 149 if (ia_valid & ATTR_MTIME) 150 inode->i_mtime = timespec_trunc(attr->ia_mtime, 151 inode->i_sb->s_time_gran); 152 if (ia_valid & ATTR_CTIME) 153 inode->i_ctime = timespec_trunc(attr->ia_ctime, 154 inode->i_sb->s_time_gran); 155 if (ia_valid & ATTR_MODE) { 156 umode_t mode = attr->ia_mode; 157 158 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID)) 159 mode &= ~S_ISGID; 160 inode->i_mode = mode; 161 } 162 } 163 EXPORT_SYMBOL(setattr_copy); 164 165 int notify_change(struct dentry * dentry, struct iattr * attr) 166 { 167 struct inode *inode = dentry->d_inode; 168 mode_t mode = inode->i_mode; 169 int error; 170 struct timespec now; 171 unsigned int ia_valid = attr->ia_valid; 172 173 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { 174 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 175 return -EPERM; 176 } 177 178 now = current_fs_time(inode->i_sb); 179 180 attr->ia_ctime = now; 181 if (!(ia_valid & ATTR_ATIME_SET)) 182 attr->ia_atime = now; 183 if (!(ia_valid & ATTR_MTIME_SET)) 184 attr->ia_mtime = now; 185 if (ia_valid & ATTR_KILL_PRIV) { 186 attr->ia_valid &= ~ATTR_KILL_PRIV; 187 ia_valid &= ~ATTR_KILL_PRIV; 188 error = security_inode_need_killpriv(dentry); 189 if (error > 0) 190 error = security_inode_killpriv(dentry); 191 if (error) 192 return error; 193 } 194 195 /* 196 * We now pass ATTR_KILL_S*ID to the lower level setattr function so 197 * that the function has the ability to reinterpret a mode change 198 * that's due to these bits. This adds an implicit restriction that 199 * no function will ever call notify_change with both ATTR_MODE and 200 * ATTR_KILL_S*ID set. 201 */ 202 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && 203 (ia_valid & ATTR_MODE)) 204 BUG(); 205 206 if (ia_valid & ATTR_KILL_SUID) { 207 if (mode & S_ISUID) { 208 ia_valid = attr->ia_valid |= ATTR_MODE; 209 attr->ia_mode = (inode->i_mode & ~S_ISUID); 210 } 211 } 212 if (ia_valid & ATTR_KILL_SGID) { 213 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 214 if (!(ia_valid & ATTR_MODE)) { 215 ia_valid = attr->ia_valid |= ATTR_MODE; 216 attr->ia_mode = inode->i_mode; 217 } 218 attr->ia_mode &= ~S_ISGID; 219 } 220 } 221 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) 222 return 0; 223 224 error = security_inode_setattr(dentry, attr); 225 if (error) 226 return error; 227 228 if (ia_valid & ATTR_SIZE) 229 down_write(&dentry->d_inode->i_alloc_sem); 230 231 if (inode->i_op->setattr) 232 error = inode->i_op->setattr(dentry, attr); 233 else 234 error = simple_setattr(dentry, attr); 235 236 if (ia_valid & ATTR_SIZE) 237 up_write(&dentry->d_inode->i_alloc_sem); 238 239 if (!error) 240 fsnotify_change(dentry, ia_valid); 241 242 return error; 243 } 244 245 EXPORT_SYMBOL(notify_change); 246