fs/attr.c

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