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