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(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
  64 EXPORT_SYMBOL(inode_change_ok);
  65
  66 int inode_setattr(struct inode * inode, struct iattr * attr)
  67 {
  68         unsigned int ia_valid = attr->ia_valid;
  69
  70         if (ia_valid & ATTR_SIZE &&
  71             attr->ia_size != i_size_read(inode)) {
  72                 int error = vmtruncate(inode, attr->ia_size);
  73                 if (error)
  74                         return error;
  75         }
  76
  77         if (ia_valid & ATTR_UID)
  78                 inode->i_uid = attr->ia_uid;
  79         if (ia_valid & ATTR_GID)
  80                 inode->i_gid = attr->ia_gid;
  81         if (ia_valid & ATTR_ATIME)
  82                 inode->i_atime = timespec_trunc(attr->ia_atime,
  83                                                 inode->i_sb->s_time_gran);
  84         if (ia_valid & ATTR_MTIME)
  85                 inode->i_mtime = timespec_trunc(attr->ia_mtime,
  86                                                 inode->i_sb->s_time_gran);
  87         if (ia_valid & ATTR_CTIME)
  88                 inode->i_ctime = timespec_trunc(attr->ia_ctime,
  89                                                 inode->i_sb->s_time_gran);
  90         if (ia_valid & ATTR_MODE) {
  91                 umode_t mode = attr->ia_mode;
  92
  93                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
  94                         mode &= ~S_ISGID;
  95                 inode->i_mode = mode;
  96         }
  97         mark_inode_dirty(inode);
  98
  99         return 0;
 100 }
 101 EXPORT_SYMBOL(inode_setattr);
 102
 103 int notify_change(struct dentry * dentry, struct iattr * attr)
 104 {
 105         struct inode *inode = dentry->d_inode;
 106         mode_t mode = inode->i_mode;
 107         int error;
 108         struct timespec now;
 109         unsigned int ia_valid = attr->ia_valid;
 110
 111         if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
 112                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 113                         return -EPERM;
 114         }
 115
 116         now = current_fs_time(inode->i_sb);
 117
 118         attr->ia_ctime = now;
 119         if (!(ia_valid & ATTR_ATIME_SET))
 120                 attr->ia_atime = now;
 121         if (!(ia_valid & ATTR_MTIME_SET))
 122                 attr->ia_mtime = now;
 123         if (ia_valid & ATTR_KILL_PRIV) {
 124                 attr->ia_valid &= ~ATTR_KILL_PRIV;
 125                 ia_valid &= ~ATTR_KILL_PRIV;
 126                 error = security_inode_need_killpriv(dentry);
 127                 if (error > 0)
 128                         error = security_inode_killpriv(dentry);
 129                 if (error)
 130                         return error;
 131         }
 132
 133         /*
 134          * We now pass ATTR_KILL_S*ID to the lower level setattr function so
 135          * that the function has the ability to reinterpret a mode change
 136          * that's due to these bits. This adds an implicit restriction that
 137          * no function will ever call notify_change with both ATTR_MODE and
 138          * ATTR_KILL_S*ID set.
 139          */
 140         if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
 141             (ia_valid & ATTR_MODE))
 142                 BUG();
 143
 144         if (ia_valid & ATTR_KILL_SUID) {
 145                 if (mode & S_ISUID) {
 146                         ia_valid = attr->ia_valid |= ATTR_MODE;
 147                         attr->ia_mode = (inode->i_mode & ~S_ISUID);
 148                 }
 149         }
 150         if (ia_valid & ATTR_KILL_SGID) {
 151                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
 152                         if (!(ia_valid & ATTR_MODE)) {
 153                                 ia_valid = attr->ia_valid |= ATTR_MODE;
 154                                 attr->ia_mode = inode->i_mode;
 155                         }
 156                         attr->ia_mode &= ~S_ISGID;
 157                 }
 158         }
 159         if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
 160                 return 0;
 161
 162         error = security_inode_setattr(dentry, attr);
 163         if (error)
 164                 return error;
 165
 166         if (ia_valid & ATTR_SIZE)
 167                 down_write(&dentry->d_inode->i_alloc_sem);
 168
 169         if (inode->i_op && inode->i_op->setattr) {
 170                 error = inode->i_op->setattr(dentry, attr);
 171         } else {
 172                 error = inode_change_ok(inode, attr);
 173                 if (!error) {
 174                         if ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
 175                             (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid))
 176                                 error = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
 177                         if (!error)
 178                                 error = inode_setattr(inode, attr);
 179                 }
 180         }
 181
 182         if (ia_valid & ATTR_SIZE)
 183                 up_write(&dentry->d_inode->i_alloc_sem);
 184
 185         if (!error)
 186                 fsnotify_change(dentry, ia_valid);
 187
 188         return error;
 189 }
 190
 191 EXPORT_SYMBOL(notify_change);