attr.c

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    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 #include <linux/ima.h>
   18 
   19 /**
   20  * inode_change_ok - check if attribute changes to an inode are allowed
   21  * @inode:      inode to check
   22  * @attr:       attributes to change
   23  *
   24  * Check if we are allowed to change the attributes contained in @attr
   25  * in the given inode.  This includes the normal unix access permission
   26  * checks, as well as checks for rlimits and others.
   27  *
   28  * Should be called as the first thing in ->setattr implementations,
   29  * possibly after taking additional locks.
   30  */
   31 int inode_change_ok(const struct inode *inode, struct iattr *attr)
   32 {
   33         unsigned int ia_valid = attr->ia_valid;
   34 
   35         /*
   36          * First check size constraints.  These can't be overriden using
   37          * ATTR_FORCE.
   38          */
   39         if (ia_valid & ATTR_SIZE) {
   40                 int error = inode_newsize_ok(inode, attr->ia_size);
   41                 if (error)
   42                         return error;
   43         }
   44 
   45         /* If force is set do it anyway. */
   46         if (ia_valid & ATTR_FORCE)
   47                 return 0;
   48 
   49         /* Make sure a caller can chown. */
   50         if ((ia_valid & ATTR_UID) &&
   51             (!uid_eq(current_fsuid(), inode->i_uid) ||
   52              !uid_eq(attr->ia_uid, inode->i_uid)) &&
   53             !inode_capable(inode, CAP_CHOWN))
   54                 return -EPERM;
   55 
   56         /* Make sure caller can chgrp. */
   57         if ((ia_valid & ATTR_GID) &&
   58             (!uid_eq(current_fsuid(), inode->i_uid) ||
   59             (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
   60             !inode_capable(inode, CAP_CHOWN))
   61                 return -EPERM;
   62 
   63         /* Make sure a caller can chmod. */
   64         if (ia_valid & ATTR_MODE) {
   65                 if (!inode_owner_or_capable(inode))
   66                         return -EPERM;
   67                 /* Also check the setgid bit! */
   68                 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
   69                                 inode->i_gid) &&
   70                     !inode_capable(inode, CAP_FSETID))
   71                         attr->ia_mode &= ~S_ISGID;
   72         }
   73 
   74         /* Check for setting the inode time. */
   75         if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
   76                 if (!inode_owner_or_capable(inode))
   77                         return -EPERM;
   78         }
   79 
   80         return 0;
   81 }
   82 EXPORT_SYMBOL(inode_change_ok);
   83 
   84 /**
   85  * inode_newsize_ok - may this inode be truncated to a given size
   86  * @inode:      the inode to be truncated
   87  * @offset:     the new size to assign to the inode
   88  * @Returns:    0 on success, -ve errno on failure
   89  *
   90  * inode_newsize_ok must be called with i_mutex held.
   91  *
   92  * inode_newsize_ok will check filesystem limits and ulimits to check that the
   93  * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
   94  * when necessary. Caller must not proceed with inode size change if failure is
   95  * returned. @inode must be a file (not directory), with appropriate
   96  * permissions to allow truncate (inode_newsize_ok does NOT check these
   97  * conditions).
   98  */
   99 int inode_newsize_ok(const struct inode *inode, loff_t offset)
  100 {
  101         if (inode->i_size < offset) {
  102                 unsigned long limit;
  103 
  104                 limit = rlimit(RLIMIT_FSIZE);
  105                 if (limit != RLIM_INFINITY && offset > limit)
  106                         goto out_sig;
  107                 if (offset > inode->i_sb->s_maxbytes)
  108                         goto out_big;
  109         } else {
  110                 /*
  111                  * truncation of in-use swapfiles is disallowed - it would
  112                  * cause subsequent swapout to scribble on the now-freed
  113                  * blocks.
  114                  */
  115                 if (IS_SWAPFILE(inode))
  116                         return -ETXTBSY;
  117         }
  118 
  119         return 0;
  120 out_sig:
  121         send_sig(SIGXFSZ, current, 0);
  122 out_big:
  123         return -EFBIG;
  124 }
  125 EXPORT_SYMBOL(inode_newsize_ok);
  126 
  127 /**
  128  * setattr_copy - copy simple metadata updates into the generic inode
  129  * @inode:      the inode to be updated
  130  * @attr:       the new attributes
  131  *
  132  * setattr_copy must be called with i_mutex held.
  133  *
  134  * setattr_copy updates the inode's metadata with that specified
  135  * in attr. Noticeably missing is inode size update, which is more complex
  136  * as it requires pagecache updates.
  137  *
  138  * The inode is not marked as dirty after this operation. The rationale is
  139  * that for "simple" filesystems, the struct inode is the inode storage.
  140  * The caller is free to mark the inode dirty afterwards if needed.
  141  */
  142 void setattr_copy(struct inode *inode, const struct iattr *attr)
  143 {
  144         unsigned int ia_valid = attr->ia_valid;
  145 
  146         if (ia_valid & ATTR_UID)
  147                 inode->i_uid = attr->ia_uid;
  148         if (ia_valid & ATTR_GID)
  149                 inode->i_gid = attr->ia_gid;
  150         if (ia_valid & ATTR_ATIME)
  151                 inode->i_atime = timespec_trunc(attr->ia_atime,
  152                                                 inode->i_sb->s_time_gran);
  153         if (ia_valid & ATTR_MTIME)
  154                 inode->i_mtime = timespec_trunc(attr->ia_mtime,
  155                                                 inode->i_sb->s_time_gran);
  156         if (ia_valid & ATTR_CTIME)
  157                 inode->i_ctime = timespec_trunc(attr->ia_ctime,
  158                                                 inode->i_sb->s_time_gran);
  159         if (ia_valid & ATTR_MODE) {
  160                 umode_t mode = attr->ia_mode;
  161 
  162                 if (!in_group_p(inode->i_gid) &&
  163                     !inode_capable(inode, CAP_FSETID))
  164                         mode &= ~S_ISGID;
  165                 inode->i_mode = mode;
  166         }
  167 }
  168 EXPORT_SYMBOL(setattr_copy);
  169 
  170 int notify_change(struct dentry * dentry, struct iattr * attr)
  171 {
  172         struct inode *inode = dentry->d_inode;
  173         umode_t mode = inode->i_mode;
  174         int error;
  175         struct timespec now;
  176         unsigned int ia_valid = attr->ia_valid;
  177 
  178         WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
  179 
  180         if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
  181                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  182                         return -EPERM;
  183         }
  184 
  185         if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
  186                 if (attr->ia_size != inode->i_size)
  187                         inode_inc_iversion(inode);
  188         }
  189 
  190         if ((ia_valid & ATTR_MODE)) {
  191                 umode_t amode = attr->ia_mode;
  192                 /* Flag setting protected by i_mutex */
  193                 if (is_sxid(amode))
  194                         inode->i_flags &= ~S_NOSEC;
  195         }
  196 
  197         now = current_fs_time(inode->i_sb);
  198 
  199         attr->ia_ctime = now;
  200         if (!(ia_valid & ATTR_ATIME_SET))
  201                 attr->ia_atime = now;
  202         if (!(ia_valid & ATTR_MTIME_SET))
  203                 attr->ia_mtime = now;
  204         if (ia_valid & ATTR_KILL_PRIV) {
  205                 attr->ia_valid &= ~ATTR_KILL_PRIV;
  206                 ia_valid &= ~ATTR_KILL_PRIV;
  207                 error = security_inode_need_killpriv(dentry);
  208                 if (error > 0)
  209                         error = security_inode_killpriv(dentry);
  210                 if (error)
  211                         return error;
  212         }
  213 
  214         /*
  215          * We now pass ATTR_KILL_S*ID to the lower level setattr function so
  216          * that the function has the ability to reinterpret a mode change
  217          * that's due to these bits. This adds an implicit restriction that
  218          * no function will ever call notify_change with both ATTR_MODE and
  219          * ATTR_KILL_S*ID set.
  220          */
  221         if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
  222             (ia_valid & ATTR_MODE))
  223                 BUG();
  224 
  225         if (ia_valid & ATTR_KILL_SUID) {
  226                 if (mode & S_ISUID) {
  227                         ia_valid = attr->ia_valid |= ATTR_MODE;
  228                         attr->ia_mode = (inode->i_mode & ~S_ISUID);
  229                 }
  230         }
  231         if (ia_valid & ATTR_KILL_SGID) {
  232                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
  233                         if (!(ia_valid & ATTR_MODE)) {
  234                                 ia_valid = attr->ia_valid |= ATTR_MODE;
  235                                 attr->ia_mode = inode->i_mode;
  236                         }
  237                         attr->ia_mode &= ~S_ISGID;
  238                 }
  239         }
  240         if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
  241                 return 0;
  242 
  243         error = security_inode_setattr(dentry, attr);
  244         if (error)
  245                 return error;
  246 
  247         if (inode->i_op->setattr)
  248                 error = inode->i_op->setattr(dentry, attr);
  249         else
  250                 error = simple_setattr(dentry, attr);
  251 
  252         if (!error) {
  253                 fsnotify_change(dentry, ia_valid);
  254                 ima_inode_post_setattr(dentry);
  255                 evm_inode_post_setattr(dentry, ia_valid);
  256         }
  257 
  258         return error;
  259 }
  260 EXPORT_SYMBOL(notify_change);

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FreeBSD/Linux Kernel Cross Reference sys/fs/attr.c

FreeBSD/Linux Kernel Cross Reference
sys/fs/attr.c