279 lines
7.9 KiB
C
279 lines
7.9 KiB
C
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/*
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* linux/fs/attr.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* changes by Thomas Schoebel-Theuer
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*/
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#include <linux/export.h>
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#include <linux/time.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/capability.h>
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#include <linux/fsnotify.h>
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#include <linux/fcntl.h>
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#include <linux/security.h>
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#include <linux/evm.h>
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#include <linux/ima.h>
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/**
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* inode_change_ok - check if attribute changes to an inode are allowed
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* @inode: inode to check
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* @attr: attributes to change
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*
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* Check if we are allowed to change the attributes contained in @attr
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* in the given inode. This includes the normal unix access permission
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* checks, as well as checks for rlimits and others.
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*
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* Should be called as the first thing in ->setattr implementations,
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* possibly after taking additional locks.
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*/
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int inode_change_ok(const struct inode *inode, struct iattr *attr)
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{
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unsigned int ia_valid = attr->ia_valid;
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/*
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* First check size constraints. These can't be overriden using
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* ATTR_FORCE.
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*/
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if (ia_valid & ATTR_SIZE) {
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int error = inode_newsize_ok(inode, attr->ia_size);
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if (error)
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return error;
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}
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/* If force is set do it anyway. */
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if (ia_valid & ATTR_FORCE)
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return 0;
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/* Make sure a caller can chown. */
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if ((ia_valid & ATTR_UID) &&
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(!uid_eq(current_fsuid(), inode->i_uid) ||
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!uid_eq(attr->ia_uid, inode->i_uid)) &&
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!capable_wrt_inode_uidgid(inode, CAP_CHOWN))
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return -EPERM;
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/* Make sure caller can chgrp. */
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if ((ia_valid & ATTR_GID) &&
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(!uid_eq(current_fsuid(), inode->i_uid) ||
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(!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
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!capable_wrt_inode_uidgid(inode, CAP_CHOWN))
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return -EPERM;
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/* Make sure a caller can chmod. */
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if (ia_valid & ATTR_MODE) {
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if (!inode_owner_or_capable(inode))
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return -EPERM;
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/* Also check the setgid bit! */
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if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
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inode->i_gid) &&
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!capable_wrt_inode_uidgid(inode, CAP_FSETID))
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attr->ia_mode &= ~S_ISGID;
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}
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/* Check for setting the inode time. */
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if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
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if (!inode_owner_or_capable(inode))
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return -EPERM;
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}
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return 0;
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}
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EXPORT_SYMBOL(inode_change_ok);
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/**
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* inode_newsize_ok - may this inode be truncated to a given size
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* @inode: the inode to be truncated
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* @offset: the new size to assign to the inode
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* @Returns: 0 on success, -ve errno on failure
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*
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* inode_newsize_ok must be called with i_mutex held.
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*
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* inode_newsize_ok will check filesystem limits and ulimits to check that the
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* new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
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* when necessary. Caller must not proceed with inode size change if failure is
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* returned. @inode must be a file (not directory), with appropriate
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* permissions to allow truncate (inode_newsize_ok does NOT check these
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* conditions).
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*/
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int inode_newsize_ok(const struct inode *inode, loff_t offset)
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{
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if (inode->i_size < offset) {
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unsigned long limit;
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limit = rlimit(RLIMIT_FSIZE);
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if (limit != RLIM_INFINITY && offset > limit)
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goto out_sig;
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if (offset > inode->i_sb->s_maxbytes)
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goto out_big;
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} else {
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/*
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* truncation of in-use swapfiles is disallowed - it would
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* cause subsequent swapout to scribble on the now-freed
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* blocks.
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*/
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if (IS_SWAPFILE(inode))
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return -ETXTBSY;
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}
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return 0;
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out_sig:
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send_sig(SIGXFSZ, current, 0);
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out_big:
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return -EFBIG;
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}
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EXPORT_SYMBOL(inode_newsize_ok);
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/**
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* setattr_copy - copy simple metadata updates into the generic inode
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* @inode: the inode to be updated
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* @attr: the new attributes
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*
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* setattr_copy must be called with i_mutex held.
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*
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* setattr_copy updates the inode's metadata with that specified
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* in attr. Noticeably missing is inode size update, which is more complex
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* as it requires pagecache updates.
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*
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* The inode is not marked as dirty after this operation. The rationale is
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* that for "simple" filesystems, the struct inode is the inode storage.
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* The caller is free to mark the inode dirty afterwards if needed.
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*/
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void setattr_copy(struct inode *inode, const struct iattr *attr)
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{
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unsigned int ia_valid = attr->ia_valid;
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if (ia_valid & ATTR_UID)
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inode->i_uid = attr->ia_uid;
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if (ia_valid & ATTR_GID)
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inode->i_gid = attr->ia_gid;
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if (ia_valid & ATTR_ATIME)
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inode->i_atime = timespec_trunc(attr->ia_atime,
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inode->i_sb->s_time_gran);
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if (ia_valid & ATTR_MTIME)
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inode->i_mtime = timespec_trunc(attr->ia_mtime,
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inode->i_sb->s_time_gran);
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if (ia_valid & ATTR_CTIME)
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inode->i_ctime = timespec_trunc(attr->ia_ctime,
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inode->i_sb->s_time_gran);
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if (ia_valid & ATTR_MODE) {
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umode_t mode = attr->ia_mode;
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if (!in_group_p(inode->i_gid) &&
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!capable_wrt_inode_uidgid(inode, CAP_FSETID))
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mode &= ~S_ISGID;
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inode->i_mode = mode;
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}
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}
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EXPORT_SYMBOL(setattr_copy);
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/**
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* notify_change - modify attributes of a filesytem object
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* @dentry: object affected
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* @iattr: new attributes
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* @delegated_inode: returns inode, if the inode is delegated
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*
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* The caller must hold the i_mutex on the affected object.
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*
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* If notify_change discovers a delegation in need of breaking,
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* it will return -EWOULDBLOCK and return a reference to the inode in
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* delegated_inode. The caller should then break the delegation and
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* retry. Because breaking a delegation may take a long time, the
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* caller should drop the i_mutex before doing so.
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*
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* Alternatively, a caller may pass NULL for delegated_inode. This may
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* be appropriate for callers that expect the underlying filesystem not
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* to be NFS exported. Also, passing NULL is fine for callers holding
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* the file open for write, as there can be no conflicting delegation in
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* that case.
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*/
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int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
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{
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struct inode *inode = dentry->d_inode;
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umode_t mode = inode->i_mode;
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int error;
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struct timespec now;
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unsigned int ia_valid = attr->ia_valid;
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WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
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if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
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if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
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return -EPERM;
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}
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if ((ia_valid & ATTR_MODE)) {
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umode_t amode = attr->ia_mode;
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/* Flag setting protected by i_mutex */
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if (is_sxid(amode))
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inode->i_flags &= ~S_NOSEC;
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}
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now = current_fs_time(inode->i_sb);
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attr->ia_ctime = now;
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if (!(ia_valid & ATTR_ATIME_SET))
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attr->ia_atime = now;
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if (!(ia_valid & ATTR_MTIME_SET))
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attr->ia_mtime = now;
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if (ia_valid & ATTR_KILL_PRIV) {
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attr->ia_valid &= ~ATTR_KILL_PRIV;
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ia_valid &= ~ATTR_KILL_PRIV;
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error = security_inode_need_killpriv(dentry);
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if (error > 0)
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error = security_inode_killpriv(dentry);
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if (error)
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return error;
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}
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/*
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* We now pass ATTR_KILL_S*ID to the lower level setattr function so
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* that the function has the ability to reinterpret a mode change
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* that's due to these bits. This adds an implicit restriction that
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* no function will ever call notify_change with both ATTR_MODE and
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* ATTR_KILL_S*ID set.
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*/
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if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
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(ia_valid & ATTR_MODE))
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BUG();
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if (ia_valid & ATTR_KILL_SUID) {
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if (mode & S_ISUID) {
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ia_valid = attr->ia_valid |= ATTR_MODE;
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attr->ia_mode = (inode->i_mode & ~S_ISUID);
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}
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}
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if (ia_valid & ATTR_KILL_SGID) {
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if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
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if (!(ia_valid & ATTR_MODE)) {
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ia_valid = attr->ia_valid |= ATTR_MODE;
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attr->ia_mode = inode->i_mode;
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}
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attr->ia_mode &= ~S_ISGID;
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}
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}
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if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
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return 0;
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error = security_inode_setattr(dentry, attr);
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if (error)
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return error;
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error = try_break_deleg(inode, delegated_inode);
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if (error)
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return error;
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if (inode->i_op->setattr)
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error = inode->i_op->setattr(dentry, attr);
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else
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error = simple_setattr(dentry, attr);
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if (!error) {
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fsnotify_change(dentry, ia_valid);
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ima_inode_post_setattr(dentry);
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evm_inode_post_setattr(dentry, ia_valid);
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}
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return error;
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}
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EXPORT_SYMBOL(notify_change);
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