root/fs/attr.c

DEFINITIONS

1. inode_change_ok
2. inode_setattr
3. notify_change

/*
 *  linux/fs/attr.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  changes by Thomas Schoebel-Theuer
 */

#include <linux/module.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/capability.h>
#include <linux/fsnotify.h>
#include <linux/fcntl.h>
#include <linux/quotaops.h>
#include <linux/security.h>

/* Taken over from the old code... */

/* POSIX UID/GID verification for setting inode attributes. */
int inode_change_ok(struct inode *inode, struct iattr *attr)
{
        int retval = -EPERM;
        unsigned int ia_valid = attr->ia_valid;

        /* If force is set do it anyway. */
        if (ia_valid & ATTR_FORCE)
                goto fine;

        /* Make sure a caller can chown. */
        if ((ia_valid & ATTR_UID) &&
            (current->fsuid != inode->i_uid ||
             attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
                goto error;

        /* Make sure caller can chgrp. */
        if ((ia_valid & ATTR_GID) &&
            (current->fsuid != inode->i_uid ||
            (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
            !capable(CAP_CHOWN))
                goto error;

        /* Make sure a caller can chmod. */
        if (ia_valid & ATTR_MODE) {
                if (!is_owner_or_cap(inode))
                        goto error;
                /* Also check the setgid bit! */
                if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
                                inode->i_gid) && !capable(CAP_FSETID))
                        attr->ia_mode &= ~S_ISGID;
        }

        /* Check for setting the inode time. */
        if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
                if (!is_owner_or_cap(inode))
                        goto error;
        }
fine:
        retval = 0;
error:
        return retval;
}

EXPORT_SYMBOL(inode_change_ok);

int inode_setattr(struct inode * inode, struct iattr * attr)
{
        unsigned int ia_valid = attr->ia_valid;

        if (ia_valid & ATTR_SIZE &&
            attr->ia_size != i_size_read(inode)) {
                int error = vmtruncate(inode, attr->ia_size);
                if (error)
                        return error;
        }

        if (ia_valid & ATTR_UID)
                inode->i_uid = attr->ia_uid;
        if (ia_valid & ATTR_GID)
                inode->i_gid = attr->ia_gid;
        if (ia_valid & ATTR_ATIME)
                inode->i_atime = timespec_trunc(attr->ia_atime,
                                                inode->i_sb->s_time_gran);
        if (ia_valid & ATTR_MTIME)
                inode->i_mtime = timespec_trunc(attr->ia_mtime,
                                                inode->i_sb->s_time_gran);
        if (ia_valid & ATTR_CTIME)
                inode->i_ctime = timespec_trunc(attr->ia_ctime,
                                                inode->i_sb->s_time_gran);
        if (ia_valid & ATTR_MODE) {
                umode_t mode = attr->ia_mode;

                if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
                        mode &= ~S_ISGID;
                inode->i_mode = mode;
        }
        mark_inode_dirty(inode);

        return 0;
}
EXPORT_SYMBOL(inode_setattr);

int notify_change(struct dentry * dentry, struct iattr * attr)
{
        struct inode *inode = dentry->d_inode;
        mode_t mode = inode->i_mode;
        int error;
        struct timespec now;
        unsigned int ia_valid = attr->ia_valid;

        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                        return -EPERM;
        }

        now = current_fs_time(inode->i_sb);

        attr->ia_ctime = now;
        if (!(ia_valid & ATTR_ATIME_SET))
                attr->ia_atime = now;
        if (!(ia_valid & ATTR_MTIME_SET))
                attr->ia_mtime = now;
        if (ia_valid & ATTR_KILL_PRIV) {
                attr->ia_valid &= ~ATTR_KILL_PRIV;
                ia_valid &= ~ATTR_KILL_PRIV;
                error = security_inode_need_killpriv(dentry);
                if (error > 0)
                        error = security_inode_killpriv(dentry);
                if (error)
                        return error;
        }

        /*
         * We now pass ATTR_KILL_S*ID to the lower level setattr function so
         * that the function has the ability to reinterpret a mode change
         * that's due to these bits. This adds an implicit restriction that
         * no function will ever call notify_change with both ATTR_MODE and
         * ATTR_KILL_S*ID set.
         */
        if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
            (ia_valid & ATTR_MODE))
                BUG();

        if (ia_valid & ATTR_KILL_SUID) {
                if (mode & S_ISUID) {
                        ia_valid = attr->ia_valid |= ATTR_MODE;
                        attr->ia_mode = (inode->i_mode & ~S_ISUID);
                }
        }
        if (ia_valid & ATTR_KILL_SGID) {
                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
                        if (!(ia_valid & ATTR_MODE)) {
                                ia_valid = attr->ia_valid |= ATTR_MODE;
                                attr->ia_mode = inode->i_mode;
                        }
                        attr->ia_mode &= ~S_ISGID;
                }
        }
        if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
                return 0;

        if (ia_valid & ATTR_SIZE)
                down_write(&dentry->d_inode->i_alloc_sem);

        if (inode->i_op && inode->i_op->setattr) {
                error = security_inode_setattr(dentry, attr);
                if (!error)
                        error = inode->i_op->setattr(dentry, attr);
        } else {
                error = inode_change_ok(inode, attr);
                if (!error)
                        error = security_inode_setattr(dentry, attr);
                if (!error) {
                        if ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
                            (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid))
                                error = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
                        if (!error)
                                error = inode_setattr(inode, attr);
                }
        }

        if (ia_valid & ATTR_SIZE)
                up_write(&dentry->d_inode->i_alloc_sem);

        if (!error)
                fsnotify_change(dentry, ia_valid);

        return error;
}

EXPORT_SYMBOL(notify_change);