linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 *  linux/fs/attr.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 *  changes by Thomas Schoebel-Theuer

 */

​

#include <linux/export.h>

#include <linux/time.h>

#include <linux/mm.h>

#include <linux/string.h>

#include <linux/sched/signal.h>

#include <linux/capability.h>

#include <linux/fsnotify.h>

#include <linux/fcntl.h>

#include <linux/security.h>

#include <linux/evm.h>

#include <linux/ima.h>

​

static bool chown_ok(const struct inode *inode, kuid_t uid)

{

    if (uid_eq(current_fsuid(), inode->i_uid) &&

        uid_eq(uid, inode->i_uid))

        return true;

    if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))

        return true;

    if (uid_eq(inode->i_uid, INVALID_UID) &&

        ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))

        return true;

    return false;

}

​

static bool chgrp_ok(const struct inode *inode, kgid_t gid)

{

    if (uid_eq(current_fsuid(), inode->i_uid) &&

        (in_group_p(gid) || gid_eq(gid, inode->i_gid)))

        return true;

    if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))

        return true;

    if (gid_eq(inode->i_gid, INVALID_GID) &&

        ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))

        return true;

    return false;

}

​

/**

 * setattr_prepare - check if attribute changes to a dentry are allowed

 * @dentry: dentry to check

 * @attr:   attributes to change

 *

 * Check if we are allowed to change the attributes contained in @attr

 * in the given dentry.  This includes the normal unix access permission

 * checks, as well as checks for rlimits and others. The function also clears

 * SGID bit from mode if user is not allowed to set it. Also file capabilities

 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.

 *

 * Should be called as the first thing in ->setattr implementations,

 * possibly after taking additional locks.

 */

int setattr_prepare(struct dentry *dentry, struct iattr *attr)

{

    struct inode *inode = d_inode(dentry);

    unsigned int ia_valid = attr->ia_valid;

​

    /*

     * First check size constraints.  These can't be overriden using

     * ATTR_FORCE.

     */

    if (ia_valid & ATTR_SIZE) {

        int error = inode_newsize_ok(inode, attr->ia_size);

        if (error)

            return error;

    }

​

    /* If force is set do it anyway. */

    if (ia_valid & ATTR_FORCE)

        goto kill_priv;

​

    /* Make sure a caller can chown. */

    if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid))

        return -EPERM;

​

    /* Make sure caller can chgrp. */

    if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid))

        return -EPERM;

​

    /* Make sure a caller can chmod. */

    if (ia_valid & ATTR_MODE) {

        if (!inode_owner_or_capable(inode))

            return -EPERM;

        /* Also check the setgid bit! */