attr.c

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/*
 *  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/capability.h>
#include <linux/fsnotify.h>
#include <linux/fcntl.h>
#include <linux/security.h>
#include <linux/evm.h>
#include <linux/ima.h>

int inode_change_ok(const struct inode *inode, struct iattr *attr)
{
    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)
        return 0;

    /* Make sure a caller can chown. */
    if ((ia_valid & ATTR_UID) &&
        (!uid_eq(current_fsuid(), inode->i_uid) ||
         !uid_eq(attr->ia_uid, inode->i_uid)) && !capable(CAP_CHOWN))
        return -EPERM;

    /* Make sure caller can chgrp. */
    if ((ia_valid & ATTR_GID) &&
        (!uid_eq(current_fsuid(), inode->i_uid) ||
        (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
        !capable(CAP_CHOWN))
        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! */
        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 (!inode_owner_or_capable(inode))
            return -EPERM;
    }

    return 0;
}
EXPORT_SYMBOL(inode_change_ok);

int inode_newsize_ok(const struct inode *inode, loff_t offset)
{
    if (inode->i_size < offset) {
        unsigned long limit;

        limit = rlimit(RLIMIT_FSIZE);
        if (limit != RLIM_INFINITY && offset > limit)
            goto out_sig;
        if (offset > inode->i_sb->s_maxbytes)
            goto out_big;
    } else {
        /*
         * truncation of in-use swapfiles is disallowed - it would
         * cause subsequent swapout to scribble on the now-freed
         * blocks.
         */
        if (IS_SWAPFILE(inode))
            return -ETXTBSY;
    }

    return 0;
out_sig:
    send_sig(SIGXFSZ, current, 0);
out_big:
    return -EFBIG;
}
EXPORT_SYMBOL(inode_newsize_ok);

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

    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;
    }
}
EXPORT_SYMBOL(setattr_copy);

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

    WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));

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

    if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
        if (attr->ia_size != inode->i_size)
            inode_inc_iversion(inode);
    }

    if ((ia_valid & ATTR_MODE)) {
        umode_t amode = attr->ia_mode;
        /* Flag setting protected by i_mutex */
        if (is_sxid(amode))
            inode->i_flags &= ~S_NOSEC;
    }

    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;

    error = security_inode_setattr(dentry, attr);
    if (error)
        return error;

    if (inode->i_op->setattr)
        error = inode->i_op->setattr(dentry, attr);
    else
        error = simple_setattr(dentry, attr);

    if (!error) {
        fsnotify_change(dentry, ia_valid);
        ima_inode_post_setattr(dentry);
        evm_inode_post_setattr(dentry, ia_valid);
    }

    return error;
}
EXPORT_SYMBOL(notify_change);