quota.c

Go to the documentation of this file.

/*
 * Quota code necessary even when VFS quota support is not compiled
 * into the kernel.  The interesting stuff is over in dquot.c, here
 * we have symbols for initial quotactl(2) handling, the sysctl(2)
 * variables, etc - things needed even when quota support disabled.
 */

#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/slab.h>
#include <asm/current.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/capability.h>
#include <linux/quotaops.h>
#include <linux/types.h>
#include <linux/writeback.h>

static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
                     qid_t id)
{
    switch (cmd) {
    /* these commands do not require any special privilegues */
    case Q_GETFMT:
    case Q_SYNC:
    case Q_GETINFO:
    case Q_XGETQSTAT:
    case Q_XQUOTASYNC:
        break;
    /* allow to query information for dquots we "own" */
    case Q_GETQUOTA:
    case Q_XGETQUOTA:
        if ((type == USRQUOTA && uid_eq(current_euid(), make_kuid(current_user_ns(), id))) ||
            (type == GRPQUOTA && in_egroup_p(make_kgid(current_user_ns(), id))))
            break;
        /*FALLTHROUGH*/
    default:
        if (!capable(CAP_SYS_ADMIN))
            return -EPERM;
    }

    return security_quotactl(cmd, type, id, sb);
}

static void quota_sync_one(struct super_block *sb, void *arg)
{
    if (sb->s_qcop && sb->s_qcop->quota_sync)
        sb->s_qcop->quota_sync(sb, *(int *)arg);
}

static int quota_sync_all(int type)
{
    int ret;

    if (type >= MAXQUOTAS)
        return -EINVAL;
    ret = security_quotactl(Q_SYNC, type, 0, NULL);
    if (!ret)
        iterate_supers(quota_sync_one, &type);
    return ret;
}

static int quota_quotaon(struct super_block *sb, int type, int cmd, qid_t id,
                 struct path *path)
{
    if (!sb->s_qcop->quota_on && !sb->s_qcop->quota_on_meta)
        return -ENOSYS;
    if (sb->s_qcop->quota_on_meta)
        return sb->s_qcop->quota_on_meta(sb, type, id);
    if (IS_ERR(path))
        return PTR_ERR(path);
    return sb->s_qcop->quota_on(sb, type, id, path);
}

static int quota_getfmt(struct super_block *sb, int type, void __user *addr)
{
    __u32 fmt;

    down_read(&sb_dqopt(sb)->dqptr_sem);
    if (!sb_has_quota_active(sb, type)) {
        up_read(&sb_dqopt(sb)->dqptr_sem);
        return -ESRCH;
    }
    fmt = sb_dqopt(sb)->info[type].dqi_format->qf_fmt_id;
    up_read(&sb_dqopt(sb)->dqptr_sem);
    if (copy_to_user(addr, &fmt, sizeof(fmt)))
        return -EFAULT;
    return 0;
}

static int quota_getinfo(struct super_block *sb, int type, void __user *addr)
{
    struct if_dqinfo info;
    int ret;

    if (!sb->s_qcop->get_info)
        return -ENOSYS;
    ret = sb->s_qcop->get_info(sb, type, &info);
    if (!ret && copy_to_user(addr, &info, sizeof(info)))
        return -EFAULT;
    return ret;
}

static int quota_setinfo(struct super_block *sb, int type, void __user *addr)
{
    struct if_dqinfo info;

    if (copy_from_user(&info, addr, sizeof(info)))
        return -EFAULT;
    if (!sb->s_qcop->set_info)
        return -ENOSYS;
    return sb->s_qcop->set_info(sb, type, &info);
}

static void copy_to_if_dqblk(struct if_dqblk *dst, struct fs_disk_quota *src)
{
    dst->dqb_bhardlimit = src->d_blk_hardlimit;
    dst->dqb_bsoftlimit = src->d_blk_softlimit;
    dst->dqb_curspace = src->d_bcount;
    dst->dqb_ihardlimit = src->d_ino_hardlimit;
    dst->dqb_isoftlimit = src->d_ino_softlimit;
    dst->dqb_curinodes = src->d_icount;
    dst->dqb_btime = src->d_btimer;
    dst->dqb_itime = src->d_itimer;
    dst->dqb_valid = QIF_ALL;
}

static int quota_getquota(struct super_block *sb, int type, qid_t id,
              void __user *addr)
{
    struct kqid qid;
    struct fs_disk_quota fdq;
    struct if_dqblk idq;
    int ret;

    if (!sb->s_qcop->get_dqblk)
        return -ENOSYS;
    qid = make_kqid(current_user_ns(), type, id);
    if (!qid_valid(qid))
        return -EINVAL;
    ret = sb->s_qcop->get_dqblk(sb, qid, &fdq);
    if (ret)
        return ret;
    copy_to_if_dqblk(&idq, &fdq);
    if (copy_to_user(addr, &idq, sizeof(idq)))
        return -EFAULT;
    return 0;
}

static void copy_from_if_dqblk(struct fs_disk_quota *dst, struct if_dqblk *src)
{
    dst->d_blk_hardlimit = src->dqb_bhardlimit;
    dst->d_blk_softlimit  = src->dqb_bsoftlimit;
    dst->d_bcount = src->dqb_curspace;
    dst->d_ino_hardlimit = src->dqb_ihardlimit;
    dst->d_ino_softlimit = src->dqb_isoftlimit;
    dst->d_icount = src->dqb_curinodes;
    dst->d_btimer = src->dqb_btime;
    dst->d_itimer = src->dqb_itime;

    dst->d_fieldmask = 0;
    if (src->dqb_valid & QIF_BLIMITS)
        dst->d_fieldmask |= FS_DQ_BSOFT | FS_DQ_BHARD;
    if (src->dqb_valid & QIF_SPACE)
        dst->d_fieldmask |= FS_DQ_BCOUNT;
    if (src->dqb_valid & QIF_ILIMITS)
        dst->d_fieldmask |= FS_DQ_ISOFT | FS_DQ_IHARD;
    if (src->dqb_valid & QIF_INODES)
        dst->d_fieldmask |= FS_DQ_ICOUNT;
    if (src->dqb_valid & QIF_BTIME)
        dst->d_fieldmask |= FS_DQ_BTIMER;
    if (src->dqb_valid & QIF_ITIME)
        dst->d_fieldmask |= FS_DQ_ITIMER;
}

static int quota_setquota(struct super_block *sb, int type, qid_t id,
              void __user *addr)
{
    struct fs_disk_quota fdq;
    struct if_dqblk idq;
    struct kqid qid;

    if (copy_from_user(&idq, addr, sizeof(idq)))
        return -EFAULT;
    if (!sb->s_qcop->set_dqblk)
        return -ENOSYS;
    qid = make_kqid(current_user_ns(), type, id);
    if (!qid_valid(qid))
        return -EINVAL;
    copy_from_if_dqblk(&fdq, &idq);
    return sb->s_qcop->set_dqblk(sb, qid, &fdq);
}

static int quota_setxstate(struct super_block *sb, int cmd, void __user *addr)
{
    __u32 flags;

    if (copy_from_user(&flags, addr, sizeof(flags)))
        return -EFAULT;
    if (!sb->s_qcop->set_xstate)
        return -ENOSYS;
    return sb->s_qcop->set_xstate(sb, flags, cmd);
}

static int quota_getxstate(struct super_block *sb, void __user *addr)
{
    struct fs_quota_stat fqs;
    int ret;

    if (!sb->s_qcop->get_xstate)
        return -ENOSYS;
    ret = sb->s_qcop->get_xstate(sb, &fqs);
    if (!ret && copy_to_user(addr, &fqs, sizeof(fqs)))
        return -EFAULT;
    return ret;
}

static int quota_setxquota(struct super_block *sb, int type, qid_t id,
               void __user *addr)
{
    struct fs_disk_quota fdq;
    struct kqid qid;

    if (copy_from_user(&fdq, addr, sizeof(fdq)))
        return -EFAULT;
    if (!sb->s_qcop->set_dqblk)
        return -ENOSYS;
    qid = make_kqid(current_user_ns(), type, id);
    if (!qid_valid(qid))
        return -EINVAL;
    return sb->s_qcop->set_dqblk(sb, qid, &fdq);
}

static int quota_getxquota(struct super_block *sb, int type, qid_t id,
               void __user *addr)
{
    struct fs_disk_quota fdq;
    struct kqid qid;
    int ret;

    if (!sb->s_qcop->get_dqblk)
        return -ENOSYS;
    qid = make_kqid(current_user_ns(), type, id);
    if (!qid_valid(qid))
        return -EINVAL;
    ret = sb->s_qcop->get_dqblk(sb, qid, &fdq);
    if (!ret && copy_to_user(addr, &fdq, sizeof(fdq)))
        return -EFAULT;
    return ret;
}

/* Copy parameters and call proper function */
static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id,
               void __user *addr, struct path *path)
{
    int ret;

    if (type >= (XQM_COMMAND(cmd) ? XQM_MAXQUOTAS : MAXQUOTAS))
        return -EINVAL;
    if (!sb->s_qcop)
        return -ENOSYS;

    ret = check_quotactl_permission(sb, type, cmd, id);
    if (ret < 0)
        return ret;

    switch (cmd) {
    case Q_QUOTAON:
        return quota_quotaon(sb, type, cmd, id, path);
    case Q_QUOTAOFF:
        if (!sb->s_qcop->quota_off)
            return -ENOSYS;
        return sb->s_qcop->quota_off(sb, type);
    case Q_GETFMT:
        return quota_getfmt(sb, type, addr);
    case Q_GETINFO:
        return quota_getinfo(sb, type, addr);
    case Q_SETINFO:
        return quota_setinfo(sb, type, addr);
    case Q_GETQUOTA:
        return quota_getquota(sb, type, id, addr);
    case Q_SETQUOTA:
        return quota_setquota(sb, type, id, addr);
    case Q_SYNC:
        if (!sb->s_qcop->quota_sync)
            return -ENOSYS;
        return sb->s_qcop->quota_sync(sb, type);
    case Q_XQUOTAON:
    case Q_XQUOTAOFF:
    case Q_XQUOTARM:
        return quota_setxstate(sb, cmd, addr);
    case Q_XGETQSTAT:
        return quota_getxstate(sb, addr);
    case Q_XSETQLIM:
        return quota_setxquota(sb, type, id, addr);
    case Q_XGETQUOTA:
        return quota_getxquota(sb, type, id, addr);
    case Q_XQUOTASYNC:
        if (sb->s_flags & MS_RDONLY)
            return -EROFS;
        /* XFS quotas are fully coherent now, making this call a noop */
        return 0;
    default:
        return -EINVAL;
    }
}

/* Return 1 if 'cmd' will block on frozen filesystem */
static int quotactl_cmd_write(int cmd)
{
    switch (cmd) {
    case Q_GETFMT:
    case Q_GETINFO:
    case Q_SYNC:
    case Q_XGETQSTAT:
    case Q_XGETQUOTA:
    case Q_XQUOTASYNC:
        return 0;
    }
    return 1;
}

/*
 * look up a superblock on which quota ops will be performed
 * - use the name of a block device to find the superblock thereon
 */
static struct super_block *quotactl_block(const char __user *special, int cmd)
{
#ifdef CONFIG_BLOCK
    struct block_device *bdev;
    struct super_block *sb;
    struct filename *tmp = getname(special);

    if (IS_ERR(tmp))
        return ERR_CAST(tmp);
    bdev = lookup_bdev(tmp->name);
    putname(tmp);
    if (IS_ERR(bdev))
        return ERR_CAST(bdev);
    if (quotactl_cmd_write(cmd))
        sb = get_super_thawed(bdev);
    else
        sb = get_super(bdev);
    bdput(bdev);
    if (!sb)
        return ERR_PTR(-ENODEV);

    return sb;
#else
    return ERR_PTR(-ENODEV);
#endif
}

/*
 * This is the system call interface. This communicates with
 * the user-level programs. Currently this only supports diskquota
 * calls. Maybe we need to add the process quotas etc. in the future,
 * but we probably should use rlimits for that.
 */
SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
        qid_t, id, void __user *, addr)
{
    uint cmds, type;
    struct super_block *sb = NULL;
    struct path path, *pathp = NULL;
    int ret;

    cmds = cmd >> SUBCMDSHIFT;
    type = cmd & SUBCMDMASK;

    /*
     * As a special case Q_SYNC can be called without a specific device.
     * It will iterate all superblocks that have quota enabled and call
     * the sync action on each of them.
     */
    if (!special) {
        if (cmds == Q_SYNC)
            return quota_sync_all(type);
        return -ENODEV;
    }

    /*
     * Path for quotaon has to be resolved before grabbing superblock
     * because that gets s_umount sem which is also possibly needed by path
     * resolution (think about autofs) and thus deadlocks could arise.
     */
    if (cmds == Q_QUOTAON) {
        ret = user_path_at(AT_FDCWD, addr, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
        if (ret)
            pathp = ERR_PTR(ret);
        else
            pathp = &path;
    }

    sb = quotactl_block(special, cmds);
    if (IS_ERR(sb)) {
        ret = PTR_ERR(sb);
        goto out;
    }

    ret = do_quotactl(sb, type, cmds, id, addr, pathp);

    drop_super(sb);
out:
    if (pathp && !IS_ERR(pathp))
        path_put(pathp);
    return ret;
}