// SPDX-License-Identifier: GPL-2.0-only

#include "dev.h"
#include "fuse_i.h"

static int fuse_fill_creds(struct fuse_mount *fm, struct fuse_args *args, struct mnt_idmap *idmap)
{
        struct fuse_conn *fc = fm->fc;
        bool no_idmap = !fm->sb || (fm->sb->s_iflags & SB_I_NOIDMAP);
        kuid_t fsuid = mapped_fsuid(idmap, fc->user_ns);
        kgid_t fsgid = mapped_fsgid(idmap, fc->user_ns);

        args->pid = pid_nr_ns(task_pid(current), fc->pid_ns);

        if (args->force) {
                if (args->nocreds)
                        return 0;

                if (no_idmap) {
                        args->uid = from_kuid_munged(fc->user_ns, current_fsuid());
                        args->gid = from_kgid_munged(fc->user_ns, current_fsgid());
                } else {
                        args->uid = FUSE_INVALID_UIDGID;
                        args->gid = FUSE_INVALID_UIDGID;
                }
                return 0;
        }

        WARN_ON(args->nocreds);
        /*
         * Keep the old behavior when idmappings support was not
         * declared by a FUSE server.
         *
         * For those FUSE servers who support idmapped mounts, we send UID/GID
         * only along with "inode creation" fuse requests, otherwise idmap ==
         * &invalid_mnt_idmap and req->in.h.{u,g}id will be equal to
         * FUSE_INVALID_UIDGID.
         */
        if (no_idmap) {
                fsuid = current_fsuid();
                fsgid = current_fsgid();
        }
        args->uid = from_kuid(fc->user_ns, fsuid);
        args->gid = from_kgid(fc->user_ns, fsgid);

        if (no_idmap && unlikely(args->uid == ((uid_t)-1) || args->gid == ((gid_t)-1)))
                return -EOVERFLOW;

        return 0;
}

static int fuse_req_prep(struct fuse_mount *fm, struct fuse_args *args, struct mnt_idmap *idmap)
{
        if (!args->force && fm->fc->conn_error)
                return -ECONNREFUSED;

        return fuse_fill_creds(fm, args, idmap);
}

ssize_t __fuse_simple_request(struct mnt_idmap *idmap, struct fuse_mount *fm,
                              struct fuse_args *args)
{
        struct fuse_conn *fc = fm->fc;
        int err = fuse_req_prep(fm, args, idmap);

        if (err)
                return err;

        return fuse_chan_send(fc->chan, args);
}

int fuse_simple_background(struct fuse_mount *fm, struct fuse_args *args, gfp_t gfp_flags)
{
        struct fuse_conn *fc = fm->fc;
        int err;

        WARN_ON(args->force && !args->nocreds);

        err = fuse_req_prep(fm, args, &invalid_mnt_idmap);
        if (err)
                return err;

        return fuse_chan_send_bg(fc->chan, args, gfp_flags);
}
EXPORT_SYMBOL_GPL(fuse_simple_background);

int fuse_simple_notify_reply(struct fuse_mount *fm, struct fuse_args *args, u64 unique)
{
        struct fuse_conn *fc = fm->fc;
        int err;

        WARN_ON(args->force && !args->nocreds);

        err = fuse_req_prep(fm, args, &invalid_mnt_idmap);
        if (err)
                return err;

        return fuse_chan_send_notify_reply(fc->chan, args, unique);
}