// SPDX-License-Identifier: GPL-2.0/* * FUSE passthrough to backing file. * * Copyright (c) 2023 CTERA Networks. */ #include "dev.h"#include "fuse_i.h" #include <linux/file.h> struct fuse_backing *fuse_backing_get(struct fuse_backing *fb){	if (fb && refcount_inc_not_zero(&fb->count))		return fb;	return NULL;} static void fuse_backing_free(struct fuse_backing *fb){	pr_debug("%s: fb=0x%p\n", __func__, fb); 	if (fb->file)		fput(fb->file);	put_cred(fb->cred);	kfree_rcu(fb, rcu);} void fuse_backing_put(struct fuse_backing *fb){	if (fb && refcount_dec_and_test(&fb->count))		fuse_backing_free(fb);} void fuse_backing_files_init(struct fuse_conn *fc){	idr_init(&fc->backing_files_map);} static int fuse_backing_id_alloc(struct fuse_conn *fc, struct fuse_backing *fb){	int id; 	idr_preload(GFP_KERNEL);	spin_lock(&fc->lock);	/* FIXME: xarray might be space inefficient */	id = idr_alloc_cyclic(&fc->backing_files_map, fb, 1, 0, GFP_ATOMIC);	spin_unlock(&fc->lock);	idr_preload_end(); 	WARN_ON_ONCE(id == 0);	return id;} static struct fuse_backing *fuse_backing_id_remove(struct fuse_conn *fc,						   int id){	struct fuse_backing *fb; 	spin_lock(&fc->lock);	fb = idr_remove(&fc->backing_files_map, id);	spin_unlock(&fc->lock); 	return fb;} static int fuse_backing_id_free(int id, void *p, void *data){	struct fuse_backing *fb = p; 	WARN_ON_ONCE(refcount_read(&fb->count) != 1);	fuse_backing_free(fb);	return 0;} void fuse_backing_files_free(struct fuse_conn *fc){	idr_for_each(&fc->backing_files_map, fuse_backing_id_free, NULL);	idr_destroy(&fc->backing_files_map);} int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map){	struct file *file;	struct super_block *backing_sb;	struct fuse_backing *fb = NULL;	int res; 	pr_debug("%s: fd=%d flags=0x%x\n", __func__, map->fd, map->flags); 	/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */	res = -EPERM;	if (!fc->passthrough || !capable(CAP_SYS_ADMIN))		goto out; 	res = -EINVAL;	if (map->flags || map->padding)		goto out; 	file = fget_raw(map->fd);	res = -EBADF;	if (!file)		goto out; 	/* read/write/splice/mmap passthrough only relevant for regular files */	res = d_is_dir(file->f_path.dentry) ? -EISDIR : -EINVAL;	if (!d_is_reg(file->f_path.dentry))		goto out_fput; 	backing_sb = file_inode(file)->i_sb;	res = -ELOOP;	if (backing_sb->s_stack_depth >= fc->max_stack_depth)		goto out_fput; 	fb = kmalloc_obj(struct fuse_backing);	res = -ENOMEM;	if (!fb)		goto out_fput; 	fb->file = file;	fb->cred = get_current_cred();	refcount_set(&fb->count, 1); 	res = fuse_backing_id_alloc(fc, fb);	if (res < 0) {		fuse_backing_free(fb);		fb = NULL;	} out:	pr_debug("%s: fb=0x%p, ret=%i\n", __func__, fb, res); 	return res; out_fput:	fput(file);	goto out;} int fuse_backing_close(struct fuse_conn *fc, int backing_id){	struct fuse_backing *fb = NULL;	int err; 	pr_debug("%s: backing_id=%d\n", __func__, backing_id); 	/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */	err = -EPERM;	if (!fc->passthrough || !capable(CAP_SYS_ADMIN))		goto out; 	err = -EINVAL;	if (backing_id <= 0)		goto out; 	err = -ENOENT;	fb = fuse_backing_id_remove(fc, backing_id);	if (!fb)		goto out; 	fuse_backing_put(fb);	err = 0;out:	pr_debug("%s: fb=0x%p, err=%i\n", __func__, fb, err); 	return err;} struct fuse_backing *fuse_backing_lookup(struct fuse_conn *fc, int backing_id){	struct fuse_backing *fb; 	rcu_read_lock();	fb = idr_find(&fc->backing_files_map, backing_id);	fb = fuse_backing_get(fb);	rcu_read_unlock(); 	return fb;}