fs: Add VirtualBox guest shared folder (vboxsf) support
VirtualBox hosts can share folders with guests, this commit adds a
VFS driver implementing the Linux-guest side of this, allowing folders
exported by the host to be mounted under Linux.
This driver depends on the guest <-> host IPC functions exported by
the vboxguest driver.
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/vboxsf/super.c b/fs/vboxsf/super.c
new file mode 100644
index 0000000..675e2698
--- /dev/null
+++ b/fs/vboxsf/super.c
@@ -0,0 +1,491 @@
+// SPDX-License-Identifier: MIT
+/*
+ * VirtualBox Guest Shared Folders support: Virtual File System.
+ *
+ * Module initialization/finalization
+ * File system registration/deregistration
+ * Superblock reading
+ * Few utility functions
+ *
+ * Copyright (C) 2006-2018 Oracle Corporation
+ */
+
+#include <linux/idr.h>
+#include <linux/fs_parser.h>
+#include <linux/magic.h>
+#include <linux/module.h>
+#include <linux/nls.h>
+#include <linux/statfs.h>
+#include <linux/vbox_utils.h>
+#include "vfsmod.h"
+
+#define VBOXSF_SUPER_MAGIC 0x786f4256 /* 'VBox' little endian */
+
+#define VBSF_MOUNT_SIGNATURE_BYTE_0 ('\000')
+#define VBSF_MOUNT_SIGNATURE_BYTE_1 ('\377')
+#define VBSF_MOUNT_SIGNATURE_BYTE_2 ('\376')
+#define VBSF_MOUNT_SIGNATURE_BYTE_3 ('\375')
+
+static int follow_symlinks;
+module_param(follow_symlinks, int, 0444);
+MODULE_PARM_DESC(follow_symlinks,
+ "Let host resolve symlinks rather than showing them");
+
+static DEFINE_IDA(vboxsf_bdi_ida);
+static DEFINE_MUTEX(vboxsf_setup_mutex);
+static bool vboxsf_setup_done;
+static struct super_operations vboxsf_super_ops; /* forward declaration */
+static struct kmem_cache *vboxsf_inode_cachep;
+
+static char * const vboxsf_default_nls = CONFIG_NLS_DEFAULT;
+
+enum { opt_nls, opt_uid, opt_gid, opt_ttl, opt_dmode, opt_fmode,
+ opt_dmask, opt_fmask };
+
+static const struct fs_parameter_spec vboxsf_fs_parameters[] = {
+ fsparam_string ("nls", opt_nls),
+ fsparam_u32 ("uid", opt_uid),
+ fsparam_u32 ("gid", opt_gid),
+ fsparam_u32 ("ttl", opt_ttl),
+ fsparam_u32oct ("dmode", opt_dmode),
+ fsparam_u32oct ("fmode", opt_fmode),
+ fsparam_u32oct ("dmask", opt_dmask),
+ fsparam_u32oct ("fmask", opt_fmask),
+ {}
+};
+
+static int vboxsf_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+ struct vboxsf_fs_context *ctx = fc->fs_private;
+ struct fs_parse_result result;
+ kuid_t uid;
+ kgid_t gid;
+ int opt;
+
+ opt = fs_parse(fc, vboxsf_fs_parameters, param, &result);
+ if (opt < 0)
+ return opt;
+
+ switch (opt) {
+ case opt_nls:
+ if (ctx->nls_name || fc->purpose != FS_CONTEXT_FOR_MOUNT) {
+ vbg_err("vboxsf: Cannot reconfigure nls option\n");
+ return -EINVAL;
+ }
+ ctx->nls_name = param->string;
+ param->string = NULL;
+ break;
+ case opt_uid:
+ uid = make_kuid(current_user_ns(), result.uint_32);
+ if (!uid_valid(uid))
+ return -EINVAL;
+ ctx->o.uid = uid;
+ break;
+ case opt_gid:
+ gid = make_kgid(current_user_ns(), result.uint_32);
+ if (!gid_valid(gid))
+ return -EINVAL;
+ ctx->o.gid = gid;
+ break;
+ case opt_ttl:
+ ctx->o.ttl = msecs_to_jiffies(result.uint_32);
+ break;
+ case opt_dmode:
+ if (result.uint_32 & ~0777)
+ return -EINVAL;
+ ctx->o.dmode = result.uint_32;
+ ctx->o.dmode_set = true;
+ break;
+ case opt_fmode:
+ if (result.uint_32 & ~0777)
+ return -EINVAL;
+ ctx->o.fmode = result.uint_32;
+ ctx->o.fmode_set = true;
+ break;
+ case opt_dmask:
+ if (result.uint_32 & ~07777)
+ return -EINVAL;
+ ctx->o.dmask = result.uint_32;
+ break;
+ case opt_fmask:
+ if (result.uint_32 & ~07777)
+ return -EINVAL;
+ ctx->o.fmask = result.uint_32;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+ struct vboxsf_fs_context *ctx = fc->fs_private;
+ struct shfl_string *folder_name, root_path;
+ struct vboxsf_sbi *sbi;
+ struct dentry *droot;
+ struct inode *iroot;
+ char *nls_name;
+ size_t size;
+ int err;
+
+ if (!fc->source)
+ return -EINVAL;
+
+ sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
+ if (!sbi)
+ return -ENOMEM;
+
+ sbi->o = ctx->o;
+ idr_init(&sbi->ino_idr);
+ spin_lock_init(&sbi->ino_idr_lock);
+ sbi->next_generation = 1;
+ sbi->bdi_id = -1;
+
+ /* Load nls if not utf8 */
+ nls_name = ctx->nls_name ? ctx->nls_name : vboxsf_default_nls;
+ if (strcmp(nls_name, "utf8") != 0) {
+ if (nls_name == vboxsf_default_nls)
+ sbi->nls = load_nls_default();
+ else
+ sbi->nls = load_nls(nls_name);
+
+ if (!sbi->nls) {
+ vbg_err("vboxsf: Count not load '%s' nls\n", nls_name);
+ err = -EINVAL;
+ goto fail_free;
+ }
+ }
+
+ sbi->bdi_id = ida_simple_get(&vboxsf_bdi_ida, 0, 0, GFP_KERNEL);
+ if (sbi->bdi_id < 0) {
+ err = sbi->bdi_id;
+ goto fail_free;
+ }
+
+ err = super_setup_bdi_name(sb, "vboxsf-%s.%d", fc->source, sbi->bdi_id);
+ if (err)
+ goto fail_free;
+
+ /* Turn source into a shfl_string and map the folder */
+ size = strlen(fc->source) + 1;
+ folder_name = kmalloc(SHFLSTRING_HEADER_SIZE + size, GFP_KERNEL);
+ if (!folder_name) {
+ err = -ENOMEM;
+ goto fail_free;
+ }
+ folder_name->size = size;
+ folder_name->length = size - 1;
+ strlcpy(folder_name->string.utf8, fc->source, size);
+ err = vboxsf_map_folder(folder_name, &sbi->root);
+ kfree(folder_name);
+ if (err) {
+ vbg_err("vboxsf: Host rejected mount of '%s' with error %d\n",
+ fc->source, err);
+ goto fail_free;
+ }
+
+ root_path.length = 1;
+ root_path.size = 2;
+ root_path.string.utf8[0] = '/';
+ root_path.string.utf8[1] = 0;
+ err = vboxsf_stat(sbi, &root_path, &sbi->root_info);
+ if (err)
+ goto fail_unmap;
+
+ sb->s_magic = VBOXSF_SUPER_MAGIC;
+ sb->s_blocksize = 1024;
+ sb->s_maxbytes = MAX_LFS_FILESIZE;
+ sb->s_op = &vboxsf_super_ops;
+ sb->s_d_op = &vboxsf_dentry_ops;
+
+ iroot = iget_locked(sb, 0);
+ if (!iroot) {
+ err = -ENOMEM;
+ goto fail_unmap;
+ }
+ vboxsf_init_inode(sbi, iroot, &sbi->root_info);
+ unlock_new_inode(iroot);
+
+ droot = d_make_root(iroot);
+ if (!droot) {
+ err = -ENOMEM;
+ goto fail_unmap;
+ }
+
+ sb->s_root = droot;
+ sb->s_fs_info = sbi;
+ return 0;
+
+fail_unmap:
+ vboxsf_unmap_folder(sbi->root);
+fail_free:
+ if (sbi->bdi_id >= 0)
+ ida_simple_remove(&vboxsf_bdi_ida, sbi->bdi_id);
+ if (sbi->nls)
+ unload_nls(sbi->nls);
+ idr_destroy(&sbi->ino_idr);
+ kfree(sbi);
+ return err;
+}
+
+static void vboxsf_inode_init_once(void *data)
+{
+ struct vboxsf_inode *sf_i = data;
+
+ mutex_init(&sf_i->handle_list_mutex);
+ inode_init_once(&sf_i->vfs_inode);
+}
+
+static struct inode *vboxsf_alloc_inode(struct super_block *sb)
+{
+ struct vboxsf_inode *sf_i;
+
+ sf_i = kmem_cache_alloc(vboxsf_inode_cachep, GFP_NOFS);
+ if (!sf_i)
+ return NULL;
+
+ sf_i->force_restat = 0;
+ INIT_LIST_HEAD(&sf_i->handle_list);
+
+ return &sf_i->vfs_inode;
+}
+
+static void vboxsf_free_inode(struct inode *inode)
+{
+ struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
+ unsigned long flags;
+
+ spin_lock_irqsave(&sbi->ino_idr_lock, flags);
+ idr_remove(&sbi->ino_idr, inode->i_ino);
+ spin_unlock_irqrestore(&sbi->ino_idr_lock, flags);
+ kmem_cache_free(vboxsf_inode_cachep, VBOXSF_I(inode));
+}
+
+static void vboxsf_put_super(struct super_block *sb)
+{
+ struct vboxsf_sbi *sbi = VBOXSF_SBI(sb);
+
+ vboxsf_unmap_folder(sbi->root);
+ if (sbi->bdi_id >= 0)
+ ida_simple_remove(&vboxsf_bdi_ida, sbi->bdi_id);
+ if (sbi->nls)
+ unload_nls(sbi->nls);
+
+ /*
+ * vboxsf_free_inode uses the idr, make sure all delayed rcu free
+ * inodes are flushed.
+ */
+ rcu_barrier();
+ idr_destroy(&sbi->ino_idr);
+ kfree(sbi);
+}
+
+static int vboxsf_statfs(struct dentry *dentry, struct kstatfs *stat)
+{
+ struct super_block *sb = dentry->d_sb;
+ struct shfl_volinfo shfl_volinfo;
+ struct vboxsf_sbi *sbi;
+ u32 buf_len;
+ int err;
+
+ sbi = VBOXSF_SBI(sb);
+ buf_len = sizeof(shfl_volinfo);
+ err = vboxsf_fsinfo(sbi->root, 0, SHFL_INFO_GET | SHFL_INFO_VOLUME,
+ &buf_len, &shfl_volinfo);
+ if (err)
+ return err;
+
+ stat->f_type = VBOXSF_SUPER_MAGIC;
+ stat->f_bsize = shfl_volinfo.bytes_per_allocation_unit;
+
+ do_div(shfl_volinfo.total_allocation_bytes,
+ shfl_volinfo.bytes_per_allocation_unit);
+ stat->f_blocks = shfl_volinfo.total_allocation_bytes;
+
+ do_div(shfl_volinfo.available_allocation_bytes,
+ shfl_volinfo.bytes_per_allocation_unit);
+ stat->f_bfree = shfl_volinfo.available_allocation_bytes;
+ stat->f_bavail = shfl_volinfo.available_allocation_bytes;
+
+ stat->f_files = 1000;
+ /*
+ * Don't return 0 here since the guest may then think that it is not
+ * possible to create any more files.
+ */
+ stat->f_ffree = 1000000;
+ stat->f_fsid.val[0] = 0;
+ stat->f_fsid.val[1] = 0;
+ stat->f_namelen = 255;
+ return 0;
+}
+
+static struct super_operations vboxsf_super_ops = {
+ .alloc_inode = vboxsf_alloc_inode,
+ .free_inode = vboxsf_free_inode,
+ .put_super = vboxsf_put_super,
+ .statfs = vboxsf_statfs,
+};
+
+static int vboxsf_setup(void)
+{
+ int err;
+
+ mutex_lock(&vboxsf_setup_mutex);
+
+ if (vboxsf_setup_done)
+ goto success;
+
+ vboxsf_inode_cachep =
+ kmem_cache_create("vboxsf_inode_cache",
+ sizeof(struct vboxsf_inode), 0,
+ (SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
+ SLAB_ACCOUNT),
+ vboxsf_inode_init_once);
+ if (!vboxsf_inode_cachep) {
+ err = -ENOMEM;
+ goto fail_nomem;
+ }
+
+ err = vboxsf_connect();
+ if (err) {
+ vbg_err("vboxsf: err %d connecting to guest PCI-device\n", err);
+ vbg_err("vboxsf: make sure you are inside a VirtualBox VM\n");
+ vbg_err("vboxsf: and check dmesg for vboxguest errors\n");
+ goto fail_free_cache;
+ }
+
+ err = vboxsf_set_utf8();
+ if (err) {
+ vbg_err("vboxsf_setutf8 error %d\n", err);
+ goto fail_disconnect;
+ }
+
+ if (!follow_symlinks) {
+ err = vboxsf_set_symlinks();
+ if (err)
+ vbg_warn("vboxsf: Unable to show symlinks: %d\n", err);
+ }
+
+ vboxsf_setup_done = true;
+success:
+ mutex_unlock(&vboxsf_setup_mutex);
+ return 0;
+
+fail_disconnect:
+ vboxsf_disconnect();
+fail_free_cache:
+ kmem_cache_destroy(vboxsf_inode_cachep);
+fail_nomem:
+ mutex_unlock(&vboxsf_setup_mutex);
+ return err;
+}
+
+static int vboxsf_parse_monolithic(struct fs_context *fc, void *data)
+{
+ char *options = data;
+
+ if (options && options[0] == VBSF_MOUNT_SIGNATURE_BYTE_0 &&
+ options[1] == VBSF_MOUNT_SIGNATURE_BYTE_1 &&
+ options[2] == VBSF_MOUNT_SIGNATURE_BYTE_2 &&
+ options[3] == VBSF_MOUNT_SIGNATURE_BYTE_3) {
+ vbg_err("vboxsf: Old binary mount data not supported, remove obsolete mount.vboxsf and/or update your VBoxService.\n");
+ return -EINVAL;
+ }
+
+ return generic_parse_monolithic(fc, data);
+}
+
+static int vboxsf_get_tree(struct fs_context *fc)
+{
+ int err;
+
+ err = vboxsf_setup();
+ if (err)
+ return err;
+
+ return get_tree_nodev(fc, vboxsf_fill_super);
+}
+
+static int vboxsf_reconfigure(struct fs_context *fc)
+{
+ struct vboxsf_sbi *sbi = VBOXSF_SBI(fc->root->d_sb);
+ struct vboxsf_fs_context *ctx = fc->fs_private;
+ struct inode *iroot = fc->root->d_sb->s_root->d_inode;
+
+ /* Apply changed options to the root inode */
+ sbi->o = ctx->o;
+ vboxsf_init_inode(sbi, iroot, &sbi->root_info);
+
+ return 0;
+}
+
+static void vboxsf_free_fc(struct fs_context *fc)
+{
+ struct vboxsf_fs_context *ctx = fc->fs_private;
+
+ kfree(ctx->nls_name);
+ kfree(ctx);
+}
+
+static const struct fs_context_operations vboxsf_context_ops = {
+ .free = vboxsf_free_fc,
+ .parse_param = vboxsf_parse_param,
+ .parse_monolithic = vboxsf_parse_monolithic,
+ .get_tree = vboxsf_get_tree,
+ .reconfigure = vboxsf_reconfigure,
+};
+
+static int vboxsf_init_fs_context(struct fs_context *fc)
+{
+ struct vboxsf_fs_context *ctx;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ current_uid_gid(&ctx->o.uid, &ctx->o.gid);
+
+ fc->fs_private = ctx;
+ fc->ops = &vboxsf_context_ops;
+ return 0;
+}
+
+static struct file_system_type vboxsf_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "vboxsf",
+ .init_fs_context = vboxsf_init_fs_context,
+ .kill_sb = kill_anon_super
+};
+
+/* Module initialization/finalization handlers */
+static int __init vboxsf_init(void)
+{
+ return register_filesystem(&vboxsf_fs_type);
+}
+
+static void __exit vboxsf_fini(void)
+{
+ unregister_filesystem(&vboxsf_fs_type);
+
+ mutex_lock(&vboxsf_setup_mutex);
+ if (vboxsf_setup_done) {
+ vboxsf_disconnect();
+ /*
+ * Make sure all delayed rcu free inodes are flushed
+ * before we destroy the cache.
+ */
+ rcu_barrier();
+ kmem_cache_destroy(vboxsf_inode_cachep);
+ }
+ mutex_unlock(&vboxsf_setup_mutex);
+}
+
+module_init(vboxsf_init);
+module_exit(vboxsf_fini);
+
+MODULE_DESCRIPTION("Oracle VM VirtualBox Module for Host File System Access");
+MODULE_AUTHOR("Oracle Corporation");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_FS("vboxsf");
