Commit d42eb23b authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: don't require /dev/fuse fd to be kept open during mount 



With the new mount API the sequence of syscalls would be:

        fs_fd = fsopen("fuse", 0);
	snprintf(opt, sizeof(opt), "%i", devfd);
	fsconfig(fs_fd, FSCONFIG_SET_STRING, "fd", opt, 0);
	/* ... */
	fsconfig(fs_fd, FSCONFIG_CMD_CREATE, 0, 0, 0);

Current mount code just stores the value of devfd in the fs_context and
uses it in during FSCONFIG_CMD_CREATE, which is inelegant.

Instead grab a reference to the underlying fuse_dev, and use that during
the filesystem creation.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent e9bf3850

fs/fuse/fuse_i.h

+1 −3
Original line number Diff line number Diff line
@@ -606,13 +606,11 @@ static inline bool fuse_is_inode_dax_mode(enum fuse_dax_mode mode) 
}



struct fuse_fs_context {

	int fd;

	struct file *file;

	struct fuse_dev *fud;

	unsigned int rootmode;

	kuid_t user_id;

	kgid_t group_id;

	bool is_bdev:1;

	bool fd_present:1;

	bool rootmode_present:1;

	bool user_id_present:1;

	bool group_id_present:1;

fs/fuse/inode.c

+33 −24
Original line number Diff line number Diff line
@@ -803,6 +803,29 @@ static const struct fs_parameter_spec fuse_fs_parameters[] = { 
	{}

};



static int fuse_opt_fd(struct fs_context *fsc, int fd)

{

	struct fuse_fs_context *ctx = fsc->fs_private;

	struct file *file __free(fput) = fget(fd);



	if (!file)

		return -EBADF;



	if (file->f_op != &fuse_dev_operations)

		return invalfc(fsc, "fd is not a fuse device");

	/*

	 * Require mount to happen from the same user namespace which

	 * opened /dev/fuse to prevent potential attacks.

	 */

	if (file->f_cred->user_ns != fsc->user_ns)

		return invalfc(fsc, "wrong user namespace for fuse device");



	ctx->fud = file->private_data;

	refcount_inc(&ctx->fud->ref);



	return 0;

}



static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param)

{

	struct fs_parse_result result;
@@ -842,9 +865,7 @@ static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param) 
		return 0;



	case OPT_FD:

		ctx->fd = result.uint_32;

		ctx->fd_present = true;

		break;

		return fuse_opt_fd(fsc, result.uint_32);



	case OPT_ROOTMODE:

		if (!fuse_valid_type(result.uint_32))
@@ -907,6 +928,8 @@ static void fuse_free_fsc(struct fs_context *fsc) 
	struct fuse_fs_context *ctx = fsc->fs_private;



	if (ctx) {

		if (ctx->fud)

			fuse_dev_put(ctx->fud);

		kfree(ctx->subtype);

		kfree(ctx);

	}
@@ -1849,7 +1872,7 @@ EXPORT_SYMBOL_GPL(fuse_init_fs_context_submount); 


int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)

{

	struct fuse_dev *fud = ctx->file ? fuse_file_to_fud(ctx->file) : NULL;

	struct fuse_dev *fud = ctx->fud;

	struct fuse_mount *fm = get_fuse_mount_super(sb);

	struct fuse_conn *fc = fm->fc;

	struct inode *root;
@@ -1950,18 +1973,10 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc) 
	struct fuse_mount *fm;

	int err;



	if (!ctx->file || !ctx->rootmode_present ||

	if (!ctx->fud || !ctx->rootmode_present ||

	    !ctx->user_id_present || !ctx->group_id_present)

		return -EINVAL;



	/*

	 * Require mount to happen from the same user namespace which

	 * opened /dev/fuse to prevent potential attacks.

	 */

	if ((ctx->file->f_op != &fuse_dev_operations) ||

	    (ctx->file->f_cred->user_ns != sb->s_user_ns))

		return -EINVAL;



	err = fuse_fill_super_common(sb, ctx);

	if (err)

		return err;
@@ -1982,14 +1997,14 @@ static int fuse_set_no_super(struct super_block *sb, struct fs_context *fsc) 


static int fuse_test_super(struct super_block *sb, struct fs_context *fsc)

{

	struct fuse_dev *fud = fsc->sget_key;



	return fsc->sget_key == get_fuse_conn_super(sb);

	return fuse_dev_fc_get(fud) == get_fuse_conn_super(sb);

}



static int fuse_get_tree(struct fs_context *fsc)

{

	struct fuse_fs_context *ctx = fsc->fs_private;

	struct fuse_dev *fud;

	struct fuse_conn *fc;

	struct fuse_mount *fm;

	struct super_block *sb;
@@ -2010,9 +2025,6 @@ static int fuse_get_tree(struct fs_context *fsc) 


	fsc->s_fs_info = fm;



	if (ctx->fd_present)

		ctx->file = fget(ctx->fd);



	if (IS_ENABLED(CONFIG_BLOCK) && ctx->is_bdev) {

		err = get_tree_bdev(fsc, fuse_fill_super);

		goto out;
@@ -2022,16 +2034,15 @@ static int fuse_get_tree(struct fs_context *fsc) 
	 * (found by device name), normal fuse mounts can't

	 */

	err = -EINVAL;

	if (!ctx->file)

	if (!ctx->fud)

		goto out;



	/*

	 * Allow creating a fuse mount with an already initialized fuse

	 * connection

	 */

	fud = __fuse_get_dev(ctx->file);

	if (ctx->file->f_op == &fuse_dev_operations && fud) {

		fsc->sget_key = fud->fc;

	if (fuse_dev_fc_get(ctx->fud)) {

		fsc->sget_key = ctx->fud;

		sb = sget_fc(fsc, fuse_test_super, fuse_set_no_super);

		err = PTR_ERR_OR_ZERO(sb);

		if (!IS_ERR(sb))
@@ -2042,8 +2053,6 @@ static int fuse_get_tree(struct fs_context *fsc) 
out:

	if (fsc->s_fs_info)

		fuse_mount_destroy(fm);

	if (ctx->file)

		fput(ctx->file);

	return err;

}