Commit dfb84c33 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: allow synchronous FUSE_INIT 



FUSE_INIT has always been asynchronous with mount.  That means that the
server processed this request after the mount syscall returned.

This means that FUSE_INIT can't supply the root inode's ID, hence it
currently has a hardcoded value.  There are other limitations such as not
being able to perform getxattr during mount, which is needed by selinux.

To remove these limitations allow server to process FUSE_INIT while
initializing the in-core super block for the fuse filesystem.  This can
only be done if the server is prepared to handle this, so add
FUSE_DEV_IOC_SYNC_INIT ioctl, which

 a) lets the server know whether this feature is supported, returning
 ENOTTY othewrwise.

 b) lets the kernel know to perform a synchronous initialization

The implementation is slightly tricky, since fuse_dev/fuse_conn are set up
only during super block creation.  This is solved by setting the private
data of the fuse device file to a special value ((struct fuse_dev *) 1) and
waiting for this to be turned into a proper fuse_dev before commecing with
operations on the device file.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 3ca1b311

fs/fuse/cuse.c

+2 −1
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
#include <linux/user_namespace.h>



#include "fuse_i.h"

#include "fuse_dev_i.h"



#define CUSE_CONNTBL_LEN	64
@@ -547,7 +548,7 @@ static int cuse_channel_open(struct inode *inode, struct file *file) 
 */

static int cuse_channel_release(struct inode *inode, struct file *file)

{

	struct fuse_dev *fud = file->private_data;

	struct fuse_dev *fud = __fuse_get_dev(file);

	struct cuse_conn *cc = fc_to_cc(fud->fc);



	/* remove from the conntbl, no more access from this point on */

fs/fuse/dev.c

+53 −18
Original line number Diff line number Diff line
@@ -1530,14 +1530,34 @@ static int fuse_dev_open(struct inode *inode, struct file *file) 
	return 0;

}



struct fuse_dev *fuse_get_dev(struct file *file)

{

	struct fuse_dev *fud = __fuse_get_dev(file);

	int err;



	if (likely(fud))

		return fud;



	err = wait_event_interruptible(fuse_dev_waitq,

				       READ_ONCE(file->private_data) != FUSE_DEV_SYNC_INIT);

	if (err)

		return ERR_PTR(err);



	fud = __fuse_get_dev(file);

	if (!fud)

		return ERR_PTR(-EPERM);



	return fud;

}



static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)

{

	struct fuse_copy_state cs;

	struct file *file = iocb->ki_filp;

	struct fuse_dev *fud = fuse_get_dev(file);



	if (!fud)

		return -EPERM;

	if (IS_ERR(fud))

		return PTR_ERR(fud);



	if (!user_backed_iter(to))

		return -EINVAL;
@@ -1557,8 +1577,8 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos, 
	struct fuse_copy_state cs;

	struct fuse_dev *fud = fuse_get_dev(in);



	if (!fud)

		return -EPERM;

	if (IS_ERR(fud))

		return PTR_ERR(fud);



	bufs = kvmalloc_array(pipe->max_usage, sizeof(struct pipe_buffer),

			      GFP_KERNEL);
@@ -2231,7 +2251,7 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud, 
static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)

{

	struct fuse_copy_state cs;

	struct fuse_dev *fud = fuse_get_dev(iocb->ki_filp);

	struct fuse_dev *fud = __fuse_get_dev(iocb->ki_filp);



	if (!fud)

		return -EPERM;
@@ -2253,11 +2273,10 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe, 
	unsigned idx;

	struct pipe_buffer *bufs;

	struct fuse_copy_state cs;

	struct fuse_dev *fud;

	struct fuse_dev *fud = __fuse_get_dev(out);

	size_t rem;

	ssize_t ret;



	fud = fuse_get_dev(out);

	if (!fud)

		return -EPERM;
@@ -2343,7 +2362,7 @@ static __poll_t fuse_dev_poll(struct file *file, poll_table *wait) 
	struct fuse_iqueue *fiq;

	struct fuse_dev *fud = fuse_get_dev(file);



	if (!fud)

	if (IS_ERR(fud))

		return EPOLLERR;



	fiq = &fud->fc->iq;
@@ -2490,7 +2509,7 @@ void fuse_wait_aborted(struct fuse_conn *fc) 


int fuse_dev_release(struct inode *inode, struct file *file)

{

	struct fuse_dev *fud = fuse_get_dev(file);

	struct fuse_dev *fud = __fuse_get_dev(file);



	if (fud) {

		struct fuse_conn *fc = fud->fc;
@@ -2521,8 +2540,8 @@ static int fuse_dev_fasync(int fd, struct file *file, int on) 
{

	struct fuse_dev *fud = fuse_get_dev(file);



	if (!fud)

		return -EPERM;

	if (IS_ERR(fud))

		return PTR_ERR(fud);



	/* No locking - fasync_helper does its own locking */

	return fasync_helper(fd, file, on, &fud->fc->iq.fasync);
@@ -2532,7 +2551,7 @@ static int fuse_device_clone(struct fuse_conn *fc, struct file *new) 
{

	struct fuse_dev *fud;



	if (new->private_data)

	if (__fuse_get_dev(new))

		return -EINVAL;



	fud = fuse_dev_alloc_install(fc);
@@ -2563,7 +2582,7 @@ static long fuse_dev_ioctl_clone(struct file *file, __u32 __user *argp) 
	 * uses the same ioctl handler.

	 */

	if (fd_file(f)->f_op == file->f_op)

		fud = fuse_get_dev(fd_file(f));

		fud = __fuse_get_dev(fd_file(f));



	res = -EINVAL;

	if (fud) {
@@ -2581,8 +2600,8 @@ static long fuse_dev_ioctl_backing_open(struct file *file, 
	struct fuse_dev *fud = fuse_get_dev(file);

	struct fuse_backing_map map;



	if (!fud)

		return -EPERM;

	if (IS_ERR(fud))

		return PTR_ERR(fud);



	if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))

		return -EOPNOTSUPP;
@@ -2598,8 +2617,8 @@ static long fuse_dev_ioctl_backing_close(struct file *file, __u32 __user *argp) 
	struct fuse_dev *fud = fuse_get_dev(file);

	int backing_id;



	if (!fud)

		return -EPERM;

	if (IS_ERR(fud))

		return PTR_ERR(fud);



	if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))

		return -EOPNOTSUPP;
@@ -2610,6 +2629,19 @@ static long fuse_dev_ioctl_backing_close(struct file *file, __u32 __user *argp) 
	return fuse_backing_close(fud->fc, backing_id);

}



static long fuse_dev_ioctl_sync_init(struct file *file)

{

	int err = -EINVAL;



	mutex_lock(&fuse_mutex);

	if (!__fuse_get_dev(file)) {

		WRITE_ONCE(file->private_data, FUSE_DEV_SYNC_INIT);

		err = 0;

	}

	mutex_unlock(&fuse_mutex);

	return err;

}



static long fuse_dev_ioctl(struct file *file, unsigned int cmd,

			   unsigned long arg)

{
@@ -2625,6 +2657,9 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd, 
	case FUSE_DEV_IOC_BACKING_CLOSE:

		return fuse_dev_ioctl_backing_close(file, argp);



	case FUSE_DEV_IOC_SYNC_INIT:

		return fuse_dev_ioctl_sync_init(file);



	default:

		return -ENOTTY;

	}
@@ -2633,7 +2668,7 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd, 
#ifdef CONFIG_PROC_FS

static void fuse_dev_show_fdinfo(struct seq_file *seq, struct file *file)

{

	struct fuse_dev *fud = fuse_get_dev(file);

	struct fuse_dev *fud = __fuse_get_dev(file);

	if (!fud)

		return;

fs/fuse/dev_uring.c

+2 −2
Original line number Diff line number Diff line
@@ -1139,9 +1139,9 @@ int fuse_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags) 
		return -EINVAL;



	fud = fuse_get_dev(cmd->file);

	if (!fud) {

	if (IS_ERR(fud)) {

		pr_info_ratelimited("No fuse device found\n");

		return -ENOTCONN;

		return PTR_ERR(fud);

	}

	fc = fud->fc;

fs/fuse/fuse_dev_i.h

+11 −2
Original line number Diff line number Diff line
@@ -12,6 +12,8 @@ 
#define FUSE_INT_REQ_BIT (1ULL << 0)

#define FUSE_REQ_ID_STEP (1ULL << 1)



extern struct wait_queue_head fuse_dev_waitq;



struct fuse_arg;

struct fuse_args;

struct fuse_pqueue;
@@ -37,15 +39,22 @@ struct fuse_copy_state { 
	} ring;

};



static inline struct fuse_dev *fuse_get_dev(struct file *file)

#define FUSE_DEV_SYNC_INIT ((struct fuse_dev *) 1)

#define FUSE_DEV_PTR_MASK (~1UL)



static inline struct fuse_dev *__fuse_get_dev(struct file *file)

{

	/*

	 * Lockless access is OK, because file->private data is set

	 * once during mount and is valid until the file is released.

	 */

	return READ_ONCE(file->private_data);

	struct fuse_dev *fud = READ_ONCE(file->private_data);



	return (typeof(fud)) ((unsigned long) fud & FUSE_DEV_PTR_MASK);

}



struct fuse_dev *fuse_get_dev(struct file *file);



unsigned int fuse_req_hash(u64 unique);

struct fuse_req *fuse_request_find(struct fuse_pqueue *fpq, u64 unique);

fs/fuse/fuse_i.h

+4 −1
Original line number Diff line number Diff line
@@ -904,6 +904,9 @@ struct fuse_conn { 
	/* Is link not implemented by fs? */

	unsigned int no_link:1;



	/* Is synchronous FUSE_INIT allowed? */

	unsigned int sync_init:1;



	/* Use io_uring for communication */

	unsigned int io_uring;
@@ -1318,7 +1321,7 @@ struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc); 
struct fuse_dev *fuse_dev_alloc(void);

void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc);

void fuse_dev_free(struct fuse_dev *fud);

void fuse_send_init(struct fuse_mount *fm);

int fuse_send_init(struct fuse_mount *fm);



/**

 * Fill in superblock and initialize fuse connection