Re: [PATCH RESEND v2 15/18] fuse: Add support for pid namespaces

[Miklos Szeredi]

On Mon, Jan 04, 2016 at 12:03:54PM -0600, Seth Forshee wrote:
> If the userspace process servicing fuse requests is running in
> a pid namespace then pids passed via the fuse fd need to be
> translated relative to that namespace. Capture the pid namespace
> in use when the filesystem is mounted and use this for pid
> translation.
> 
> Since no use case currently exists for changing namespaces all
> translations are done relative to the pid namespace in use when
> /dev/fuse is opened.

The above doesn't match what the patch does.

 - FUSE captures namespace at mount time

 - CUSE captures namespace at /dev/cuse open


>  Mounting or /dev/fuse IO from another
> namespace will return errors.
> 
> Requests from processes whose pid cannot be translated into the
> target namespace are not permitted, except for requests
> allocated via fuse_get_req_nofail_nopages. For no-fail requests
> in.h.pid will be 0 if the pid translation fails.
> 
> File locking changes based on previous work done by Eric
> Biederman.
> 
> Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>

Not sure how my SOB got on this patch, use this instead:

Acked-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>

> ---
>  fs/fuse/dev.c    | 19 +++++++++++++++----
>  fs/fuse/file.c   | 22 +++++++++++++++++-----
>  fs/fuse/fuse_i.h |  4 ++++
>  fs/fuse/inode.c  |  3 +++
>  4 files changed, 39 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index ebb5e37455a0..a4f6f30d6d86 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -19,6 +19,7 @@
>  #include <linux/pipe_fs_i.h>
>  #include <linux/swap.h>
>  #include <linux/splice.h>
> +#include <linux/sched.h>
>  
>  MODULE_ALIAS_MISCDEV(FUSE_MINOR);
>  MODULE_ALIAS("devname:fuse");
> @@ -124,11 +125,11 @@ static void __fuse_put_request(struct fuse_req *req)
>  	atomic_dec(&req->count);
>  }
>  
> -static void fuse_req_init_context(struct fuse_req *req)
> +static void fuse_req_init_context(struct fuse_conn *fc, struct fuse_req *req)
>  {
>  	req->in.h.uid = from_kuid_munged(&init_user_ns, current_fsuid());
>  	req->in.h.gid = from_kgid_munged(&init_user_ns, current_fsgid());
> -	req->in.h.pid = current->pid;
> +	req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
>  }
>  
>  void fuse_set_initialized(struct fuse_conn *fc)
> @@ -181,10 +182,14 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
>  		goto out;
>  	}
>  
> -	fuse_req_init_context(req);
> +	fuse_req_init_context(fc, req);
>  	__set_bit(FR_WAITING, &req->flags);
>  	if (for_background)
>  		__set_bit(FR_BACKGROUND, &req->flags);
> +	if (req->in.h.pid == 0) {
> +		fuse_put_request(fc, req);
> +		return ERR_PTR(-EOVERFLOW);
> +	}
>  
>  	return req;
>  
> @@ -274,7 +279,7 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
>  	if (!req)
>  		req = get_reserved_req(fc, file);
>  
> -	fuse_req_init_context(req);
> +	fuse_req_init_context(fc, req);
>  	__set_bit(FR_WAITING, &req->flags);
>  	__clear_bit(FR_BACKGROUND, &req->flags);
>  	return req;
> @@ -1243,6 +1248,9 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
>  	struct fuse_in *in;
>  	unsigned reqsize;
>  
> +	if (task_active_pid_ns(current) != fc->pid_ns)
> +		return -EIO;
> +
>   restart:
>  	spin_lock(&fiq->waitq.lock);
>  	err = -EAGAIN;
> @@ -1872,6 +1880,9 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
>  	struct fuse_req *req;
>  	struct fuse_out_header oh;
>  
> +	if (task_active_pid_ns(current) != fc->pid_ns)
> +		return -EIO;
> +
>  	if (nbytes < sizeof(struct fuse_out_header))
>  		return -EINVAL;
>  
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index e0faf8f2c868..a6c7484c94ee 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2061,7 +2061,8 @@ static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
>  	return generic_file_mmap(file, vma);
>  }
>  
> -static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
> +static int convert_fuse_file_lock(struct fuse_conn *fc,
> +				  const struct fuse_file_lock *ffl,
>  				  struct file_lock *fl)
>  {
>  	switch (ffl->type) {
> @@ -2076,7 +2077,14 @@ static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
>  
>  		fl->fl_start = ffl->start;
>  		fl->fl_end = ffl->end;
> -		fl->fl_pid = ffl->pid;
> +
> +		/*
> +		 * Convert pid into the caller's pid namespace. If the pid
> +		 * does not map into the namespace fl_pid will get set to 0.
> +		 */
> +		rcu_read_lock();
> +		fl->fl_pid = pid_vnr(find_pid_ns(ffl->pid, fc->pid_ns));
> +		rcu_read_unlock();
>  		break;
>  
>  	default:
> @@ -2125,7 +2133,7 @@ static int fuse_getlk(struct file *file, struct file_lock *fl)
>  	args.out.args[0].value = &outarg;
>  	err = fuse_simple_request(fc, &args);
>  	if (!err)
> -		err = convert_fuse_file_lock(&outarg.lk, fl);
> +		err = convert_fuse_file_lock(fc, &outarg.lk, fl);
>  
>  	return err;
>  }
> @@ -2137,7 +2145,8 @@ static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
>  	FUSE_ARGS(args);
>  	struct fuse_lk_in inarg;
>  	int opcode = (fl->fl_flags & FL_SLEEP) ? FUSE_SETLKW : FUSE_SETLK;
> -	pid_t pid = fl->fl_type != F_UNLCK ? current->tgid : 0;
> +	struct pid *pid = fl->fl_type != F_UNLCK ? task_tgid(current) : NULL;
> +	pid_t pid_nr = pid_nr_ns(pid, fc->pid_ns);
>  	int err;
>  
>  	if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
> @@ -2149,7 +2158,10 @@ static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
>  	if (fl->fl_flags & FL_CLOSE)
>  		return 0;
>  
> -	fuse_lk_fill(&args, file, fl, opcode, pid, flock, &inarg);
> +	if (pid && pid_nr == 0)
> +		return -EOVERFLOW;
> +
> +	fuse_lk_fill(&args, file, fl, opcode, pid_nr, flock, &inarg);
>  	err = fuse_simple_request(fc, &args);
>  
>  	/* locking is restartable */
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 405113101db8..143b595197b6 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -22,6 +22,7 @@
>  #include <linux/rbtree.h>
>  #include <linux/poll.h>
>  #include <linux/workqueue.h>
> +#include <linux/pid_namespace.h>
>  
>  /** Max number of pages that can be used in a single read request */
>  #define FUSE_MAX_PAGES_PER_REQ 32
> @@ -456,6 +457,9 @@ struct fuse_conn {
>  	/** The group id for this mount */
>  	kgid_t group_id;
>  
> +	/** The pid namespace for this mount */
> +	struct pid_namespace *pid_ns;
> +
>  	/** The fuse mount flags for this mount */
>  	unsigned flags;
>  
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 2913db2a5b99..2f31874ea9db 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -20,6 +20,7 @@
>  #include <linux/random.h>
>  #include <linux/sched.h>
>  #include <linux/exportfs.h>
> +#include <linux/pid_namespace.h>
>  
>  MODULE_AUTHOR("Miklos Szeredi <miklos@xxxxxxxxxx>");
>  MODULE_DESCRIPTION("Filesystem in Userspace");
> @@ -609,6 +610,7 @@ void fuse_conn_init(struct fuse_conn *fc)
>  	fc->connected = 1;
>  	fc->attr_version = 1;
>  	get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
> +	fc->pid_ns = get_pid_ns(task_active_pid_ns(current));
>  }
>  EXPORT_SYMBOL_GPL(fuse_conn_init);
>  
> @@ -617,6 +619,7 @@ void fuse_conn_put(struct fuse_conn *fc)
>  	if (atomic_dec_and_test(&fc->count)) {
>  		if (fc->destroy_req)
>  			fuse_request_free(fc->destroy_req);
> +		put_pid_ns(fc->pid_ns);
>  		fc->release(fc);
>  	}
>  }
> -- 
> 1.9.1
>