[CRIU] [PATCH] mnt: relax constraints on fuse mounts

[Tycho Andersen]

On Thu, Apr 09, 2015 at 12:37:06PM +0300, Pavel Emelyanov wrote:
> On 04/08/2015 09:13 PM, Tycho Andersen wrote:
> > 1. If a fuse connection is present, but there are no fuse mounts of that type
> >    in the mount namespace, don't refuse to dump.
> > 2. If there are mounts of that type in the container but they are external,
> >    we're going to bind them anyway, so there's no fuse-specific things that
> >    need to be done, so it is safe to dump.
> > 
> > Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> > ---
> >  mount.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 42 insertions(+), 1 deletion(-)
> > 
> > diff --git a/mount.c b/mount.c
> > index 71c39bf..700c303 100644
> > --- a/mount.c
> > +++ b/mount.c
> > @@ -1024,6 +1024,47 @@ out:
> >  	return ret;
> >  }
> >  
> > +static int fusectl_dump(struct mount_info *pm)
> > +{
> > +	int fd, ret = -1;
> > +	struct dirent *de;
> > +	DIR *fdir = NULL;
> > +
> > +	fd = open_mountpoint(pm);
> > +	if (fd < 0)
> > +		return -1;
> > +
> > +	fdir = fdopendir(fd);
> > +	if (fdir == NULL) {
> > +		close(fd);
> > +		return -1;
> > +	}
> > +
> > +	while ((de = readdir(fdir))) {
> > +		int id;
> > +		struct mount_info *it;
> > +
> > +		if (dir_dots(de))
> > +			continue;
> > +
> > +		if (sscanf(de->d_name, "%d", &id) != 1) {
> > +			pr_err("wrong number of items scanned in fusectl dump\n");
> > +			goto out;
> > +		}
> > +
> > +		for (it = mntinfo; it; it = it->next) {
> > +			if (id == minor(it->s_dev) && !it->external) {
> 
> I'm not sure that minor number match is enough. Should we also check the
> it->type being fuse?

I think it should be safe in this case because we're excluding more
things than we should, rather than allowing stuff through. It is
better to compare against it->type, though, so I'll resend.

Tycho

> > +				pr_err("%s is a fuse mount but not external\n", it->mountpoint);
> > +				goto out;
> > +			}
> > +		}
> > +	}
> > +
> > +	ret = 0;
> > +out:
> > +	closedir(fdir);
> > +	return ret;
> > +}
> >  
> >  static int dump_empty_fs(struct mount_info *pm)
> >  {
> > @@ -1102,7 +1143,7 @@ static struct fstype fstypes[] = {
> >  		.code = FSTYPE__SECURITYFS,
> >  	}, {
> >  		.name = "fusectl",
> > -		.dump = dump_empty_fs,
> > +		.dump = fusectl_dump,
> >  		.code = FSTYPE__FUSECTL,
> >  	}, {
> >  		.name = "debugfs",
> > 
>