[PATCH v3 4/4] fuse: define the filesystem as untrusted

[Mimi Zohar]

Hi Miklos,

On Tue, 2018-03-13 at 14:32 -0500, Eric W. Biederman wrote:
> Mimi Zohar <zohar at linux.vnet.ibm.com> writes:
> 
> > Files on FUSE can change at any point in time without IMA being able
> > to detect it.  The file data read for the file signature verification
> > could be totally different from what is subsequently read, making the
> > signature verification useless.
> >
> > FUSE can be mounted by unprivileged users either today with fusermount
> > installed with setuid, or soon with the upcoming patches to allow FUSE
> > mounts in a non-init user namespace.
> >
> > This patch sets the SB_I_IMA_UNVERIFIABLE_SIGNATURE flag and when
> > appropriate sets the SB_I_UNTRUSTED_MOUNTER flag.
> 
> Acked-by: "Eric W. Biederman" <ebiederm at xmission.com>

There's been a number of changes since the original version of this
patch set.  I would appreciate your Ack for this version?

Thanks,

Mimi


> >
> > Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
> > Cc: Miklos Szeredi <miklos at szeredi.hu>
> > Cc: Seth Forshee <seth.forshee at canonical.com>
> > Cc: Eric W. Biederman <ebiederm at xmission.com>
> > Cc: Dongsu Park <dongsu at kinvolk.io>
> > Cc: Alban Crequy <alban at kinvolk.io>
> > Cc: "Serge E. Hallyn" <serge at hallyn.com>
> > ---
> >  fs/fuse/inode.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> > index 624f18bbfd2b..ef309958e060 100644
> > --- a/fs/fuse/inode.c
> > +++ b/fs/fuse/inode.c
> > @@ -1080,6 +1080,9 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
> >  	sb->s_maxbytes = MAX_LFS_FILESIZE;
> >  	sb->s_time_gran = 1;
> >  	sb->s_export_op = &fuse_export_operations;
> > +	sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
> > +	if (sb->s_user_ns != &init_user_ns)
> > +		sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
> >  
> >  	file = fget(d.fd);
> >  	err = -EINVAL;
> 

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