Re: [PATCH] sunrpc: make debugfs file creation failure non-fatal

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Mar 30, 2015 at 07:47:53PM -0400, J. Bruce Fields wrote:
> ACK.--b.

But note the result after this is that the debugfs directories will
always miss gss-proxy clients on selinux-enforcing systems.  That could
be really confusing.

So we should still fix debugfs's permission checking.  It doesn't make
sense to me as is.

--b.

> 
> On Mon, Mar 30, 2015 at 05:58:18PM -0400, Jeff Layton wrote:
> > We currently have a problem that SELinux policy is being enforced when
> > creating debugfs files. If a debugfs file is created as a side effect of
> > doing some syscall, then that creation can fail if the SELinux policy
> > for that process prevents it.
> > 
> > This seems wrong. We don't do that for files under /proc, for instance,
> > so Bruce has proposed a patch to fix that.
> > 
> > While discussing that patch however, Greg K.H. stated:
> > 
> >     "No kernel code should care / fail if a debugfs function fails, so
> >      please fix up the sunrpc code first."
> > 
> > This patch converts all of the sunrpc debugfs setup code to be void
> > return functins, and the callers to not look for errors from those
> > functions.
> > 
> > This should allow rpc_clnt and rpc_xprt creation to work, even if the
> > kernel fails to create debugfs files for some reason.
> > 
> > Cc: "J. Bruce Fields" <bfields@fieldses.org>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
> > ---
> >  include/linux/sunrpc/debug.h | 18 +++++++++---------
> >  net/sunrpc/clnt.c            |  4 +---
> >  net/sunrpc/debugfs.c         | 34 +++++++++++++---------------------
> >  net/sunrpc/sunrpc_syms.c     |  7 +------
> >  net/sunrpc/xprt.c            |  7 +------
> >  5 files changed, 25 insertions(+), 45 deletions(-)
> > 
> > diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
> > index c57d8ea0716c..59a7889e15db 100644
> > --- a/include/linux/sunrpc/debug.h
> > +++ b/include/linux/sunrpc/debug.h
> > @@ -60,17 +60,17 @@ struct rpc_xprt;
> >  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
> >  void		rpc_register_sysctl(void);
> >  void		rpc_unregister_sysctl(void);
> > -int		sunrpc_debugfs_init(void);
> > +void		sunrpc_debugfs_init(void);
> >  void		sunrpc_debugfs_exit(void);
> > -int		rpc_clnt_debugfs_register(struct rpc_clnt *);
> > +void		rpc_clnt_debugfs_register(struct rpc_clnt *);
> >  void		rpc_clnt_debugfs_unregister(struct rpc_clnt *);
> > -int		rpc_xprt_debugfs_register(struct rpc_xprt *);
> > +void		rpc_xprt_debugfs_register(struct rpc_xprt *);
> >  void		rpc_xprt_debugfs_unregister(struct rpc_xprt *);
> >  #else
> > -static inline int
> > +static inline void
> >  sunrpc_debugfs_init(void)
> >  {
> > -	return 0;
> > +	return;
> >  }
> >  
> >  static inline void
> > @@ -79,10 +79,10 @@ sunrpc_debugfs_exit(void)
> >  	return;
> >  }
> >  
> > -static inline int
> > +static inline void
> >  rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
> >  {
> > -	return 0;
> > +	return;
> >  }
> >  
> >  static inline void
> > @@ -91,10 +91,10 @@ rpc_clnt_debugfs_unregister(struct rpc_clnt *clnt)
> >  	return;
> >  }
> >  
> > -static inline int
> > +static inline void
> >  rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
> >  {
> > -	return 0;
> > +	return;
> >  }
> >  
> >  static inline void
> > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> > index 612aa73bbc60..e6ce1517367f 100644
> > --- a/net/sunrpc/clnt.c
> > +++ b/net/sunrpc/clnt.c
> > @@ -303,9 +303,7 @@ static int rpc_client_register(struct rpc_clnt *clnt,
> >  	struct super_block *pipefs_sb;
> >  	int err;
> >  
> > -	err = rpc_clnt_debugfs_register(clnt);
> > -	if (err)
> > -		return err;
> > +	rpc_clnt_debugfs_register(clnt);
> >  
> >  	pipefs_sb = rpc_get_sb_net(net);
> >  	if (pipefs_sb) {
> > diff --git a/net/sunrpc/debugfs.c b/net/sunrpc/debugfs.c
> > index e811f390f9f6..1c2e3960b939 100644
> > --- a/net/sunrpc/debugfs.c
> > +++ b/net/sunrpc/debugfs.c
> > @@ -129,32 +129,30 @@ static const struct file_operations tasks_fops = {
> >  	.release	= tasks_release,
> >  };
> >  
> > -int
> > +void
> >  rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
> >  {
> > -	int len, err;
> > +	int len;
> >  	char name[24]; /* enough for "../../rpc_xprt/ + 8 hex digits + NULL */
> >  
> >  	/* Already registered? */
> >  	if (clnt->cl_debugfs)
> > -		return 0;
> > +		return;
> >  
> >  	len = snprintf(name, sizeof(name), "%x", clnt->cl_clid);
> >  	if (len >= sizeof(name))
> > -		return -EINVAL;
> > +		return;
> >  
> >  	/* make the per-client dir */
> >  	clnt->cl_debugfs = debugfs_create_dir(name, rpc_clnt_dir);
> >  	if (!clnt->cl_debugfs)
> > -		return -ENOMEM;
> > +		return;
> >  
> >  	/* make tasks file */
> > -	err = -ENOMEM;
> >  	if (!debugfs_create_file("tasks", S_IFREG | S_IRUSR, clnt->cl_debugfs,
> >  				 clnt, &tasks_fops))
> >  		goto out_err;
> >  
> > -	err = -EINVAL;
> >  	rcu_read_lock();
> >  	len = snprintf(name, sizeof(name), "../../rpc_xprt/%s",
> >  			rcu_dereference(clnt->cl_xprt)->debugfs->d_name.name);
> > @@ -162,15 +160,13 @@ rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
> >  	if (len >= sizeof(name))
> >  		goto out_err;
> >  
> > -	err = -ENOMEM;
> >  	if (!debugfs_create_symlink("xprt", clnt->cl_debugfs, name))
> >  		goto out_err;
> >  
> > -	return 0;
> > +	return;
> >  out_err:
> >  	debugfs_remove_recursive(clnt->cl_debugfs);
> >  	clnt->cl_debugfs = NULL;
> > -	return err;
> >  }
> >  
> >  void
> > @@ -226,7 +222,7 @@ static const struct file_operations xprt_info_fops = {
> >  	.release	= xprt_info_release,
> >  };
> >  
> > -int
> > +void
> >  rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
> >  {
> >  	int len, id;
> > @@ -237,22 +233,19 @@ rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
> >  
> >  	len = snprintf(name, sizeof(name), "%x", id);
> >  	if (len >= sizeof(name))
> > -		return -EINVAL;
> > +		return;
> >  
> >  	/* make the per-client dir */
> >  	xprt->debugfs = debugfs_create_dir(name, rpc_xprt_dir);
> >  	if (!xprt->debugfs)
> > -		return -ENOMEM;
> > +		return;
> >  
> >  	/* make tasks file */
> >  	if (!debugfs_create_file("info", S_IFREG | S_IRUSR, xprt->debugfs,
> >  				 xprt, &xprt_info_fops)) {
> >  		debugfs_remove_recursive(xprt->debugfs);
> >  		xprt->debugfs = NULL;
> > -		return -ENOMEM;
> >  	}
> > -
> > -	return 0;
> >  }
> >  
> >  void
> > @@ -266,14 +259,15 @@ void __exit
> >  sunrpc_debugfs_exit(void)
> >  {
> >  	debugfs_remove_recursive(topdir);
> > +	topdir = NULL;
> >  }
> >  
> > -int __init
> > +void __init
> >  sunrpc_debugfs_init(void)
> >  {
> >  	topdir = debugfs_create_dir("sunrpc", NULL);
> >  	if (!topdir)
> > -		goto out;
> > +		return;
> >  
> >  	rpc_clnt_dir = debugfs_create_dir("rpc_clnt", topdir);
> >  	if (!rpc_clnt_dir)
> > @@ -283,10 +277,8 @@ sunrpc_debugfs_init(void)
> >  	if (!rpc_xprt_dir)
> >  		goto out_remove;
> >  
> > -	return 0;
> > +	return;
> >  out_remove:
> >  	debugfs_remove_recursive(topdir);
> >  	topdir = NULL;
> > -out:
> > -	return -ENOMEM;
> >  }
> > diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
> > index e37fbed87956..ee5d3d253102 100644
> > --- a/net/sunrpc/sunrpc_syms.c
> > +++ b/net/sunrpc/sunrpc_syms.c
> > @@ -98,10 +98,7 @@ init_sunrpc(void)
> >  	if (err)
> >  		goto out4;
> >  
> > -	err = sunrpc_debugfs_init();
> > -	if (err)
> > -		goto out5;
> > -
> > +	sunrpc_debugfs_init();
> >  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
> >  	rpc_register_sysctl();
> >  #endif
> > @@ -109,8 +106,6 @@ init_sunrpc(void)
> >  	init_socket_xprt();	/* clnt sock transport */
> >  	return 0;
> >  
> > -out5:
> > -	unregister_rpc_pipefs();
> >  out4:
> >  	unregister_pernet_subsys(&sunrpc_net_ops);
> >  out3:
> > diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> > index e3015aede0d9..9949722d99ce 100644
> > --- a/net/sunrpc/xprt.c
> > +++ b/net/sunrpc/xprt.c
> > @@ -1331,7 +1331,6 @@ static void xprt_init(struct rpc_xprt *xprt, struct net *net)
> >   */
> >  struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
> >  {
> > -	int err;
> >  	struct rpc_xprt	*xprt;
> >  	struct xprt_class *t;
> >  
> > @@ -1372,11 +1371,7 @@ found:
> >  		return ERR_PTR(-ENOMEM);
> >  	}
> >  
> > -	err = rpc_xprt_debugfs_register(xprt);
> > -	if (err) {
> > -		xprt_destroy(xprt);
> > -		return ERR_PTR(err);
> > -	}
> > +	rpc_xprt_debugfs_register(xprt);
> >  
> >  	dprintk("RPC:       created transport %p with %u slots\n", xprt,
> >  			xprt->max_reqs);
> > -- 
> > 2.1.0