Re: [PATCH] nfsd: check passed socket's net matches NFSd superblock's one

[J. Bruce Fields]

On Tue, Feb 18, 2014 at 07:19:31PM +0400, Stanislav Kinsbursky wrote:
> 18.02.2014 02:19, J. Bruce Fields ÐÐÑÐÑ:
> >On Sat, Feb 15, 2014 at 09:51:20AM +0800, Weng Meiling wrote:
> >>Hi Bruce,
> >>
> >>The upstream has merged your git tree for-3.14, but there is no this patch?
> >>Do you forget this patch?
> >
> >Apologies, I'm not sure what happened.
> >
> >Looking back at it....  The patch causes all my pynfs reboot recovery
> >tests to fail.  They're just doing a "systemctl restart
> >nfs-server.service", and "systemctl status nfs-server.service" shows in
> >part
> >
> >	ExecStart=/usr/sbin/rpc.nfsd $RPCNFSDARGS $RPCNFSDCOUNT (code=exited, status=1/FAILURE)
> >
> >So the patch is causing rpc.nfsd to fail?  No network namespaces should
> >be involved.
> >
> >I haven't investigated any further.
> >
> 
> Hi Bruce,
> Are you sure, that exactly this patch broke your pynfs tests?
> BTW, systemd manipulates namespaces. Maybe the patch revealed some pynfs internal bugs?
> What do you think?

It's really just "systemctl restart nfs-server.service" that the patch
breaks, pynfs isn't involved much.

The patch I'm actually using follows, but I believe the only difference
is in the printk message?

--b

commit e1f2922c12cb59baba0f2c7726bee992a0861310
Author: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Date:   Mon Dec 30 17:23:59 2013 +0300

    nfsd: check passed socket's net matches the NFSd superblock's
    
    The file descriptor written to the nfsd/portlist file could be for a
    socket in a different network namespace from the network namespace that
    the nfsd filesystem was mounted in, and this can cause a crash.
    
    For example: "ip netns exec" creates a new network and mount namespace,
    which duplicates the nfsd mount point which was created in the init_net
    context.  Thus NFS server stop in the nested network context leads to
    RPCBIND client destruction in init_net.  Then, on nfsd start in the
    nested network context, the rpc.nfsd process creates a socket in the
    nested net and passes it into "write_ports", which leads to RPCBIND
    socket creation in init_net context for the same reason (the nfsd mount
    point was created in the init_net context). An attempt to register
    passed socket in nested net leads to panic, because no RPCBIND client is
    present in the nested network namespace.
    
    This patch adds a check that the passed the socket's net matches the
    nfsd superblock's net, and returns -EINVAL error to user space if not.
    
    Reported-by: Weng Meiling <wengmeiling.weng@xxxxxxxxxx>
    Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 7f55517..1331766 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -699,6 +699,11 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net)
 	if (err != 0 || fd < 0)
 		return -EINVAL;
 
+	if (svc_alien_sock(net, fd)) {
+		printk(KERN_ERR "%s: socket net is different from NFSd's\n", __func__);
+		return -EINVAL;
+	}
+
 	err = nfsd_create_serv(net);
 	if (err != 0)
 		return err;
diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index 62fd1b7..947009e 100644
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -56,6 +56,7 @@ int		svc_recv(struct svc_rqst *, long);
 int		svc_send(struct svc_rqst *);
 void		svc_drop(struct svc_rqst *);
 void		svc_sock_update_bufs(struct svc_serv *serv);
+bool		svc_alien_sock(struct net *net, int fd);
 int		svc_addsock(struct svc_serv *serv, const int fd,
 					char *name_return, const size_t len);
 void		svc_init_xprt_sock(void);
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index b6e59f0..3ba5b87 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1397,6 +1397,17 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
 	return svsk;
 }
 
+bool svc_alien_sock(struct net *net, int fd)
+{
+	int err;
+	struct socket *sock = sockfd_lookup(fd, &err);
+
+	if (sock && (sock_net(sock->sk) != net))
+		return true;
+	return false;
+}
+EXPORT_SYMBOL_GPL(svc_alien_sock);
+
 /**
  * svc_addsock - add a listener socket to an RPC service
  * @serv: pointer to RPC service to which to add a new listener
--
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