![Venkateswararao Jujjuri (JV)](/assets/img/avatar_default.png)
Recent zerocopy work in the 9P VirtIO transport maps and pins user buffers into kernel memory for the server to work on them. Since the user process can initiate this kind of pinning with a simple read/write call, thousands of IO threads initiated by the user process can hog the system resources and could result into denial of service. This patch introduces flow control to avoid that extreme scenario. The ceiling limit to avoid denial of service attacks is set to relatively high (nr_free_pagecache_pages()/4) so that it won't interfere with regular usage, but can step in extreme cases to limit the total system hang. Since we don't have a global structure to accommodate this variable, I choose the virtio_chan as the home for this. Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com> Reviewed-by: Badari Pulavarty <pbadari@us.ibm.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
616 lines
16 KiB
C
616 lines
16 KiB
C
/*
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* The Virtio 9p transport driver
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*
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* This is a block based transport driver based on the lguest block driver
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* code.
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*
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* Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
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*
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* Based on virtio console driver
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* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to:
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* Free Software Foundation
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02111-1301 USA
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*
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*/
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#include <linux/in.h>
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#include <linux/module.h>
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#include <linux/net.h>
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#include <linux/ipv6.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/un.h>
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#include <linux/uaccess.h>
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#include <linux/inet.h>
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#include <linux/idr.h>
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#include <linux/file.h>
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#include <linux/slab.h>
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#include <net/9p/9p.h>
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#include <linux/parser.h>
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#include <net/9p/client.h>
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#include <net/9p/transport.h>
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#include <linux/scatterlist.h>
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#include <linux/swap.h>
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#include <linux/virtio.h>
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#include <linux/virtio_9p.h>
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#include "trans_common.h"
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#define VIRTQUEUE_NUM 128
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/* a single mutex to manage channel initialization and attachment */
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static DEFINE_MUTEX(virtio_9p_lock);
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static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
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static atomic_t vp_pinned = ATOMIC_INIT(0);
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/**
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* struct virtio_chan - per-instance transport information
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* @initialized: whether the channel is initialized
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* @inuse: whether the channel is in use
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* @lock: protects multiple elements within this structure
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* @client: client instance
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* @vdev: virtio dev associated with this channel
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* @vq: virtio queue associated with this channel
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* @sg: scatter gather list which is used to pack a request (protected?)
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*
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* We keep all per-channel information in a structure.
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* This structure is allocated within the devices dev->mem space.
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* A pointer to the structure will get put in the transport private.
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*
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*/
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struct virtio_chan {
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bool inuse;
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spinlock_t lock;
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struct p9_client *client;
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struct virtio_device *vdev;
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struct virtqueue *vq;
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int ring_bufs_avail;
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wait_queue_head_t *vc_wq;
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/* This is global limit. Since we don't have a global structure,
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* will be placing it in each channel.
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*/
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int p9_max_pages;
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/* Scatterlist: can be too big for stack. */
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struct scatterlist sg[VIRTQUEUE_NUM];
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int tag_len;
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/*
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* tag name to identify a mount Non-null terminated
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*/
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char *tag;
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struct list_head chan_list;
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};
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static struct list_head virtio_chan_list;
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/* How many bytes left in this page. */
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static unsigned int rest_of_page(void *data)
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{
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return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
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}
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/**
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* p9_virtio_close - reclaim resources of a channel
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* @client: client instance
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*
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* This reclaims a channel by freeing its resources and
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* reseting its inuse flag.
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*
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*/
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static void p9_virtio_close(struct p9_client *client)
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{
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struct virtio_chan *chan = client->trans;
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mutex_lock(&virtio_9p_lock);
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if (chan)
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chan->inuse = false;
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mutex_unlock(&virtio_9p_lock);
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}
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/**
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* req_done - callback which signals activity from the server
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* @vq: virtio queue activity was received on
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*
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* This notifies us that the server has triggered some activity
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* on the virtio channel - most likely a response to request we
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* sent. Figure out which requests now have responses and wake up
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* those threads.
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*
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* Bugs: could do with some additional sanity checking, but appears to work.
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*
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*/
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static void req_done(struct virtqueue *vq)
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{
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struct virtio_chan *chan = vq->vdev->priv;
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struct p9_fcall *rc;
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unsigned int len;
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struct p9_req_t *req;
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unsigned long flags;
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P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
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while (1) {
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spin_lock_irqsave(&chan->lock, flags);
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rc = virtqueue_get_buf(chan->vq, &len);
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if (rc == NULL) {
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spin_unlock_irqrestore(&chan->lock, flags);
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break;
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}
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chan->ring_bufs_avail = 1;
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spin_unlock_irqrestore(&chan->lock, flags);
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/* Wakeup if anyone waiting for VirtIO ring space. */
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wake_up(chan->vc_wq);
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P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
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P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
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req = p9_tag_lookup(chan->client, rc->tag);
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if (req->tc->private) {
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struct trans_rpage_info *rp = req->tc->private;
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int p = rp->rp_nr_pages;
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/*Release pages */
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p9_release_req_pages(rp);
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atomic_sub(p, &vp_pinned);
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wake_up(&vp_wq);
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if (rp->rp_alloc)
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kfree(rp);
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req->tc->private = NULL;
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}
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req->status = REQ_STATUS_RCVD;
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p9_client_cb(chan->client, req);
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}
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}
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/**
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* pack_sg_list - pack a scatter gather list from a linear buffer
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* @sg: scatter/gather list to pack into
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* @start: which segment of the sg_list to start at
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* @limit: maximum segment to pack data to
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* @data: data to pack into scatter/gather list
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* @count: amount of data to pack into the scatter/gather list
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*
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* sg_lists have multiple segments of various sizes. This will pack
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* arbitrary data into an existing scatter gather list, segmenting the
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* data as necessary within constraints.
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*
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*/
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static int
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pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
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int count)
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{
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int s;
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int index = start;
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while (count) {
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s = rest_of_page(data);
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if (s > count)
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s = count;
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sg_set_buf(&sg[index++], data, s);
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count -= s;
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data += s;
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BUG_ON(index > limit);
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}
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return index-start;
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}
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/* We don't currently allow canceling of virtio requests */
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static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
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{
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return 1;
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}
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/**
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* pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer,
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* this takes a list of pages.
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* @sg: scatter/gather list to pack into
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* @start: which segment of the sg_list to start at
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* @pdata_off: Offset into the first page
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* @**pdata: a list of pages to add into sg.
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* @count: amount of data to pack into the scatter/gather list
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*/
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static int
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pack_sg_list_p(struct scatterlist *sg, int start, int limit, size_t pdata_off,
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struct page **pdata, int count)
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{
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int s;
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int i = 0;
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int index = start;
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if (pdata_off) {
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s = min((int)(PAGE_SIZE - pdata_off), count);
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sg_set_page(&sg[index++], pdata[i++], s, pdata_off);
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count -= s;
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}
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while (count) {
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BUG_ON(index > limit);
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s = min((int)PAGE_SIZE, count);
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sg_set_page(&sg[index++], pdata[i++], s, 0);
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count -= s;
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}
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return index-start;
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}
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/**
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* p9_virtio_request - issue a request
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* @client: client instance issuing the request
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* @req: request to be issued
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*
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*/
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static int
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p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
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{
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int in, out, inp, outp;
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struct virtio_chan *chan = client->trans;
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char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
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unsigned long flags;
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size_t pdata_off = 0;
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struct trans_rpage_info *rpinfo = NULL;
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int err, pdata_len = 0;
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
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req->status = REQ_STATUS_SENT;
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if (req->tc->pbuf_size && (req->tc->pubuf && P9_IS_USER_CONTEXT)) {
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int nr_pages = p9_nr_pages(req);
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int rpinfo_size = sizeof(struct trans_rpage_info) +
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sizeof(struct page *) * nr_pages;
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if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
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err = wait_event_interruptible(vp_wq,
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atomic_read(&vp_pinned) < chan->p9_max_pages);
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if (err == -ERESTARTSYS)
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return err;
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P9_DPRINTK(P9_DEBUG_TRANS, "9p: May gup pages now.\n");
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}
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if (rpinfo_size <= (req->tc->capacity - req->tc->size)) {
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/* We can use sdata */
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req->tc->private = req->tc->sdata + req->tc->size;
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rpinfo = (struct trans_rpage_info *)req->tc->private;
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rpinfo->rp_alloc = 0;
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} else {
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req->tc->private = kmalloc(rpinfo_size, GFP_NOFS);
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if (!req->tc->private) {
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: "
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"private kmalloc returned NULL");
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return -ENOMEM;
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}
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rpinfo = (struct trans_rpage_info *)req->tc->private;
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rpinfo->rp_alloc = 1;
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}
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err = p9_payload_gup(req, &pdata_off, &pdata_len, nr_pages,
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req->tc->id == P9_TREAD ? 1 : 0);
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if (err < 0) {
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if (rpinfo->rp_alloc)
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kfree(rpinfo);
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return err;
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} else {
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atomic_add(rpinfo->rp_nr_pages, &vp_pinned);
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}
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}
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req_retry_pinned:
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spin_lock_irqsave(&chan->lock, flags);
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/* Handle out VirtIO ring buffers */
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out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
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req->tc->size);
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if (req->tc->pbuf_size && (req->tc->id == P9_TWRITE)) {
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/* We have additional write payload buffer to take care */
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if (req->tc->pubuf && P9_IS_USER_CONTEXT) {
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outp = pack_sg_list_p(chan->sg, out, VIRTQUEUE_NUM,
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pdata_off, rpinfo->rp_data, pdata_len);
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} else {
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char *pbuf = req->tc->pubuf ? req->tc->pubuf :
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req->tc->pkbuf;
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outp = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM, pbuf,
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req->tc->pbuf_size);
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}
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out += outp;
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}
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/* Handle in VirtIO ring buffers */
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if (req->tc->pbuf_size &&
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((req->tc->id == P9_TREAD) || (req->tc->id == P9_TREADDIR))) {
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/*
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* Take care of additional Read payload.
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* 11 is the read/write header = PDU Header(7) + IO Size (4).
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* Arrange in such a way that server places header in the
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* alloced memory and payload onto the user buffer.
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*/
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inp = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM, rdata, 11);
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/*
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* Running executables in the filesystem may result in
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* a read request with kernel buffer as opposed to user buffer.
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*/
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if (req->tc->pubuf && P9_IS_USER_CONTEXT) {
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in = pack_sg_list_p(chan->sg, out+inp, VIRTQUEUE_NUM,
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pdata_off, rpinfo->rp_data, pdata_len);
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} else {
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char *pbuf = req->tc->pubuf ? req->tc->pubuf :
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req->tc->pkbuf;
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in = pack_sg_list(chan->sg, out+inp, VIRTQUEUE_NUM,
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pbuf, req->tc->pbuf_size);
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}
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in += inp;
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} else {
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in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM, rdata,
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client->msize);
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}
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err = virtqueue_add_buf(chan->vq, chan->sg, out, in, req->tc);
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if (err < 0) {
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if (err == -ENOSPC) {
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chan->ring_bufs_avail = 0;
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spin_unlock_irqrestore(&chan->lock, flags);
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err = wait_event_interruptible(*chan->vc_wq,
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chan->ring_bufs_avail);
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if (err == -ERESTARTSYS)
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return err;
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P9_DPRINTK(P9_DEBUG_TRANS, "9p:Retry virtio request\n");
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goto req_retry_pinned;
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} else {
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spin_unlock_irqrestore(&chan->lock, flags);
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P9_DPRINTK(P9_DEBUG_TRANS,
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"9p debug: "
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"virtio rpc add_buf returned failure");
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if (rpinfo && rpinfo->rp_alloc)
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kfree(rpinfo);
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return -EIO;
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}
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}
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virtqueue_kick(chan->vq);
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spin_unlock_irqrestore(&chan->lock, flags);
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
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return 0;
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}
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static ssize_t p9_mount_tag_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct virtio_chan *chan;
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struct virtio_device *vdev;
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vdev = dev_to_virtio(dev);
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chan = vdev->priv;
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return snprintf(buf, chan->tag_len + 1, "%s", chan->tag);
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}
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static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
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/**
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* p9_virtio_probe - probe for existence of 9P virtio channels
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* @vdev: virtio device to probe
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*
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* This probes for existing virtio channels.
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*
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*/
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static int p9_virtio_probe(struct virtio_device *vdev)
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{
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__u16 tag_len;
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char *tag;
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int err;
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struct virtio_chan *chan;
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chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
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if (!chan) {
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printk(KERN_ERR "9p: Failed to allocate virtio 9P channel\n");
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err = -ENOMEM;
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goto fail;
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}
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chan->vdev = vdev;
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/* We expect one virtqueue, for requests. */
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chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
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if (IS_ERR(chan->vq)) {
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err = PTR_ERR(chan->vq);
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goto out_free_vq;
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}
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chan->vq->vdev->priv = chan;
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spin_lock_init(&chan->lock);
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sg_init_table(chan->sg, VIRTQUEUE_NUM);
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chan->inuse = false;
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if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
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vdev->config->get(vdev,
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offsetof(struct virtio_9p_config, tag_len),
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&tag_len, sizeof(tag_len));
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} else {
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err = -EINVAL;
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goto out_free_vq;
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}
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tag = kmalloc(tag_len, GFP_KERNEL);
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if (!tag) {
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err = -ENOMEM;
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goto out_free_vq;
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}
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vdev->config->get(vdev, offsetof(struct virtio_9p_config, tag),
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tag, tag_len);
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chan->tag = tag;
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chan->tag_len = tag_len;
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err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
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if (err) {
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goto out_free_tag;
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}
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chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
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if (!chan->vc_wq) {
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err = -ENOMEM;
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goto out_free_tag;
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}
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init_waitqueue_head(chan->vc_wq);
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chan->ring_bufs_avail = 1;
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/* Ceiling limit to avoid denial of service attacks */
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chan->p9_max_pages = nr_free_buffer_pages()/4;
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mutex_lock(&virtio_9p_lock);
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list_add_tail(&chan->chan_list, &virtio_chan_list);
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mutex_unlock(&virtio_9p_lock);
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return 0;
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out_free_tag:
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kfree(tag);
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out_free_vq:
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vdev->config->del_vqs(vdev);
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kfree(chan);
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fail:
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|
return err;
|
|
}
|
|
|
|
|
|
/**
|
|
* p9_virtio_create - allocate a new virtio channel
|
|
* @client: client instance invoking this transport
|
|
* @devname: string identifying the channel to connect to (unused)
|
|
* @args: args passed from sys_mount() for per-transport options (unused)
|
|
*
|
|
* This sets up a transport channel for 9p communication. Right now
|
|
* we only match the first available channel, but eventually we couldlook up
|
|
* alternate channels by matching devname versus a virtio_config entry.
|
|
* We use a simple reference count mechanism to ensure that only a single
|
|
* mount has a channel open at a time.
|
|
*
|
|
*/
|
|
|
|
static int
|
|
p9_virtio_create(struct p9_client *client, const char *devname, char *args)
|
|
{
|
|
struct virtio_chan *chan;
|
|
int ret = -ENOENT;
|
|
int found = 0;
|
|
|
|
mutex_lock(&virtio_9p_lock);
|
|
list_for_each_entry(chan, &virtio_chan_list, chan_list) {
|
|
if (!strncmp(devname, chan->tag, chan->tag_len) &&
|
|
strlen(devname) == chan->tag_len) {
|
|
if (!chan->inuse) {
|
|
chan->inuse = true;
|
|
found = 1;
|
|
break;
|
|
}
|
|
ret = -EBUSY;
|
|
}
|
|
}
|
|
mutex_unlock(&virtio_9p_lock);
|
|
|
|
if (!found) {
|
|
printk(KERN_ERR "9p: no channels available\n");
|
|
return ret;
|
|
}
|
|
|
|
client->trans = (void *)chan;
|
|
client->status = Connected;
|
|
chan->client = client;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* p9_virtio_remove - clean up resources associated with a virtio device
|
|
* @vdev: virtio device to remove
|
|
*
|
|
*/
|
|
|
|
static void p9_virtio_remove(struct virtio_device *vdev)
|
|
{
|
|
struct virtio_chan *chan = vdev->priv;
|
|
|
|
BUG_ON(chan->inuse);
|
|
vdev->config->del_vqs(vdev);
|
|
|
|
mutex_lock(&virtio_9p_lock);
|
|
list_del(&chan->chan_list);
|
|
mutex_unlock(&virtio_9p_lock);
|
|
sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
|
|
kfree(chan->tag);
|
|
kfree(chan->vc_wq);
|
|
kfree(chan);
|
|
|
|
}
|
|
|
|
static struct virtio_device_id id_table[] = {
|
|
{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
|
|
{ 0 },
|
|
};
|
|
|
|
static unsigned int features[] = {
|
|
VIRTIO_9P_MOUNT_TAG,
|
|
};
|
|
|
|
/* The standard "struct lguest_driver": */
|
|
static struct virtio_driver p9_virtio_drv = {
|
|
.feature_table = features,
|
|
.feature_table_size = ARRAY_SIZE(features),
|
|
.driver.name = KBUILD_MODNAME,
|
|
.driver.owner = THIS_MODULE,
|
|
.id_table = id_table,
|
|
.probe = p9_virtio_probe,
|
|
.remove = p9_virtio_remove,
|
|
};
|
|
|
|
static struct p9_trans_module p9_virtio_trans = {
|
|
.name = "virtio",
|
|
.create = p9_virtio_create,
|
|
.close = p9_virtio_close,
|
|
.request = p9_virtio_request,
|
|
.cancel = p9_virtio_cancel,
|
|
.maxsize = PAGE_SIZE*16,
|
|
.pref = P9_TRANS_PREF_PAYLOAD_SEP,
|
|
.def = 0,
|
|
.owner = THIS_MODULE,
|
|
};
|
|
|
|
/* The standard init function */
|
|
static int __init p9_virtio_init(void)
|
|
{
|
|
INIT_LIST_HEAD(&virtio_chan_list);
|
|
|
|
v9fs_register_trans(&p9_virtio_trans);
|
|
return register_virtio_driver(&p9_virtio_drv);
|
|
}
|
|
|
|
static void __exit p9_virtio_cleanup(void)
|
|
{
|
|
unregister_virtio_driver(&p9_virtio_drv);
|
|
v9fs_unregister_trans(&p9_virtio_trans);
|
|
}
|
|
|
|
module_init(p9_virtio_init);
|
|
module_exit(p9_virtio_cleanup);
|
|
|
|
MODULE_DEVICE_TABLE(virtio, id_table);
|
|
MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
|
|
MODULE_DESCRIPTION("Virtio 9p Transport");
|
|
MODULE_LICENSE("GPL");
|