Merge tag '9p-for-4.19-2' of git://github.com/martinetd/linux

Pull 9p updates from Dominique Martinet:
 "This contains mostly fixes (6 to be backported to stable) and a few
  changes, here is the breakdown:

   - rework how fids are attributed by replacing some custom tracking in
     a list by an idr

   - for packet-based transports (virtio/rdma) validate that the packet
     length matches what the header says

   - a few race condition fixes found by syzkaller

   - missing argument check when NULL device is passed in sys_mount

   - a few virtio fixes

   - some spelling and style fixes"

* tag '9p-for-4.19-2' of git://github.com/martinetd/linux: (21 commits)
  net/9p/trans_virtio.c: add null terminal for mount tag
  9p/virtio: fix off-by-one error in sg list bounds check
  9p: fix whitespace issues
  9p: fix multiple NULL-pointer-dereferences
  fs/9p/xattr.c: catch the error of p9_client_clunk when setting xattr failed
  9p: validate PDU length
  net/9p/trans_fd.c: fix race by holding the lock
  net/9p/trans_fd.c: fix race-condition by flushing workqueue before the kfree()
  net/9p/virtio: Fix hard lockup in req_done
  net/9p/trans_virtio.c: fix some spell mistakes in comments
  9p/net: Fix zero-copy path in the 9p virtio transport
  9p: Embed wait_queue_head into p9_req_t
  9p: Replace the fidlist with an IDR
  9p: Change p9_fid_create calling convention
  9p: Fix comment on smp_wmb
  net/9p/client.c: version pointer uninitialized
  fs/9p/v9fs.c: fix spelling mistake "Uknown" -> "Unknown"
  net/9p: fix error path of p9_virtio_probe
  9p/net/protocol.c: return -ENOMEM when kmalloc() failed
  net/9p/client.c: add missing '\n' at the end of p9_debug()
  ...

7 files changed, 112 insertions, 105 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index 5c1343195292..deae53a7dffc 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -283,8 +283,9 @@ p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
 				return ERR_PTR(-ENOMEM);
 			}
 			for (col = 0; col < P9_ROW_MAXTAG; col++) {
-				c->reqs[row][col].status = REQ_STATUS_IDLE;
-				c->reqs[row][col].tc = NULL;
+				req = &c->reqs[row][col];
+				req->status = REQ_STATUS_IDLE;
+				init_waitqueue_head(&req->wq);
 			}
 			c->max_tag += P9_ROW_MAXTAG;
 		}
@@ -294,13 +295,6 @@ p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
 	col = tag % P9_ROW_MAXTAG;
 
 	req = &c->reqs[row][col];
-	if (!req->wq) {
-		req->wq = kmalloc(sizeof(wait_queue_head_t), GFP_NOFS);
-		if (!req->wq)
-			goto grow_failed;
-		init_waitqueue_head(req->wq);
-	}
-
 	if (!req->tc)
 		req->tc = p9_fcall_alloc(alloc_msize);
 	if (!req->rc)
@@ -320,9 +314,7 @@ grow_failed:
 	pr_err("Couldn't grow tag array\n");
 	kfree(req->tc);
 	kfree(req->rc);
-	kfree(req->wq);
 	req->tc = req->rc = NULL;
-	req->wq = NULL;
 	return ERR_PTR(-ENOMEM);
 }
 
@@ -341,7 +333,7 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
 	 * buffer to read the data into */
 	tag++;
 
-	if(tag >= c->max_tag) 
+	if (tag >= c->max_tag)
 		return NULL;
 
 	row = tag / P9_ROW_MAXTAG;
@@ -410,7 +402,6 @@ static void p9_tag_cleanup(struct p9_client *c)
 	/* free requests associated with tags */
 	for (row = 0; row < (c->max_tag/P9_ROW_MAXTAG); row++) {
 		for (col = 0; col < P9_ROW_MAXTAG; col++) {
-			kfree(c->reqs[row][col].wq);
 			kfree(c->reqs[row][col].tc);
 			kfree(c->reqs[row][col].rc);
 		}
@@ -448,12 +439,12 @@ void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status)
 
 	/*
 	 * This barrier is needed to make sure any change made to req before
-	 * the other thread wakes up will indeed be seen by the waiting side.
+	 * the status change is visible to another thread
 	 */
 	smp_wmb();
 	req->status = status;
 
-	wake_up(req->wq);
+	wake_up(&req->wq);
 	p9_debug(P9_DEBUG_MUX, "wakeup: %d\n", req->tc->tag);
 }
 EXPORT_SYMBOL(p9_client_cb);
@@ -478,20 +469,11 @@ p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type, int16_t *tag,
 	int err;
 
 	pdu->offset = 0;
-	if (pdu->size == 0)
-		pdu->size = 7;
 
 	err = p9pdu_readf(pdu, 0, "dbw", &r_size, &r_type, &r_tag);
 	if (err)
 		goto rewind_and_exit;
 
-	pdu->size = r_size;
-	pdu->id = r_type;
-	pdu->tag = r_tag;
-
-	p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
-		 pdu->size, pdu->id, pdu->tag);
-
 	if (type)
 		*type = r_type;
 	if (tag)
@@ -499,6 +481,16 @@ p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type, int16_t *tag,
 	if (size)
 		*size = r_size;
 
+	if (pdu->size != r_size || r_size < 7) {
+		err = -EINVAL;
+		goto rewind_and_exit;
+	}
+
+	pdu->id = r_type;
+	pdu->tag = r_tag;
+
+	p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
+		 pdu->size, pdu->id, pdu->tag);
 
 rewind_and_exit:
 	if (rewind)
@@ -525,6 +517,12 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
 	int ecode;
 
 	err = p9_parse_header(req->rc, NULL, &type, NULL, 0);
+	if (req->rc->size >= c->msize) {
+		p9_debug(P9_DEBUG_ERROR,
+			 "requested packet size too big: %d\n",
+			 req->rc->size);
+		return -EIO;
+	}
 	/*
 	 * dump the response from server
 	 * This should be after check errors which poplulate pdu_fcall.
@@ -774,7 +772,7 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 	}
 again:
 	/* Wait for the response */
-	err = wait_event_killable(*req->wq, req->status >= REQ_STATUS_RCVD);
+	err = wait_event_killable(req->wq, req->status >= REQ_STATUS_RCVD);
 
 	/*
 	 * Make sure our req is coherent with regard to updates in other
@@ -909,34 +907,31 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 {
 	int ret;
 	struct p9_fid *fid;
-	unsigned long flags;
 
 	p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
 	fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
 	if (!fid)
-		return ERR_PTR(-ENOMEM);
-
-	ret = p9_idpool_get(clnt->fidpool);
-	if (ret < 0) {
-		ret = -ENOSPC;
-		goto error;
-	}
-	fid->fid = ret;
+		return NULL;
 
 	memset(&fid->qid, 0, sizeof(struct p9_qid));
 	fid->mode = -1;
 	fid->uid = current_fsuid();
 	fid->clnt = clnt;
 	fid->rdir = NULL;
-	spin_lock_irqsave(&clnt->lock, flags);
-	list_add(&fid->flist, &clnt->fidlist);
-	spin_unlock_irqrestore(&clnt->lock, flags);
+	fid->fid = 0;
 
-	return fid;
+	idr_preload(GFP_KERNEL);
+	spin_lock_irq(&clnt->lock);
+	ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
+			    GFP_NOWAIT);
+	spin_unlock_irq(&clnt->lock);
+	idr_preload_end();
+
+	if (!ret)
+		return fid;
 
-error:
 	kfree(fid);
-	return ERR_PTR(ret);
+	return NULL;
 }
 
 static void p9_fid_destroy(struct p9_fid *fid)
@@ -946,9 +941,8 @@ static void p9_fid_destroy(struct p9_fid *fid)
 
 	p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
 	clnt = fid->clnt;
-	p9_idpool_put(fid->fid, clnt->fidpool);
 	spin_lock_irqsave(&clnt->lock, flags);
-	list_del(&fid->flist);
+	idr_remove(&clnt->fids, fid->fid);
 	spin_unlock_irqrestore(&clnt->lock, flags);
 	kfree(fid->rdir);
 	kfree(fid);
@@ -958,7 +952,7 @@ static int p9_client_version(struct p9_client *c)
 {
 	int err = 0;
 	struct p9_req_t *req;
-	char *version;
+	char *version = NULL;
 	int msize;
 
 	p9_debug(P9_DEBUG_9P, ">>> TVERSION msize %d protocol %d\n",
@@ -1031,7 +1025,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 	memcpy(clnt->name, client_id, strlen(client_id) + 1);
 
 	spin_lock_init(&clnt->lock);
-	INIT_LIST_HEAD(&clnt->fidlist);
+	idr_init(&clnt->fids);
 
 	err = p9_tag_init(clnt);
 	if (err < 0)
@@ -1051,18 +1045,12 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 		goto destroy_tagpool;
 	}
 
-	clnt->fidpool = p9_idpool_create();
-	if (IS_ERR(clnt->fidpool)) {
-		err = PTR_ERR(clnt->fidpool);
-		goto put_trans;
-	}
-
 	p9_debug(P9_DEBUG_MUX, "clnt %p trans %p msize %d protocol %d\n",
 		 clnt, clnt->trans_mod, clnt->msize, clnt->proto_version);
 
 	err = clnt->trans_mod->create(clnt, dev_name, options);
 	if (err)
-		goto destroy_fidpool;
+		goto put_trans;
 
 	if (clnt->msize > clnt->trans_mod->maxsize)
 		clnt->msize = clnt->trans_mod->maxsize;
@@ -1075,8 +1063,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 
 close_trans:
 	clnt->trans_mod->close(clnt);
-destroy_fidpool:
-	p9_idpool_destroy(clnt->fidpool);
 put_trans:
 	v9fs_put_trans(clnt->trans_mod);
 destroy_tagpool:
@@ -1089,7 +1075,8 @@ EXPORT_SYMBOL(p9_client_create);
 
 void p9_client_destroy(struct p9_client *clnt)
 {
-	struct p9_fid *fid, *fidptr;
+	struct p9_fid *fid;
+	int id;
 
 	p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);
 
@@ -1098,14 +1085,11 @@ void p9_client_destroy(struct p9_client *clnt)
 
 	v9fs_put_trans(clnt->trans_mod);
 
-	list_for_each_entry_safe(fid, fidptr, &clnt->fidlist, flist) {
+	idr_for_each_entry(&clnt->fids, fid, id) {
 		pr_info("Found fid %d not clunked\n", fid->fid);
 		p9_fid_destroy(fid);
 	}
 
-	if (clnt->fidpool)
-		p9_idpool_destroy(clnt->fidpool);
-
 	p9_tag_cleanup(clnt);
 
 	kfree(clnt);
@@ -1138,9 +1122,8 @@ struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
 	p9_debug(P9_DEBUG_9P, ">>> TATTACH afid %d uname %s aname %s\n",
 		 afid ? afid->fid : -1, uname, aname);
 	fid = p9_fid_create(clnt);
-	if (IS_ERR(fid)) {
-		err = PTR_ERR(fid);
-		fid = NULL;
+	if (!fid) {
+		err = -ENOMEM;
 		goto error;
 	}
 	fid->uid = n_uname;
@@ -1189,9 +1172,8 @@ struct p9_fid *p9_client_walk(struct p9_fid *oldfid, uint16_t nwname,
 	clnt = oldfid->clnt;
 	if (clone) {
 		fid = p9_fid_create(clnt);
-		if (IS_ERR(fid)) {
-			err = PTR_ERR(fid);
-			fid = NULL;
+		if (!fid) {
+			err = -ENOMEM;
 			goto error;
 		}
 
@@ -1576,7 +1558,7 @@ p9_client_read(struct p9_fid *fid, u64 offset, struct iov_iter *to, int *err)
 		int count = iov_iter_count(to);
 		int rsize, non_zc = 0;
 		char *dataptr;
-			
+
 		rsize = fid->iounit;
 		if (!rsize || rsize > clnt->msize-P9_IOHDRSZ)
 			rsize = clnt->msize - P9_IOHDRSZ;
@@ -1790,7 +1772,7 @@ struct p9_stat_dotl *p9_client_getattr_dotl(struct p9_fid *fid,
 		"<<< st_mtime_sec=%lld st_mtime_nsec=%lld\n"
 		"<<< st_ctime_sec=%lld st_ctime_nsec=%lld\n"
 		"<<< st_btime_sec=%lld st_btime_nsec=%lld\n"
-		"<<< st_gen=%lld st_data_version=%lld",
+		"<<< st_gen=%lld st_data_version=%lld\n",
 		ret->st_result_mask, ret->qid.type, ret->qid.path,
 		ret->qid.version, ret->st_mode, ret->st_nlink,
 		from_kuid(&init_user_ns, ret->st_uid),
@@ -2019,9 +2001,8 @@ struct p9_fid *p9_client_xattrwalk(struct p9_fid *file_fid,
 	err = 0;
 	clnt = file_fid->clnt;
 	attr_fid = p9_fid_create(clnt);
-	if (IS_ERR(attr_fid)) {
-		err = PTR_ERR(attr_fid);
-		attr_fid = NULL;
+	if (!attr_fid) {
+		err = -ENOMEM;
 		goto error;
 	}
 	p9_debug(P9_DEBUG_9P,
diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 931ea00c4fed..4a1e1dd30b52 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -156,7 +156,7 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 
 				*sptr = kmalloc(len + 1, GFP_NOFS);
 				if (*sptr == NULL) {
-					errcode = -EFAULT;
+					errcode = -ENOMEM;
 					break;
 				}
 				if (pdu_read(pdu, *sptr, len)) {
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 588bf88c3305..e2ef3c782c53 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -185,6 +185,8 @@ static void p9_mux_poll_stop(struct p9_conn *m)
 	spin_lock_irqsave(&p9_poll_lock, flags);
 	list_del_init(&m->poll_pending_link);
 	spin_unlock_irqrestore(&p9_poll_lock, flags);
+
+	flush_work(&p9_poll_work);
 }
 
 /**
@@ -197,15 +199,14 @@ static void p9_mux_poll_stop(struct p9_conn *m)
 static void p9_conn_cancel(struct p9_conn *m, int err)
 {
 	struct p9_req_t *req, *rtmp;
-	unsigned long flags;
 	LIST_HEAD(cancel_list);
 
 	p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);
 
-	spin_lock_irqsave(&m->client->lock, flags);
+	spin_lock(&m->client->lock);
 
 	if (m->err) {
-		spin_unlock_irqrestore(&m->client->lock, flags);
+		spin_unlock(&m->client->lock);
 		return;
 	}
 
@@ -217,7 +218,6 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
 	list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) {
 		list_move(&req->req_list, &cancel_list);
 	}
-	spin_unlock_irqrestore(&m->client->lock, flags);
 
 	list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
 		p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
@@ -226,6 +226,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
 			req->t_err = err;
 		p9_client_cb(m->client, req, REQ_STATUS_ERROR);
 	}
+	spin_unlock(&m->client->lock);
 }
 
 static __poll_t
@@ -324,7 +325,9 @@ static void p9_read_work(struct work_struct *work)
 	if ((!m->req) && (m->rc.offset == m->rc.capacity)) {
 		p9_debug(P9_DEBUG_TRANS, "got new header\n");
 
-		err = p9_parse_header(&m->rc, NULL, NULL, NULL, 0);
+		/* Header size */
+		m->rc.size = 7;
+		err = p9_parse_header(&m->rc, &m->rc.size, NULL, NULL, 0);
 		if (err) {
 			p9_debug(P9_DEBUG_ERROR,
 				 "error parsing header: %d\n", err);
@@ -369,12 +372,14 @@ static void p9_read_work(struct work_struct *work)
 	 */
 	if ((m->req) && (m->rc.offset == m->rc.capacity)) {
 		p9_debug(P9_DEBUG_TRANS, "got new packet\n");
+		m->req->rc->size = m->rc.offset;
 		spin_lock(&m->client->lock);
 		if (m->req->status != REQ_STATUS_ERROR)
 			status = REQ_STATUS_RCVD;
 		list_del(&m->req->req_list);
-		spin_unlock(&m->client->lock);
+		/* update req->status while holding client->lock  */
 		p9_client_cb(m->client, m->req, status);
+		spin_unlock(&m->client->lock);
 		m->rc.sdata = NULL;
 		m->rc.offset = 0;
 		m->rc.capacity = 0;
@@ -940,7 +945,7 @@ p9_fd_create_tcp(struct p9_client *client, const char *addr, char *args)
 	if (err < 0)
 		return err;
 
-	if (valid_ipaddr4(addr) < 0)
+	if (addr == NULL || valid_ipaddr4(addr) < 0)
 		return -EINVAL;
 
 	csocket = NULL;
@@ -990,6 +995,9 @@ p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
 
 	csocket = NULL;
 
+	if (addr == NULL)
+		return -EINVAL;
+
 	if (strlen(addr) >= UNIX_PATH_MAX) {
 		pr_err("%s (%d): address too long: %s\n",
 		       __func__, task_pid_nr(current), addr);
diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
index b06286f253cb..b513cffeeb3c 100644
--- a/net/9p/trans_rdma.c
+++ b/net/9p/trans_rdma.c
@@ -320,6 +320,7 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc)
 	if (wc->status != IB_WC_SUCCESS)
 		goto err_out;
 
+	c->rc->size = wc->byte_len;
 	err = p9_parse_header(c->rc, NULL, NULL, &tag, 1);
 	if (err)
 		goto err_out;
@@ -644,6 +645,9 @@ rdma_create_trans(struct p9_client *client, const char *addr, char *args)
 	struct rdma_conn_param conn_param;
 	struct ib_qp_init_attr qp_attr;
 
+	if (addr == NULL)
+		return -EINVAL;
+
 	/* Parse the transport specific mount options */
 	err = parse_opts(args, &opts);
 	if (err < 0)
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 05006cbb3361..7728b0acde09 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -89,10 +89,8 @@ struct virtio_chan {
 	unsigned long p9_max_pages;
 	/* Scatterlist: can be too big for stack. */
 	struct scatterlist sg[VIRTQUEUE_NUM];
-
-	int tag_len;
 	/*
-	 * tag name to identify a mount Non-null terminated
+	 * tag name to identify a mount null terminated
 	 */
 	char *tag;
 
@@ -144,24 +142,27 @@ static void req_done(struct virtqueue *vq)
 	struct virtio_chan *chan = vq->vdev->priv;
 	unsigned int len;
 	struct p9_req_t *req;
+	bool need_wakeup = false;
 	unsigned long flags;
 
 	p9_debug(P9_DEBUG_TRANS, ": request done\n");
 
-	while (1) {
-		spin_lock_irqsave(&chan->lock, flags);
-		req = virtqueue_get_buf(chan->vq, &len);
-		if (req == NULL) {
-			spin_unlock_irqrestore(&chan->lock, flags);
-			break;
+	spin_lock_irqsave(&chan->lock, flags);
+	while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) {
+		if (!chan->ring_bufs_avail) {
+			chan->ring_bufs_avail = 1;
+			need_wakeup = true;
 		}
-		chan->ring_bufs_avail = 1;
-		spin_unlock_irqrestore(&chan->lock, flags);
-		/* Wakeup if anyone waiting for VirtIO ring space. */
-		wake_up(chan->vc_wq);
-		if (len)
+
+		if (len) {
+			req->rc->size = len;
 			p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
+		}
 	}
+	spin_unlock_irqrestore(&chan->lock, flags);
+	/* Wakeup if anyone waiting for VirtIO ring space. */
+	if (need_wakeup)
+		wake_up(chan->vc_wq);
 }
 
 /**
@@ -188,7 +189,7 @@ static int pack_sg_list(struct scatterlist *sg, int start,
 		s = rest_of_page(data);
 		if (s > count)
 			s = count;
-		BUG_ON(index > limit);
+		BUG_ON(index >= limit);
 		/* Make sure we don't terminate early. */
 		sg_unmark_end(&sg[index]);
 		sg_set_buf(&sg[index++], data, s);
@@ -233,6 +234,7 @@ pack_sg_list_p(struct scatterlist *sg, int start, int limit,
 		s = PAGE_SIZE - data_off;
 		if (s > count)
 			s = count;
+		BUG_ON(index >= limit);
 		/* Make sure we don't terminate early. */
 		sg_unmark_end(&sg[index]);
 		sg_set_page(&sg[index++], pdata[i++], s, data_off);
@@ -382,8 +384,8 @@ static int p9_get_mapped_pages(struct virtio_chan *chan,
  * p9_virtio_zc_request - issue a zero copy request
  * @client: client instance issuing the request
  * @req: request to be issued
- * @uidata: user bffer that should be ued for zero copy read
- * @uodata: user buffer that shoud be user for zero copy write
+ * @uidata: user buffer that should be used for zero copy read
+ * @uodata: user buffer that should be used for zero copy write
  * @inlen: read buffer size
  * @outlen: write buffer size
  * @in_hdr_len: reader header size, This is the size of response protocol data
@@ -406,6 +408,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 	p9_debug(P9_DEBUG_TRANS, "virtio request\n");
 
 	if (uodata) {
+		__le32 sz;
 		int n = p9_get_mapped_pages(chan, &out_pages, uodata,
 					    outlen, &offs, &need_drop);
 		if (n < 0)
@@ -416,6 +419,12 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 			memcpy(&req->tc->sdata[req->tc->size - 4], &v, 4);
 			outlen = n;
 		}
+		/* The size field of the message must include the length of the
+		 * header and the length of the data.  We didn't actually know
+		 * the length of the data until this point so add it in now.
+		 */
+		sz = cpu_to_le32(req->tc->size + outlen);
+		memcpy(&req->tc->sdata[0], &sz, sizeof(sz));
 	} else if (uidata) {
 		int n = p9_get_mapped_pages(chan, &in_pages, uidata,
 					    inlen, &offs, &need_drop);
@@ -446,7 +455,7 @@ req_retry_pinned:
 		out += pack_sg_list_p(chan->sg, out, VIRTQUEUE_NUM,
 				      out_pages, out_nr_pages, offs, outlen);
 	}
-		
+
 	/*
 	 * Take care of in data
 	 * For example TREAD have 11.
@@ -490,7 +499,7 @@ req_retry_pinned:
 	virtqueue_kick(chan->vq);
 	spin_unlock_irqrestore(&chan->lock, flags);
 	p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
-	err = wait_event_killable(*req->wq, req->status >= REQ_STATUS_RCVD);
+	err = wait_event_killable(req->wq, req->status >= REQ_STATUS_RCVD);
 	/*
 	 * Non kernel buffers are pinned, unpin them
 	 */
@@ -517,14 +526,15 @@ static ssize_t p9_mount_tag_show(struct device *dev,
 {
 	struct virtio_chan *chan;
 	struct virtio_device *vdev;
+	int tag_len;
 
 	vdev = dev_to_virtio(dev);
 	chan = vdev->priv;
+	tag_len = strlen(chan->tag);
 
-	memcpy(buf, chan->tag, chan->tag_len);
-	buf[chan->tag_len] = 0;
+	memcpy(buf, chan->tag, tag_len + 1);
 
-	return chan->tag_len + 1;
+	return tag_len + 1;
 }
 
 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
@@ -563,7 +573,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
 	chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
 	if (IS_ERR(chan->vq)) {
 		err = PTR_ERR(chan->vq);
-		goto out_free_vq;
+		goto out_free_chan;
 	}
 	chan->vq->vdev->priv = chan;
 	spin_lock_init(&chan->lock);
@@ -577,7 +587,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
 		err = -EINVAL;
 		goto out_free_vq;
 	}
-	tag = kmalloc(tag_len, GFP_KERNEL);
+	tag = kzalloc(tag_len + 1, GFP_KERNEL);
 	if (!tag) {
 		err = -ENOMEM;
 		goto out_free_vq;
@@ -586,7 +596,6 @@ static int p9_virtio_probe(struct virtio_device *vdev)
 	virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
 			   tag, tag_len);
 	chan->tag = tag;
-	chan->tag_len = tag_len;
 	err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
 	if (err) {
 		goto out_free_tag;
@@ -616,6 +625,7 @@ out_free_tag:
 	kfree(tag);
 out_free_vq:
 	vdev->config->del_vqs(vdev);
+out_free_chan:
 	kfree(chan);
 fail:
 	return err;
@@ -643,10 +653,12 @@ p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 	int ret = -ENOENT;
 	int found = 0;
 
+	if (devname == NULL)
+		return -EINVAL;
+
 	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 (!strcmp(devname, chan->tag)) {
 			if (!chan->inuse) {
 				chan->inuse = true;
 				found = 1;
diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 2e2b8bca54f3..c2d54ac76bfd 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -94,6 +94,9 @@ static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
 {
 	struct xen_9pfs_front_priv *priv;
 
+	if (addr == NULL)
+		return -EINVAL;
+
 	read_lock(&xen_9pfs_lock);
 	list_for_each_entry(priv, &xen_9pfs_devs, list) {
 		if (!strcmp(priv->tag, addr)) {
diff --git a/net/9p/util.c b/net/9p/util.c
index 59f278e64f58..55ad98277e85 100644
--- a/net/9p/util.c
+++ b/net/9p/util.c
@@ -138,4 +138,3 @@ int p9_idpool_check(int id, struct p9_idpool *p)
 	return idr_find(&p->pool, id) != NULL;
 }
 EXPORT_SYMBOL(p9_idpool_check);
-