Bunch of small fixes:

- three W=1 warning fixes: the NULL -> "" replacement isn't trivial
 but is serialized identically by the protocol layer and has been tested
 - one syzbot/KCSAN datarace annotation where we don't care about users
 messing with the fd they passed to mount -t 9p
 - removing a declaration without implementation
 - yet another race fix for trans_fd around connection close:
 the 'err' field is also used in potentially racy calls and this
 isn't complete, but it's better than what we have.
 - and finally a theorical memory leak fix on serialization failure
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Merge tag '9p-for-6.7-rc1' of https://github.com/martinetd/linux

Pull 9p updates from Dominique Martinet:
 A bunch of small fixes:

   - three W=1 warning fixes: the NULL -> "" replacement isn't trivial
     but is serialized identically by the protocol layer and has been
     tested

   - one syzbot/KCSAN datarace annotation where we don't care about
     users messing with the fd they passed to mount -t 9p

   - removing a declaration without implementation

   - yet another race fix for trans_fd around connection close: the
     'err' field is also used in potentially racy calls and this isn't
     complete, but it's better than what we had

   - and finally a theorical memory leak fix on serialization failure"

* tag '9p-for-6.7-rc1' of https://github.com/martinetd/linux:
  9p/net: fix possible memory leak in p9_check_errors()
  9p/fs: add MODULE_DESCRIPTION
  9p/net: xen: fix false positive printf format overflow warning
  9p: v9fs_listxattr: fix %s null argument warning
  9p/trans_fd: Annotate data-racy writes to file::f_flags
  fs/9p: Remove unused function declaration v9fs_inode2stat()
  9p/trans_fd: avoid sending req to a cancelled conn

fs/9p/v9fs.c

@@ -732,4 +732,5 @@ module_exit(exit_v9fs)
 MODULE_AUTHOR("Latchesar Ionkov <lucho@ionkov.net>");
 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 MODULE_AUTHOR("Ron Minnich <rminnich@lanl.gov>");
+MODULE_DESCRIPTION("9P Client File System");
 MODULE_LICENSE("GPL");

fs/9p/v9fs_vfs.h

@@ -52,7 +52,6 @@ void v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode,
 			   unsigned int flags);
 int v9fs_dir_release(struct inode *inode, struct file *filp);
 int v9fs_file_open(struct inode *inode, struct file *file);
-void v9fs_inode2stat(struct inode *inode, struct p9_wstat *stat);
 int v9fs_uflags2omode(int uflags, int extended);
 
 void v9fs_blank_wstat(struct p9_wstat *wstat);

fs/9p/xattr.c

@@ -68,7 +68,7 @@ ssize_t v9fs_xattr_get(struct dentry *dentry, const char *name,
 	struct p9_fid *fid;
 	int ret;
 
-	p9_debug(P9_DEBUG_VFS, "name = %s value_len = %zu\n",
+	p9_debug(P9_DEBUG_VFS, "name = '%s' value_len = %zu\n",
 		 name, buffer_size);
 	fid = v9fs_fid_lookup(dentry);
 	if (IS_ERR(fid))
@@ -139,7 +139,8 @@ int v9fs_fid_xattr_set(struct p9_fid *fid, const char *name,
 
 ssize_t v9fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 {
-	return v9fs_xattr_get(dentry, NULL, buffer, buffer_size);
+	/* Txattrwalk with an empty string lists xattrs instead */
+	return v9fs_xattr_get(dentry, "", buffer, buffer_size);
 }
 
 static int v9fs_xattr_handler_get(const struct xattr_handler *handler,

net/9p/client.c

@@ -540,12 +540,14 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
 		return 0;
 
 	if (!p9_is_proto_dotl(c)) {
-		char *ename;
+		char *ename = NULL;
 
 		err = p9pdu_readf(&req->rc, c->proto_version, "s?d",
 				  &ename, &ecode);
-		if (err)
+		if (err) {
+			kfree(ename);
 			goto out_err;
+		}
 
 		if (p9_is_proto_dotu(c) && ecode < 512)
 			err = -ecode;
@@ -1979,7 +1981,7 @@ struct p9_fid *p9_client_xattrwalk(struct p9_fid *file_fid,
 		goto error;
 	}
 	p9_debug(P9_DEBUG_9P,
-		 ">>> TXATTRWALK file_fid %d, attr_fid %d name %s\n",
+		 ">>> TXATTRWALK file_fid %d, attr_fid %d name '%s'\n",
 		 file_fid->fid, attr_fid->fid, attr_name);
 
 	req = p9_client_rpc(clnt, P9_TXATTRWALK, "dds",

net/9p/trans_fd.c

@@ -671,10 +671,14 @@ static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
 
 	p9_debug(P9_DEBUG_TRANS, "mux %p task %p tcall %p id %d\n",
 		 m, current, &req->tc, req->tc.id);
-	if (m->err < 0)
-		return m->err;
 
 	spin_lock(&m->req_lock);
+
+	if (m->err < 0) {
+		spin_unlock(&m->req_lock);
+		return m->err;
+	}
+
 	WRITE_ONCE(req->status, REQ_STATUS_UNSENT);
 	list_add_tail(&req->req_list, &m->unsent_req_list);
 	spin_unlock(&m->req_lock);
@@ -832,14 +836,21 @@ static int p9_fd_open(struct p9_client *client, int rfd, int wfd)
 		goto out_free_ts;
 	if (!(ts->rd->f_mode & FMODE_READ))
 		goto out_put_rd;
-	/* prevent workers from hanging on IO when fd is a pipe */
-	ts->rd->f_flags |= O_NONBLOCK;
+	/* Prevent workers from hanging on IO when fd is a pipe.
+	 * It's technically possible for userspace or concurrent mounts to
+	 * modify this flag concurrently, which will likely result in a
+	 * broken filesystem. However, just having bad flags here should
+	 * not crash the kernel or cause any other sort of bug, so mark this
+	 * particular data race as intentional so that tooling (like KCSAN)
+	 * can allow it and detect further problems.
+	 */
+	data_race(ts->rd->f_flags |= O_NONBLOCK);
 	ts->wr = fget(wfd);
 	if (!ts->wr)
 		goto out_put_rd;
 	if (!(ts->wr->f_mode & FMODE_WRITE))
 		goto out_put_wr;
-	ts->wr->f_flags |= O_NONBLOCK;
+	data_race(ts->wr->f_flags |= O_NONBLOCK);
 
 	client->trans = ts;
 	client->status = Connected;

net/9p/trans_xen.c

@@ -54,7 +54,6 @@ struct xen_9pfs_front_priv {
 	char *tag;
 	struct p9_client *client;
 
-	int num_rings;
 	struct xen_9pfs_dataring *rings;
 };
 
@@ -131,7 +130,7 @@ static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 	if (list_entry_is_head(priv, &xen_9pfs_devs, list))
 		return -EINVAL;
 
-	num = p9_req->tc.tag % priv->num_rings;
+	num = p9_req->tc.tag % XEN_9PFS_NUM_RINGS;
 	ring = &priv->rings[num];
 
 again:
@@ -279,7 +278,7 @@ static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 	list_del(&priv->list);
 	write_unlock(&xen_9pfs_lock);
 
-	for (i = 0; i < priv->num_rings; i++) {
+	for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
 		struct xen_9pfs_dataring *ring = &priv->rings[i];
 
 		cancel_work_sync(&ring->work);
@@ -408,15 +407,14 @@ static int xen_9pfs_front_init(struct xenbus_device *dev)
 	if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
 		p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
 
-	priv->num_rings = XEN_9PFS_NUM_RINGS;
-	priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
+	priv->rings = kcalloc(XEN_9PFS_NUM_RINGS, sizeof(*priv->rings),
 			      GFP_KERNEL);
 	if (!priv->rings) {
 		kfree(priv);
 		return -ENOMEM;
 	}
 
-	for (i = 0; i < priv->num_rings; i++) {
+	for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
 		priv->rings[i].priv = priv;
 		ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
 						    max_ring_order);
@@ -434,10 +432,11 @@ static int xen_9pfs_front_init(struct xenbus_device *dev)
 	if (ret)
 		goto error_xenbus;
 	ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
-			    priv->num_rings);
+			    XEN_9PFS_NUM_RINGS);
 	if (ret)
 		goto error_xenbus;
-	for (i = 0; i < priv->num_rings; i++) {
+
+	for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
 		char str[16];
 
 		BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);