1 files changed, 86 insertions, 52 deletions

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index df003bc67da0..5fd4fc49aef9 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -250,8 +250,8 @@ EXPORT_SYMBOL_GPL(ffs_lock);
 static struct ffs_dev *_ffs_find_dev(const char *name);
 static struct ffs_dev *_ffs_alloc_dev(void);
 static void _ffs_free_dev(struct ffs_dev *dev);
-static void *ffs_acquire_dev(const char *dev_name);
-static void ffs_release_dev(struct ffs_data *ffs_data);
+static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data);
+static void ffs_release_dev(struct ffs_dev *ffs_dev);
 static int ffs_ready(struct ffs_data *ffs);
 static void ffs_closed(struct ffs_data *ffs);
 
@@ -614,7 +614,7 @@ static int ffs_ep0_open(struct inode *inode, struct file *file)
 	file->private_data = ffs;
 	ffs_data_opened(ffs);
 
-	return 0;
+	return stream_open(inode, file);
 }
 
 static int ffs_ep0_release(struct inode *inode, struct file *file)
@@ -1156,7 +1156,7 @@ ffs_epfile_open(struct inode *inode, struct file *file)
 	file->private_data = epfile;
 	ffs_data_opened(epfile->ffs);
 
-	return 0;
+	return stream_open(inode, file);
 }
 
 static int ffs_aio_cancel(struct kiocb *kiocb)
@@ -1572,8 +1572,8 @@ unmapped_value:
 static int ffs_fs_get_tree(struct fs_context *fc)
 {
 	struct ffs_sb_fill_data *ctx = fc->fs_private;
-	void *ffs_dev;
 	struct ffs_data	*ffs;
+	int ret;
 
 	ENTER();
 
@@ -1592,13 +1592,12 @@ static int ffs_fs_get_tree(struct fs_context *fc)
 		return -ENOMEM;
 	}
 
-	ffs_dev = ffs_acquire_dev(ffs->dev_name);
-	if (IS_ERR(ffs_dev)) {
+	ret = ffs_acquire_dev(ffs->dev_name, ffs);
+	if (ret) {
 		ffs_data_put(ffs);
-		return PTR_ERR(ffs_dev);
+		return ret;
 	}
 
-	ffs->private_data = ffs_dev;
 	ctx->ffs_data = ffs;
 	return get_tree_nodev(fc, ffs_sb_fill);
 }
@@ -1609,7 +1608,6 @@ static void ffs_fs_free_fc(struct fs_context *fc)
 
 	if (ctx) {
 		if (ctx->ffs_data) {
-			ffs_release_dev(ctx->ffs_data);
 			ffs_data_put(ctx->ffs_data);
 		}
 
@@ -1648,10 +1646,8 @@ ffs_fs_kill_sb(struct super_block *sb)
 	ENTER();
 
 	kill_litter_super(sb);
-	if (sb->s_fs_info) {
-		ffs_release_dev(sb->s_fs_info);
+	if (sb->s_fs_info)
 		ffs_data_closed(sb->s_fs_info);
-	}
 }
 
 static struct file_system_type ffs_fs_type = {
@@ -1721,6 +1717,7 @@ static void ffs_data_put(struct ffs_data *ffs)
 	if (unlikely(refcount_dec_and_test(&ffs->ref))) {
 		pr_info("%s(): freeing\n", __func__);
 		ffs_data_clear(ffs);
+		ffs_release_dev(ffs->private_data);
 		BUG_ON(waitqueue_active(&ffs->ev.waitq) ||
 		       waitqueue_active(&ffs->ep0req_completion.wait) ||
 		       waitqueue_active(&ffs->wait));
@@ -1732,16 +1729,24 @@ static void ffs_data_put(struct ffs_data *ffs)
 
 static void ffs_data_closed(struct ffs_data *ffs)
 {
+	struct ffs_epfile *epfiles;
+	unsigned long flags;
+
 	ENTER();
 
 	if (atomic_dec_and_test(&ffs->opened)) {
 		if (ffs->no_disconnect) {
 			ffs->state = FFS_DEACTIVATED;
-			if (ffs->epfiles) {
-				ffs_epfiles_destroy(ffs->epfiles,
-						   ffs->eps_count);
-				ffs->epfiles = NULL;
-			}
+			spin_lock_irqsave(&ffs->eps_lock, flags);
+			epfiles = ffs->epfiles;
+			ffs->epfiles = NULL;
+			spin_unlock_irqrestore(&ffs->eps_lock,
+							flags);
+
+			if (epfiles)
+				ffs_epfiles_destroy(epfiles,
+						 ffs->eps_count);
+
 			if (ffs->setup_state == FFS_SETUP_PENDING)
 				__ffs_ep0_stall(ffs);
 		} else {
@@ -1788,17 +1793,34 @@ static struct ffs_data *ffs_data_new(const char *dev_name)
 
 static void ffs_data_clear(struct ffs_data *ffs)
 {
+	struct ffs_epfile *epfiles;
+	unsigned long flags;
+
 	ENTER();
 
 	ffs_closed(ffs);
 
 	BUG_ON(ffs->gadget);
 
-	if (ffs->epfiles)
-		ffs_epfiles_destroy(ffs->epfiles, ffs->eps_count);
+	spin_lock_irqsave(&ffs->eps_lock, flags);
+	epfiles = ffs->epfiles;
+	ffs->epfiles = NULL;
+	spin_unlock_irqrestore(&ffs->eps_lock, flags);
 
-	if (ffs->ffs_eventfd)
+	/*
+	 * potential race possible between ffs_func_eps_disable
+	 * & ffs_epfile_release therefore maintaining a local
+	 * copy of epfile will save us from use-after-free.
+	 */
+	if (epfiles) {
+		ffs_epfiles_destroy(epfiles, ffs->eps_count);
+		ffs->epfiles = NULL;
+	}
+
+	if (ffs->ffs_eventfd) {
 		eventfd_ctx_put(ffs->ffs_eventfd);
+		ffs->ffs_eventfd = NULL;
+	}
 
 	kfree(ffs->raw_descs_data);
 	kfree(ffs->raw_strings);
@@ -1811,7 +1833,6 @@ static void ffs_data_reset(struct ffs_data *ffs)
 
 	ffs_data_clear(ffs);
 
-	ffs->epfiles = NULL;
 	ffs->raw_descs_data = NULL;
 	ffs->raw_descs = NULL;
 	ffs->raw_strings = NULL;
@@ -1940,12 +1961,15 @@ static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count)
 
 static void ffs_func_eps_disable(struct ffs_function *func)
 {
-	struct ffs_ep *ep         = func->eps;
-	struct ffs_epfile *epfile = func->ffs->epfiles;
-	unsigned count            = func->ffs->eps_count;
+	struct ffs_ep *ep;
+	struct ffs_epfile *epfile;
+	unsigned short count;
 	unsigned long flags;
 
 	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	count = func->ffs->eps_count;
+	epfile = func->ffs->epfiles;
+	ep = func->eps;
 	while (count--) {
 		/* pending requests get nuked */
 		if (likely(ep->ep))
@@ -1963,14 +1987,18 @@ static void ffs_func_eps_disable(struct ffs_function *func)
 
 static int ffs_func_eps_enable(struct ffs_function *func)
 {
-	struct ffs_data *ffs      = func->ffs;
-	struct ffs_ep *ep         = func->eps;
-	struct ffs_epfile *epfile = ffs->epfiles;
-	unsigned count            = ffs->eps_count;
+	struct ffs_data *ffs;
+	struct ffs_ep *ep;
+	struct ffs_epfile *epfile;
+	unsigned short count;
 	unsigned long flags;
 	int ret = 0;
 
 	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	ffs = func->ffs;
+	ep = func->eps;
+	epfile = ffs->epfiles;
+	count = ffs->eps_count;
 	while(count--) {
 		ep->ep->driver_data = ep;
 
@@ -2658,6 +2686,7 @@ static int __ffs_data_got_strings(struct ffs_data *ffs,
 
 	do { /* lang_count > 0 so we can use do-while */
 		unsigned needed = needed_count;
+		u32 str_per_lang = str_count;
 
 		if (unlikely(len < 3))
 			goto error_free;
@@ -2693,7 +2722,7 @@ static int __ffs_data_got_strings(struct ffs_data *ffs,
 
 			data += length + 1;
 			len -= length + 1;
-		} while (--str_count);
+		} while (--str_per_lang);
 
 		s->id = 0;   /* terminator */
 		s->s = NULL;
@@ -3049,6 +3078,7 @@ static inline struct f_fs_opts *ffs_do_functionfs_bind(struct usb_function *f,
 	struct ffs_function *func = ffs_func_from_usb(f);
 	struct f_fs_opts *ffs_opts =
 		container_of(f->fi, struct f_fs_opts, func_inst);
+	struct ffs_data *ffs_data;
 	int ret;
 
 	ENTER();
@@ -3063,12 +3093,13 @@ static inline struct f_fs_opts *ffs_do_functionfs_bind(struct usb_function *f,
 	if (!ffs_opts->no_configfs)
 		ffs_dev_lock();
 	ret = ffs_opts->dev->desc_ready ? 0 : -ENODEV;
-	func->ffs = ffs_opts->dev->ffs_data;
+	ffs_data = ffs_opts->dev->ffs_data;
 	if (!ffs_opts->no_configfs)
 		ffs_dev_unlock();
 	if (ret)
 		return ERR_PTR(ret);
 
+	func->ffs = ffs_data;
 	func->conf = c;
 	func->gadget = c->cdev->gadget;
 
@@ -3523,6 +3554,7 @@ static void ffs_free_inst(struct usb_function_instance *f)
 	struct f_fs_opts *opts;
 
 	opts = to_f_fs_opts(f);
+	ffs_release_dev(opts->dev);
 	ffs_dev_lock();
 	_ffs_free_dev(opts->dev);
 	ffs_dev_unlock();
@@ -3584,6 +3616,9 @@ static void ffs_func_unbind(struct usb_configuration *c,
 		ffs->func = NULL;
 	}
 
+	/* Drain any pending AIO completions */
+	drain_workqueue(ffs->io_completion_wq);
+
 	if (!--opts->refcnt)
 		functionfs_unbind(ffs);
 
@@ -3707,47 +3742,48 @@ static void _ffs_free_dev(struct ffs_dev *dev)
 {
 	list_del(&dev->entry);
 
-	/* Clear the private_data pointer to stop incorrect dev access */
-	if (dev->ffs_data)
-		dev->ffs_data->private_data = NULL;
-
 	kfree(dev);
 	if (list_empty(&ffs_devices))
 		functionfs_cleanup();
 }
 
-static void *ffs_acquire_dev(const char *dev_name)
+static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data)
 {
+	int ret = 0;
 	struct ffs_dev *ffs_dev;
 
 	ENTER();
 	ffs_dev_lock();
 
 	ffs_dev = _ffs_find_dev(dev_name);
-	if (!ffs_dev)
-		ffs_dev = ERR_PTR(-ENOENT);
-	else if (ffs_dev->mounted)
-		ffs_dev = ERR_PTR(-EBUSY);
-	else if (ffs_dev->ffs_acquire_dev_callback &&
-	    ffs_dev->ffs_acquire_dev_callback(ffs_dev))
-		ffs_dev = ERR_PTR(-ENOENT);
-	else
+	if (!ffs_dev) {
+		ret = -ENOENT;
+	} else if (ffs_dev->mounted) {
+		ret = -EBUSY;
+	} else if (ffs_dev->ffs_acquire_dev_callback &&
+		   ffs_dev->ffs_acquire_dev_callback(ffs_dev)) {
+		ret = -ENOENT;
+	} else {
 		ffs_dev->mounted = true;
+		ffs_dev->ffs_data = ffs_data;
+		ffs_data->private_data = ffs_dev;
+	}
 
 	ffs_dev_unlock();
-	return ffs_dev;
+	return ret;
 }
 
-static void ffs_release_dev(struct ffs_data *ffs_data)
+static void ffs_release_dev(struct ffs_dev *ffs_dev)
 {
-	struct ffs_dev *ffs_dev;
-
 	ENTER();
 	ffs_dev_lock();
 
-	ffs_dev = ffs_data->private_data;
-	if (ffs_dev) {
+	if (ffs_dev && ffs_dev->mounted) {
 		ffs_dev->mounted = false;
+		if (ffs_dev->ffs_data) {
+			ffs_dev->ffs_data->private_data = NULL;
+			ffs_dev->ffs_data = NULL;
+		}
 
 		if (ffs_dev->ffs_release_dev_callback)
 			ffs_dev->ffs_release_dev_callback(ffs_dev);
@@ -3775,7 +3811,6 @@ static int ffs_ready(struct ffs_data *ffs)
 	}
 
 	ffs_obj->desc_ready = true;
-	ffs_obj->ffs_data = ffs;
 
 	if (ffs_obj->ffs_ready_callback) {
 		ret = ffs_obj->ffs_ready_callback(ffs);
@@ -3803,7 +3838,6 @@ static void ffs_closed(struct ffs_data *ffs)
 		goto done;
 
 	ffs_obj->desc_ready = false;
-	ffs_obj->ffs_data = NULL;
 
 	if (test_and_clear_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags) &&
 	    ffs_obj->ffs_closed_callback)