patch "usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()" added to usb-linus

This is a note to let you know that I've just added the patch titled

    usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 0698f0209d8032e8869525aeb68f65ee7fde12ad Mon Sep 17 00:00:00 2001
From: Linyu Yuan <[email protected]>
Date: Fri, 10 Jun 2022 20:17:58 +0800
Subject: usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

In ffs_epfile_io(), when read/write data in blocking mode, it will wait the completion in interruptible mode, if task receive a signal, it will terminate the wait, at same time, if function unbind occurs, ffs_func_unbind() will kfree all eps, ffs_epfile_io() still try to dequeue request by dereferencing ep which may become invalid.

Fix it by add ep spinlock and will not dereference ep if it is not valid.

---
 drivers/usb/gadget/function/f_fs.c | 6 ++++++
 1 file changed, 6 insertions(+)

index e1fcd8bc80a1..e0fa4b186ec6 100644
@@ -1080,6 +1080,11 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 		spin_unlock_irq(&epfile->ffs->eps_lock);
 
 		if (wait_for_completion_interruptible(&io_data->done)) {
+			spin_lock_irq(&epfile->ffs->eps_lock);
+			if (epfile->ep != ep) {
+				ret = -ESHUTDOWN;
+				goto error_lock;
+			}
 			/*
 			 * To avoid race condition with ffs_epfile_io_complete,
 			 * dequeue the request first then check

@@ -1087,6 +1092,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 			 * condition with req->complete callback.
 			 */
 			usb_ep_dequeue(ep->ep, req);
+			spin_unlock_irq(&epfile->ffs->eps_lock);
 			wait_for_completion(&io_data->done);
 			interrupted = io_data->status < 0;
 		}

2.36.1