patch "usb: gadget: f_fs: Use local copy of descriptors for userspace copy" added to usb-linus

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

usb: gadget: f_fs: Use local copy of descriptors for userspace copy

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 a4b98a7512f18534ce33a7e98e49115af59ffa00 Mon Sep 17 00:00:00 2001
From: Vamsi Krishna Samavedam <[email protected]>
Date: Mon, 30 Nov 2020 12:34:53 -0800
Subject: usb: gadget: f_fs: Use local copy of descriptors for userspace copy

The function may be unbound causing the ffs_ep and its descriptors to be freed while userspace is in the middle of an ioctl requesting the same descriptors. Avoid dangling pointer reference by first making a local copy of desctiptors before releasing the spinlock.

---
 drivers/usb/gadget/function/f_fs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index 046f770a76da..c727cb5de871 100644
@@ -1324,7 +1324,7 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
 	case FUNCTIONFS_ENDPOINT_DESC:
 	{
 		int desc_idx;
-		struct usb_endpoint_descriptor *desc;
+		struct usb_endpoint_descriptor desc1, *desc;
 
 		switch (epfile->ffs->gadget->speed) {
 		case USB_SPEED_SUPER:

@@ -1336,10 +1336,12 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
 		default:
 			desc_idx = 0;
 		}
+
 		desc = epfile->ep->descs[desc_idx];
+		memcpy(&desc1, desc, desc->bLength);
 
 		spin_unlock_irq(&epfile->ffs->eps_lock);
-		ret = copy_to_user((void __user *)value, desc, desc->bLength);
+		ret = copy_to_user((void __user *)value, &desc1, desc1.bLength);
 		if (ret)
 			ret = -EFAULT;
 		return ret;

2.29.2