[3.13.y-ckt stable] Patch "gadgetfs: use-after-free in ->aio_read()" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    gadgetfs: use-after-free in ->aio_read()

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt19.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 29e97f7298ed490b12f6c27e60b0607b4f06f081 Mon Sep 17 00:00:00 2001
From: Al Viro <viro at zeniv.linux.org.uk>
Date: Fri, 6 Feb 2015 02:07:45 -0500
Subject: gadgetfs: use-after-free in ->aio_read()

commit f01d35a15fa04162a58b95970fc01fa70ec9dacd upstream.

AIO_PREAD requests call ->aio_read() with iovec on caller's stack, so if
we are going to access it asynchronously, we'd better get ourselves
a copy - the one on kernel stack of aio_run_iocb() won't be there
anymore.  function/f_fs.c take care of doing that, legacy/inode.c
doesn't...

Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/gadget/inode.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index b94c049..ff3e6e6 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -568,7 +568,6 @@ static ssize_t ep_copy_to_user(struct kiocb_priv *priv)
 		if (total == 0)
 			break;
 	}
-
 	return len;
 }

@@ -587,6 +586,7 @@ static void ep_user_copy_worker(struct work_struct *work)
 	aio_complete(iocb, ret, ret);

 	kfree(priv->buf);
+	kfree(priv->iv);
 	kfree(priv);
 }

@@ -607,6 +607,7 @@ static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
 	 */
 	if (priv->iv == NULL || unlikely(req->actual == 0)) {
 		kfree(req->buf);
+		kfree(priv->iv);
 		kfree(priv);
 		iocb->private = NULL;
 		/* aio_complete() reports bytes-transferred _and_ faults */
@@ -642,7 +643,7 @@ ep_aio_rwtail(
 	struct usb_request	*req;
 	ssize_t			value;

-	priv = kmalloc(sizeof *priv, GFP_KERNEL);
+	priv = kzalloc(sizeof *priv, GFP_KERNEL);
 	if (!priv) {
 		value = -ENOMEM;
 fail:
@@ -651,7 +652,14 @@ fail:
 	}
 	iocb->private = priv;
 	priv->iocb = iocb;
-	priv->iv = iv;
+	if (iv) {
+		priv->iv = kmemdup(iv, nr_segs * sizeof(struct iovec),
+				   GFP_KERNEL);
+		if (!priv->iv) {
+			kfree(priv);
+			goto fail;
+		}
+	}
 	priv->nr_segs = nr_segs;
 	INIT_WORK(&priv->work, ep_user_copy_worker);

@@ -691,6 +699,7 @@ fail:
 	mutex_unlock(&epdata->lock);

 	if (unlikely(value)) {
+		kfree(priv->iv);
 		kfree(priv);
 		put_ep(epdata);
 	} else
--
1.9.1