Patch "usb: gadget: f_fs: Fix EFAULT generation for async read operations" has been added to the 4.6-stable tree

[<gregkh@linuxfoundation.org>]

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

    usb: gadget: f_fs: Fix EFAULT generation for async read operations

to the 4.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-gadget-f_fs-fix-efault-generation-for-async-read-operations.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 332a5b446b7916d272c2a659a3b20909ce34d2c1 Mon Sep 17 00:00:00 2001
From: Lars-Peter Clausen <lars@metafoo.de>
Date: Wed, 30 Mar 2016 13:49:14 +0200
Subject: usb: gadget: f_fs: Fix EFAULT generation for async read operations

From: Lars-Peter Clausen <lars@metafoo.de>

commit 332a5b446b7916d272c2a659a3b20909ce34d2c1 upstream.

In the current implementation functionfs generates a EFAULT for async read
operations if the read buffer size is larger than the URB data size. Since
a application does not necessarily know how much data the host side is
going to send it typically supplies a buffer larger than the actual data,
which will then result in a EFAULT error.

This behaviour was introduced while refactoring the code to use iov_iter
interface in commit c993c39b8639 ("gadget/function/f_fs.c: use put iov_iter
into io_data"). The original code took the minimum over the URB size and
the user buffer size and then attempted to copy that many bytes using
copy_to_user(). If copy_to_user() could not copy all data a EFAULT error
was generated. Restore the original behaviour by only generating a EFAULT
error when the number of bytes copied is not the size of the URB and the
target buffer has not been fully filled.

Commit 342f39a6c8d3 ("usb: gadget: f_fs: fix check in read operation")
already fixed the same problem for the synchronous read path.

Fixes: c993c39b8639 ("gadget/function/f_fs.c: use put iov_iter into io_data")
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/gadget/function/f_fs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -651,7 +651,7 @@ static void ffs_user_copy_worker(struct
 	if (io_data->read && ret > 0) {
 		use_mm(io_data->mm);
 		ret = copy_to_iter(io_data->buf, ret, &io_data->data);
-		if (iov_iter_count(&io_data->data))
+		if (ret != io_data->req->actual && iov_iter_count(&io_data->data))
 			ret = -EFAULT;
 		unuse_mm(io_data->mm);
 	}


Patches currently in stable-queue which might be from lars@metafoo.de are

queue-4.6/usb-gadget-f_fs-fix-efault-generation-for-async-read-operations.patch