[3.16.y-ckt stable] Patch "misc: genwqe: check for error from get_user_pages_fast()" has been added to staging queue

[Luis Henriques]

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

    misc: genwqe: check for error from get_user_pages_fast()

to the linux-3.16.y-queue branch of the 3.16.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-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt4.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From eb6719481dd5febd5b04061472ad21028e05e2e4 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Thu, 6 Nov 2014 16:23:39 +0000
Subject: misc: genwqe: check for error from get_user_pages_fast()

commit cf35d6e0475982667b0d2d318fb27be4b8849827 upstream.

`genwqe_user_vmap()` calls `get_user_pages_fast()` and if the return
value is less than the number of pages requested, it frees the pages and
returns an error (`-EFAULT`).  However, it fails to consider a negative
error return value from `get_user_pages_fast()`.  In that case, the test
`if (rc < m->nr_pages)` will be false (due to promotion of `rc` to a
large `unsigned int`) and the code will continue on to call
`genwqe_map_pages()` with an invalid list of page pointers.  Fix it by
bailing out if `get_user_pages_fast()` returns a negative error value.

Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/misc/genwqe/card_utils.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/misc/genwqe/card_utils.c b/drivers/misc/genwqe/card_utils.c
index 62cc6bb3f62e..ded1c2507d3d 100644
--- a/drivers/misc/genwqe/card_utils.c
+++ b/drivers/misc/genwqe/card_utils.c
@@ -580,6 +580,8 @@ int genwqe_user_vmap(struct genwqe_dev *cd, struct dma_mapping *m, void *uaddr,
 				 m->nr_pages,
 				 1,		/* write by caller */
 				 m->page_list);	/* ptrs to pages */
+	if (rc < 0)
+		goto fail_get_user_pages;

 	/* assumption: get_user_pages can be killed by signals. */
 	if (rc < m->nr_pages) {
--
2.1.4