linux-kernel - [PATCH] misc: genwqe: check for error from get_user_pages

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Message-Id: <1415291019-6178-1-git-send-email-abbotti@mev.co.uk>
Date:	Thu,  6 Nov 2014 16:23:39 +0000
From:	Ian Abbott <abbotti@....co.uk>
To:	Frank Haverkamp <haver@...ux.vnet.ibm.com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	<linux-kernel@...r.kernel.org>, Ian Abbott <abbotti@....co.uk>,
	<stable@...r.kernel.org>
Subject: [PATCH] misc: genwqe: check for error from get_user_pages_fast()

`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@....co.uk>
Cc: <stable@...r.kernel.org> # 3.14.x # 3.15.x # 3.16.x # 3.17.x
---
 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 7cb3b7e..1ca94e6 100644
--- a/drivers/misc/genwqe/card_utils.c
+++ b/drivers/misc/genwqe/card_utils.c
@@ -590,6 +590,8 @@ 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) {
-- 
2.1.1

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