linux-kernel - [PATCH 3.18 071/150] misc: genwqe: check for error from get_user_pages

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Date:	Tue, 13 Jan 2015 23:22:22 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Ian Abbott <abbotti@....co.uk>
Subject: [PATCH 3.18 071/150] misc: genwqe: check for error from get_user_pages_fast()

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ian Abbott <abbotti@....co.uk>

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@....co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/genwqe/card_utils.c |    2 ++
 1 file changed, 2 insertions(+)

--- 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 *
 				 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) {

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