[PATCH 3.18 071/150] misc: genwqe: check for error from get_user_pages_fast()

Greg Kroah-Hartman
2015-01-14T07:27:41Z

From: Ian Abbott <abbotti@mev.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@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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) {