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@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/drivers/misc/genwqe/card_utils.c b/drivers/misc/genwqe/card_utils.c
index 62cc6bb3f62e27bc30e03636886acf371d0e5b06..ded1c2507d3d55154e16642b8396a1dd623831c3 100644 (file)
--- 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) {