misc: mic: scif: Fix error handling path

Inside __scif_pin_pages(), when map_flags != SCIF_MAP_KERNEL it
will call pin_user_pages_fast() to map nr_pages. However,
pin_user_pages_fast() might fail with a return value -ERRNO.

The return value is stored in pinned_pages->nr_pages. which in
turn is passed to unpin_user_pages(), which expects
pinned_pages->nr_pages >=0, else disaster.

Fix this by assigning pinned_pages->nr_pages to 0 if
pin_user_pages_fast() returns -ERRNO.

Fixes: ba612aa8b487 ("misc: mic: SCIF memory registration and unregistration")
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Link: https://lore.kernel.org/r/1600570295-29546-1-git-send-email-jrdr.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
index 2da3b47..18fb9d8 100644 (file)
--- a/drivers/misc/mic/scif/scif_rma.c
+++ b/drivers/misc/mic/scif/scif_rma.c
@@ -1392,6 +1392,8 @@ retry:
                                (prot & SCIF_PROT_WRITE) ? FOLL_WRITE : 0,
                                pinned_pages->pages);
                if (nr_pages != pinned_pages->nr_pages) {
+                       if (pinned_pages->nr_pages < 0)
+                               pinned_pages->nr_pages = 0;
                        if (try_upgrade) {
                                if (ulimit)
                                        __scif_dec_pinned_vm_lock(mm, nr_pages);
@@ -1408,7 +1410,6 @@ retry:
 
        if (pinned_pages->nr_pages < nr_pages) {
                err = -EFAULT;
-               pinned_pages->nr_pages = nr_pages;
                goto dec_pinned;
        }
 
@@ -1421,7 +1422,6 @@ dec_pinned:
                __scif_dec_pinned_vm_lock(mm, nr_pages);
        /* Something went wrong! Rollback */
 error_unmap:
-       pinned_pages->nr_pages = nr_pages;
        scif_destroy_pinned_pages(pinned_pages);
        *pages = NULL;
        dev_dbg(scif_info.mdev.this_device,