mm: gup: pass a pointer to virt_to_page()

Functions that work on a pointer to virtual memory such as virt_to_pfn()
and users of that function such as virt_to_page() are supposed to pass a
pointer to virtual memory, ideally a (void *) or other pointer.  However
since many architectures implement virt_to_pfn() as a macro, this function
becomes polymorphic and accepts both a (unsigned long) and a (void *).

If we instead implement a proper virt_to_pfn(void *addr) function the
following happens (occurred on arch/arm):

  mm/gup.c: In function '__get_user_pages_locked':
  mm/gup.c:1599:49: warning: passing argument 1 of 'virt_to_pfn'
    makes pointer from integer without a cast [-Wint-conversion]
    pages[i] = virt_to_page(start);

Fix this with an explicit cast.

Link: https://lkml.kernel.org/r/20220630084124.691207-5-linus.walleij@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index ecf3626882686f001f62792fb297d2d57726aff4..364b274a10c23eb51c77629a9415c83cf22910d9 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1704,7 +1704,7 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
                        goto finish_or_fault;
 
                if (pages) {
-                       pages[i] = virt_to_page(start);
+                       pages[i] = virt_to_page((void *)start);
                        if (pages[i])
                                get_page(pages[i]);
                }