mm/mlock.c: change count_mm_mlocked_page_nr return type

[ Upstream commit 0874bb49bb21bf24deda853e8bf61b8325e24bcb ]

On a 64-bit machine the value of "vma->vm_end - vma->vm_start" may be
negative when using 32 bit ints and the "count >> PAGE_SHIFT"'s result
will be wrong.  So change the local variable and return value to
unsigned long to fix the problem.

Link: http://lkml.kernel.org/r/20190513023701.83056-1-swkhack@gmail.com
Fixes: 0cf2f6f6dc60 ("mm: mlock: check against vma for actual mlock() size")
Signed-off-by: swkhack <swkhack@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/mm/mlock.c b/mm/mlock.c
index f0505692a5f428b958242d745ceb394dcda8509e..3e7fe404bfb894f0ea0fbebe3bccc877a976cacc 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -630,11 +630,11 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
  * is also counted.
  * Return value: previously mlocked page counts
  */
-static int count_mm_mlocked_page_nr(struct mm_struct *mm,
+static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
                unsigned long start, size_t len)
 {
        struct vm_area_struct *vma;
-       int count = 0;
+       unsigned long count = 0;
 
        if (mm == NULL)
                mm = current->mm;