As for FOLL_LONGTERM, it is checked in the slow path
__gup_longterm_unlocked(). But it is not checked in the fast path, which
means a possible leak of CMA page to longterm pinned requirement through
this crack.
Place a check in the fast path.
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/gup.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index f173fcb..0e59af9 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2196,6 +2196,26 @@ static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
return ret;
}
+#ifdef CONFIG_CMA
+static inline int reject_cma_pages(int nr_pinned, struct page **pages)
+{
+ int i;
+
+ for (i = 0; i < nr_pinned; i++)
+ if (is_migrate_cma_page(pages[i])) {
+ put_user_pages(pages + i, nr_pinned - i);
+ return i;
+ }
+
+ return nr_pinned;
+}
+#else
+static inline int reject_cma_pages(int nr_pinned, struct page **pages)
+{
+ return nr_pinned;
+}
+#endif
+
/**
* get_user_pages_fast() - pin user pages in memory
* @start: starting user address
@@ -2236,6 +2256,9 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
ret = nr;
}
+ if (unlikely(gup_flags & FOLL_LONGTERM) && nr)
+ nr = reject_cma_pages(nr, pages);
+
if (nr < nr_pages) {
/* Try to get the remaining pages with get_user_pages */
start += nr << PAGE_SHIFT;
--
2.7.5
