[PATCH 12/16] mm: validate get_user_pages_fast flags

[Christoph Hellwig]

We can only deal with FOLL_WRITE and/or FOLL_LONGTERM in
get_user_pages_fast, so reject all other flags.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 mm/gup.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index fe4f205651fd..78dc1871b3d4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2317,6 +2317,9 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
 	unsigned long addr, len, end;
 	int nr = 0, ret = 0;
 
+	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM)))
+		return -EINVAL;
+
 	start = untagged_addr(start) & PAGE_MASK;
 	addr = start;
 	len = (unsigned long) nr_pages << PAGE_SHIFT;
-- 
2.20.1