[PATCH AUTOSEL 4.19 18/44] mm/gup_benchmark.c: prevent integer overflow in ioctl

[Sasha Levin]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit 4b408c74ee5a0b74fc9265c2fe39b0e7dec7c056 ]

The concern here is that "gup->size" is a u64 and "nr_pages" is unsigned
long.  On 32 bit systems we could trick the kernel into allocating fewer
pages than expected.

Link: http://lkml.kernel.org/r/20181025061546.hnhkv33diogf2uis@xxxxxxxxxxxxx
Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() benchmarking")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: YueHaibing <yuehaibing@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/gup_benchmark.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index 7405c9d89d65..7e6f2d2dafb5 100644
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -23,6 +23,9 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 	int nr;
 	struct page **pages;
 
+	if (gup->size > ULONG_MAX)
+		return -EINVAL;
+
 	nr_pages = gup->size / PAGE_SIZE;
 	pages = kvcalloc(nr_pages, sizeof(void *), GFP_KERNEL);
 	if (!pages)
-- 
2.17.1