[PATCH] mm/gup_benchmark: prevent integer overflow in ioctl

Dan Carpenter
2018-10-25T06:15:46Z

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.

Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() benchmarking")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
mm/gup_benchmark.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index debf11388a60..5b42d3d4b60a 100644
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -27,6 +27,9 @@ 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)
--
2.11.0