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

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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@xxxxxxxxxx>
---
 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




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