mm/gup_benchmark.c: prevent integer overflow in ioctl

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@kili.mountain
Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() benchmarking")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index debf11388a600d0f445ed1ac055e14bf0d55790d..5b42d3d4b60aa3a921002abf8f2872bc6e0764f8 100644 (file)
--- 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)