linux-kernel - Re: [PATCH v2 06/24] dma-buf: system_heap: use vmalloc

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Message-ID: <CANDhNCrPHJjDwGLMY_p8Z21bCnBvTzQmztYqRykTBD9t-+mbcQ@mail.gmail.com>
Date:   Tue, 27 Jun 2023 11:52:27 -0700
From:   John Stultz <jstultz@...gle.com>
To:     Julia Lawall <Julia.Lawall@...ia.fr>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        kernel-janitors@...r.kernel.org, keescook@...omium.org,
        christophe.jaillet@...adoo.fr, kuba@...nel.org,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Liam Mark <lmark@...eaurora.org>,
        Laura Abbott <labbott@...hat.com>,
        Brian Starkey <Brian.Starkey@....com>,
        Christian König <christian.koenig@....com>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/24] dma-buf: system_heap: use vmalloc_array and vcalloc

On Tue, Jun 27, 2023 at 7:44 AM Julia Lawall <Julia.Lawall@...ia.fr> wrote:
>
> Use vmalloc_array and vcalloc to protect against
> multiplication overflows.
>
> The changes were done using the following Coccinelle
> semantic patch:
>
> // <smpl>
> @initialize:ocaml@
> @@
>
> let rename alloc =
>   match alloc with
>     "vmalloc" -> "vmalloc_array"
>   | "vzalloc" -> "vcalloc"
>   | _ -> failwith "unknown"
>
> @@
>     size_t e1,e2;
>     constant C1, C2;
>     expression E1, E2, COUNT, x1, x2, x3;
>     typedef u8;
>     typedef __u8;
>     type t = {u8,__u8,char,unsigned char};
>     identifier alloc = {vmalloc,vzalloc};
>     fresh identifier realloc = script:ocaml(alloc) { rename alloc };
> @@
>
> (
>       alloc(x1*x2*x3)
> |
>       alloc(C1 * C2)
> |
>       alloc((sizeof(t)) * (COUNT), ...)
> |
> -     alloc((e1) * (e2))
> +     realloc(e1, e2)
> |
> -     alloc((e1) * (COUNT))
> +     realloc(COUNT, e1)
> |
> -     alloc((E1) * (E2))
> +     realloc(E1, E2)
> )
> // </smpl>
>
> Signed-off-by: Julia Lawall <Julia.Lawall@...ia.fr>
>
> ---
> v2: Use vmalloc_array and vcalloc instead of array_size.
> This also leaves a multiplication of a constant by a sizeof
> as is.  Two patches are thus dropped from the series.
>
>  drivers/dma-buf/heaps/system_heap.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff -u -p a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -221,7 +221,7 @@ static void *system_heap_do_vmap(struct
>  {
>         struct sg_table *table = &buffer->sg_table;
>         int npages = PAGE_ALIGN(buffer->len) / PAGE_SIZE;
> -       struct page **pages = vmalloc(sizeof(struct page *) * npages);
> +       struct page **pages = vmalloc_array(npages, sizeof(struct page *));
>         struct page **tmp = pages;
>         struct sg_page_iter piter;
>         void *vaddr;

Seems reasonable. Thanks for sending this out!

Acked-by: John Stultz <jstultz@...gle.com>

thanks
-john