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From:   Kees Cook <keescook@chromium.org>
Date:   Thu, 7 Jun 2018 13:43:08 -0700
Message-ID: <CAGXu5j+X1BrPhtdOP9AJ-oSovoHcS1CQHNsiFisdQt=Th7LgWw@mail.gmail.com>
Subject: Re: [PATCH 1/6] Convert virtio_console to struct_size
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Matthew Wilcox <mawilcox@microsoft.com>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>
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On Thu, Jun 7, 2018 at 12:29 PM, Kees Cook <keescook@chromium.org> wrote:
> On Thu, Jun 7, 2018 at 7:57 AM, Matthew Wilcox <willy@infradead.org> wrote:
>> From: Matthew Wilcox <mawilcox@microsoft.com>
>>
>> Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
>> ---
>>  drivers/char/virtio_console.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
>> index 21085515814f..4bf7c06c2343 100644
>> --- a/drivers/char/virtio_console.c
>> +++ b/drivers/char/virtio_console.c
>> @@ -433,8 +433,7 @@ static struct port_buffer *alloc_buf(struct virtio_device *vdev, size_t buf_size
>>          * Allocate buffer and the sg list. The sg list array is allocated
>>          * directly after the port_buffer struct.
>>          */
>> -       buf = kmalloc(sizeof(*buf) + sizeof(struct scatterlist) * pages,
>> -                     GFP_KERNEL);
>> +       buf = kmalloc(struct_size(buf, sg, pages), GFP_KERNEL);
>>         if (!buf)
>>                 goto fail;
>
> I feel like this one should have been caught by Coccinelle... maybe
> the transitive case got missed? Regardless, I'll figure out how to
> improve the script and/or take these.

Oh, duh. Got it: "struct scatterlist" is not an expression, it's a
type. I'll adjust the script, catch stragglers, and incorporate your
patches. :)

Thanks!

-Kees

-- 
Kees Cook
Pixel Security