linux-kernel - Re: integer overflows in kernel/relay.c

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Message-ID: <CAOJsxLGMOfzgHYKrgo42sB26PQw9YZR8TGTbpkeWNZpY4FPOTg@mail.gmail.com>
Date:	Thu, 9 Feb 2012 14:56:42 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jens Axboe <axboe@...nel.dk>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: integer overflows in kernel/relay.c

On Thu, Feb 9, 2012 at 12:25 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Wed, 08 Feb 2012 09:34:16 +0100
> Jens Axboe <axboe@...nel.dk> wrote:
>
>> On 02/07/2012 03:11 PM, Dan Carpenter wrote:
>> > My static checker is warning about integer overflows in kernel/relay.c
>> >
>> > relay_create_buf()
>> >    170
>> >    171          buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
>> >                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> > This can only overflow on 32bit systems.
>>
>> Correct
>
> This is a relatively common problem.  Converting a kzalloc() call to
> kcalloc() fixes it.  But we do not have a non-zeroing version of
> kcalloc().
>
> Please, someone complete this patch and send it to me!
>
>
> --- a/include/linux/slab.h~a
> +++ a/include/linux/slab.h
> @@ -240,11 +240,16 @@ size_t ksize(const void *);
>  * for general use, and so are not documented here. For a full list of
>  * potential flags, always refer to linux/gfp.h.
>  */
> -static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
> +static inline void *wtf_do_i_call_this(size_t n, size_t size, gfp_t flags)

I'd call it kmalloc_array().

>  {
>        if (size != 0 && n > ULONG_MAX / size)
>                return NULL;
> -       return __kmalloc(n * size, flags | __GFP_ZERO);
> +       return __kmalloc(n * size, flags);
> +}
--
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