linux-kernel - Re: [PATCH 3/3] coccinelle: catch krealloc() on devm

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Date:	Tue, 16 Feb 2016 18:19:52 +0100 (CET)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Yann Droneaud <ydroneaud@...eya.com>
cc:	Julia Lawall <Julia.Lawall@...6.fr>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Michal Marek <mmarek@...e.com>, Tejun Heo <tj@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 3/3] coccinelle: catch krealloc() on devm_*() allocated
 memory



On Tue, 16 Feb 2016, Yann Droneaud wrote:

> krealloc() must not be used against devm_*() allocated
> memory regions:
>
> - if a bigger memory is to be allocated, krealloc() and
>   __krealloc() could return a different pointer than the
>   one given to them, creating a memory region which is not
>   managed, thus it will not be automatically released on
>   device removal.
>
> - if a bigger memory is to be allocated, krealloc() could
>   kfree() the managed memory region which is passed to it.
>   The old pointer is left registered as a resource for the
>   device. On device removal, this dangling pointer will be
>   used and an unrelated memory region could be released.
>
> - if the requested size is equal to 0, krealloc() can also
>   just behave like kfree(). Here too, the old pointer is
>   kept associated with the device. On device removal, this
>   invalid pointer will be used and an unrelated memory
>   region could be released.
>
> For all these reasons, krealloc() must not be used on a
> pointer returned by devm_*() functions.
>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Pekka Enberg <penberg@...helsinki.fi>
> Signed-off-by: Yann Droneaud <ydroneaud@...eya.com>

Acked-by: Julia Lawall <julia.lawall@...6.fr>

> ---
>  scripts/coccinelle/free/devm_free.cocci | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/scripts/coccinelle/free/devm_free.cocci b/scripts/coccinelle/free/devm_free.cocci
> index 3794cd97494b..c990d2c7ee16 100644
> --- a/scripts/coccinelle/free/devm_free.cocci
> +++ b/scripts/coccinelle/free/devm_free.cocci
> @@ -66,6 +66,10 @@ position p;
>  |
>  * kzfree@p(x)
>  |
> +* __krealloc@p(x, ...)
> +|
> +* krealloc@p(x, ...)
> +|
>  * free_pages@p(x, ...)
>  |
>  * free_page@p(x)
> --
> 2.5.0
>
>