linux-hardening - Re: [PATCH][next] soc: qcom: apr: Add __counted_by for struct apr_rx_buf and use struct

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Date: Mon, 9 Oct 2023 16:46:36 -0700
From: Justin Stitt <justinstitt@...gle.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>, Banajit Goswami <bgoswami@...cinc.com>, 
	Andy Gross <agross@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, alsa-devel@...a-project.org, 
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] soc: qcom: apr: Add __counted_by for struct
 apr_rx_buf and use struct_size()

On Mon, Oct 9, 2023 at 2:30 PM Gustavo A. R. Silva
<gustavoars@...nel.org> wrote:
>
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> While there, use struct_size() helper, instead of the open-coded
> version, to calculate the size for the allocation of the whole
> flexible structure, including of course, the flexible-array member.
>
> This code was found with the help of Coccinelle, and audited and
> fixed manually.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Excited for __counted_by to land! This looks right.

Reviewed-by: Justin Stitt <justinstitt@...gle.com>

> ---
>  drivers/soc/qcom/apr.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/soc/qcom/apr.c b/drivers/soc/qcom/apr.c
> index 30f81d6d9d9d..1f8b315576a4 100644
> --- a/drivers/soc/qcom/apr.c
> +++ b/drivers/soc/qcom/apr.c
> @@ -41,7 +41,7 @@ struct packet_router {
>  struct apr_rx_buf {
>         struct list_head node;
>         int len;
> -       uint8_t buf[];
> +       uint8_t buf[] __counted_by(len);
>  };
>
>  /**
> @@ -171,7 +171,7 @@ static int apr_callback(struct rpmsg_device *rpdev, void *buf,
>                 return -EINVAL;
>         }
>
> -       abuf = kzalloc(sizeof(*abuf) + len, GFP_ATOMIC);
> +       abuf = kzalloc(struct_size(abuf, buf, len), GFP_ATOMIC);
>         if (!abuf)
>                 return -ENOMEM;
>
> --
> 2.34.1
>
>