2023-10-09 21:31:27

by Gustavo A. R. Silva

Subject: [PATCH][next] soc: qcom: apr: Add __counted_by for struct apr_rx_buf and use struct_size()

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 <[email protected]>
---
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

2023-10-09 22:05:08

by Kees Cook

Subject: Re: [PATCH][next] soc: qcom: apr: Add __counted_by for struct apr_rx_buf and use struct_size()

On Mon, Oct 09, 2023 at 03:30:17PM -0600, Gustavo A. R. Silva 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 <[email protected]>

Yup, looks right.

Reviewed-by: Kees Cook <[email protected]>

--
Kees Cook

2023-10-09 23:47:03

by Justin Stitt

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
<[email protected]> 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 <[email protected]>

Excited for __counted_by to land! This looks right.

Reviewed-by: Justin Stitt <[email protected]>

> ---
> 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
>
>

2023-10-16 18:56:40

by Bjorn Andersson

Subject: Re: [PATCH][next] soc: qcom: apr: Add __counted_by for struct apr_rx_buf and use struct_size()

On Mon, Oct 09, 2023 at 03:30:17PM -0600, Gustavo A. R. Silva 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 <[email protected]>

Applied, thanks.

> ---
> 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
>