2023-09-22 20:36:58

by Kees Cook

Subject: [PATCH] virtio_console: Annotate struct port_buffer with __counted_by

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 checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct port_buffer.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Amit Shah <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
drivers/char/virtio_console.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 680d1ef2a217..431e9e5bf9c1 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -106,7 +106,7 @@ struct port_buffer {
unsigned int sgpages;

/* sg is used if spages > 0. sg must be the last in is struct */
- struct scatterlist sg[];
+ struct scatterlist sg[] __counted_by(sgpages);
};

/*
--
2.34.1

2023-09-23 17:44:31

by Gustavo A. R. Silva

Subject: Re: [PATCH] virtio_console: Annotate struct port_buffer with __counted_by

On 9/22/23 11:51, Kees Cook 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 checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct port_buffer.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Amit Shah <[email protected]>
> Cc: Arnd Bergmann <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>

Reviewed-by: Gustavo A. R. Silva <[email protected]>

Thanks
--
Gustavo

> ---
> drivers/char/virtio_console.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 680d1ef2a217..431e9e5bf9c1 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -106,7 +106,7 @@ struct port_buffer {
> unsigned int sgpages;
>
> /* sg is used if spages > 0. sg must be the last in is struct */
> - struct scatterlist sg[];
> + struct scatterlist sg[] __counted_by(sgpages);
> };
>
> /*

2023-09-25 15:37:25

by Amit Shah

Subject: Re: [PATCH] virtio_console: Annotate struct port_buffer with __counted_by

On Fri, 2023-09-22 at 10:51 -0700, Kees Cook 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 checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct port_buffer.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Amit Shah <[email protected]>
> Cc: Arnd Bergmann <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> drivers/char/virtio_console.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 680d1ef2a217..431e9e5bf9c1 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -106,7 +106,7 @@ struct port_buffer {
> unsigned int sgpages;
>
> /* sg is used if spages > 0. sg must be the last in is struct */
> - struct scatterlist sg[];
> + struct scatterlist sg[] __counted_by(sgpages);
> };

Reviewed-by: Amit Shah <[email protected]>

Greg, please pick this up.

Thanks,

Amit

2023-10-24 21:19:41

by Kees Cook

Subject: Re: [PATCH] virtio_console: Annotate struct port_buffer with __counted_by

On Fri, 22 Sep 2023 10:51:15 -0700, Kees Cook 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 checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct port_buffer.
>
> [...]

Applied to for-next/hardening, thanks!

[1/1] virtio_console: Annotate struct port_buffer with __counted_by
https://git.kernel.org/kees/c/bf5abc17bc43

Take care,

--
Kees Cook