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 io_mapped_ubuf.

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

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: io-uring@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 io_uring/rsrc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 8afa9ec66a55..8625181fb87a 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -54,7 +54,7 @@ struct io_mapped_ubuf {
 	u64		ubuf_end;
 	unsigned int	nr_bvecs;
 	unsigned long	acct_pages;
-	struct bio_vec	bvec[];
+	struct bio_vec	bvec[] __counted_by(nr_bvecs);
 };
 
 void io_rsrc_node_ref_zero(struct io_rsrc_node *node);
-- 
2.34.1

On Thu, 17 Aug 2023 14:21:47 -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 io_mapped_ubuf.
> 
> [...]

Applied, thanks!

[1/1] io_uring/rsrc: Annotate struct io_mapped_ubuf with __counted_by
      commit: 04d9244c9420db33149608a566399176d57690f8

Best regards,
-- 
Jens Axboe

On 8/17/23 15:21, 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 io_mapped_ubuf.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Pavel Begunkov <asml.silence@gmail.com>
> Cc: io-uring@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
>   io_uring/rsrc.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> index 8afa9ec66a55..8625181fb87a 100644
> --- a/io_uring/rsrc.h
> +++ b/io_uring/rsrc.h
> @@ -54,7 +54,7 @@ struct io_mapped_ubuf {
>   	u64		ubuf_end;
>   	unsigned int	nr_bvecs;
>   	unsigned long	acct_pages;
> -	struct bio_vec	bvec[];
> +	struct bio_vec	bvec[] __counted_by(nr_bvecs);
>   };
>   
>   void io_rsrc_node_ref_zero(struct io_rsrc_node *node);