Re: [PATCH] mtd: rawnand: rockchip: Use struct_size()

[Gustavo A. R. Silva]

On 10/1/23 09:44, Christophe JAILLET wrote:
> Use struct_size() instead of hand writing it.
> This is less verbose and more robust.
>
> While at it, 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).

Again, I'd prefer this as two separate patches.

> Also remove a useless comment about the position of a flex-array in a
> structure.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>

In any case:

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

Thanks
--
Gustavo

> ---
> This patch is part of a work done in parallel of what is currently worked
> on by Kees Cook.
>
> My patches are only related to corner cases that do NOT match the
> semantic of his Coccinelle script[1].
>
> In this case, struct_size() was not used to compute the size needed for the
> structure and its flex array.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> ---
>   drivers/mtd/nand/raw/rockchip-nand-controller.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mtd/nand/raw/rockchip-nand-controller.c b/drivers/mtd/nand/raw/rockchip-nand-controller.c
> index 5bc90ffa721f..596cf9a78274 100644
> --- a/drivers/mtd/nand/raw/rockchip-nand-controller.c
> +++ b/drivers/mtd/nand/raw/rockchip-nand-controller.c
> @@ -158,8 +158,7 @@ struct rk_nfc_nand_chip {
>   	u32 timing;
>   
>   	u8 nsels;
> -	u8 sels[];
> -	/* Nothing after this field. */
> +	u8 sels[] __counted_by(nsels);
>   };
>   
>   struct rk_nfc {
> @@ -1119,7 +1118,7 @@ static int rk_nfc_nand_chip_init(struct device *dev, struct rk_nfc *nfc,
>   		return -EINVAL;
>   	}
>   
> -	rknand = devm_kzalloc(dev, sizeof(*rknand) + nsels * sizeof(u8),
> +	rknand = devm_kzalloc(dev, struct_size(rknand, sels, nsels),
>   			      GFP_KERNEL);
>   	if (!rknand)
>   		return -ENOMEM;