linux-hardening - Re: [PATCH] mtd: rawnand: rockchip: Use struct

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Message-ID: <1bcde585-f740-8959-6e2e-19793795b60e@embeddedor.com>
Date: Sun, 1 Oct 2023 09:49:16 +0200
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 Heiko Stuebner <heiko@...ech.de>, Kees Cook <keescook@...omium.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>
Cc: linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 linux-mtd@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-hardening@...r.kernel.org,
 llvm@...ts.linux.dev
Subject: Re: [PATCH] mtd: rawnand: rockchip: Use struct_size()

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@...adoo.fr>

In any case:

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

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;