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Date:   Thu, 17 Sep 2020 18:30:01 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Evgeny Novikov <novikov@ispras.ru>
Cc:     Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Stephen Boyd <swboyd@chromium.org>,
        linux-mtd@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        ldv-project@linuxtesting.org
Subject: Re: [PATCH] mtd: rawnand: mtk: avoid underflow in
 mtk_nfc_nand_chip_init()
Message-ID: <20200917183001.393245e8@xps13>
In-Reply-To: <20200916194045.6378-1-novikov@ispras.ru>
References: <20200916194045.6378-1-novikov@ispras.ru>
Organization: Bootlin
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Hi Evgeny,

Evgeny Novikov <novikov@ispras.ru> wrote on Wed, 16 Sep 2020 22:40:45
+0300:

> If of_get_property() will set nsels to negative values the driver may

Is this really a possible case?

Looking at the OF code, I don't think it can ever happen...

> allocate insufficient memory for chip. Moreover, there may be underflow
> for devm_kzalloc(). This can result in various bad consequences later.
> The patch causes mtk_nfc_nand_chip_init() to fail for negative values of
> nsels.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
> ---
>  drivers/mtd/nand/raw/mtk_nand.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
> index ad1b55dab211..df98a2eec240 100644
> --- a/drivers/mtd/nand/raw/mtk_nand.c
> +++ b/drivers/mtd/nand/raw/mtk_nand.c
> @@ -1376,7 +1376,7 @@ static int mtk_nfc_nand_chip_init(struct device *dev, struct mtk_nfc *nfc,
>  		return -ENODEV;
>  
>  	nsels /= sizeof(u32);
> -	if (!nsels || nsels > MTK_NAND_MAX_NSELS) {
> +	if (nsels <= 0 || nsels > MTK_NAND_MAX_NSELS) {
>  		dev_err(dev, "invalid reg property size %d\n", nsels);
>  		return -EINVAL;
>  	}

Thanks,
Miquèl