linux-kernel - Re: [PATCH] mtd/redboot: avoid null pointer deref

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Message-ID: <8267e170-e3ae-06dd-c859-17712785071a@gmail.com>
Date:   Tue, 3 Jan 2017 03:22:28 +0100
From:   Marek Vasut <marek.vasut@...il.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd/redboot: avoid null pointer deref

On 12/22/2016 12:25 AM, Jason A. Donenfeld wrote:
> By giving a bogus partition name, it's possible to trigger a null
> pointer dereference.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

Nice catch. It'd be great to have the condition which can be used to
trigger this problem in the commit message. I presume this happens if
buf[i].name[0] = 0xff for all $i, right ?

So please expand the explanation and add my Ack for V2:
Acked-by: Marek Vasut <marek.vasut@...il.com>

Thanks

> ---
>  drivers/mtd/redboot.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/redboot.c b/drivers/mtd/redboot.c
> index 7623ac5fc586..53949ef80d36 100644
> --- a/drivers/mtd/redboot.c
> +++ b/drivers/mtd/redboot.c
> @@ -212,6 +212,10 @@ static int parse_redboot_partitions(struct mtd_info *master,
>  
>  		nrparts++;
>  	}
> +	if (!fl) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
>  #ifdef CONFIG_MTD_REDBOOT_PARTS_UNALLOCATED
>  	if (fl->img->flash_base) {
>  		nrparts++;
> 


-- 
Best regards,
Marek Vasut