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From: Sascha Hauer <s.hauer@pengutronix.de>
To: Stefan Kerkmann <s.kerkmann@pengutronix.de>
Cc: BAREBOX <barebox@lists.infradead.org>
Subject: Re: [PATCH 2/2] of: fdt: fix oob writes with large ftd properties
Date: Thu, 1 Feb 2024 08:47:46 +0100	[thread overview]
Message-ID: <20240201074746.GH406126@pengutronix.de> (raw)
In-Reply-To: <20240131-fix-fdt-memory-safety-v1-2-3d3a2c797eec@pengutronix.de>


In the subject: s/ftd/fdt/

Sascha

On Wed, Jan 31, 2024 at 05:57:00PM +0100, Stefan Kerkmann wrote:
> OOB writes can be triggered when fdt->dt_size * 2 is still smaller than
> the property for which memory should be allocated. This can happen under
> rare circumstances when editing a fdt with the of_property command and a
> property is larger than 128k in size.
> 
> This happend when editing a FIT image (which is a ftd) with the
> of_property command and the Kernel image was around 8M in size.
> 
> The simplified call chain is the following:
> 
> of_property -> of_flatten_dtb -> create new fdt with 64k in size (this is
> fixed) -> __of_flatten_dtb -> attempt to copy kernel image (8M) ->
> fdt_ensure_space -> allocate only 128k for fdt->dt -> memcopy 8M into fdt->dt
> buffer -> crash
> 
> The fix is to grow fdt->dt to hold at least the new property. The power
> of 2 increment is untouched to keep the same behaviour otherwise.
> 
> Signed-off-by: Stefan Kerkmann <s.kerkmann@pengutronix.de>
> ---
>  drivers/of/fdt.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 4f79a6120f..1f24ed0bbc 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -399,6 +399,10 @@ static int fdt_ensure_space(struct fdt *fdt, int dtsize)
>  		previous = fdt->dt;
>  		new_size = fdt->dt_size * 2;
>  
> +		while (new_size <= dtsize) {
> +			new_size *= 2;
> +		}
> +
>  		if ((fdt->dt = memalign_realloc(previous, fdt->dt_size,
>  						new_size)) == NULL) {
>  			free(previous);
> 
> -- 
> 2.39.2
> 
> 

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  parent reply	other threads:[~2024-02-01  7:48 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-31 16:56 [PATCH 0/2] of: fdt: fix memory leak and oob writes in fdt_ensure_space Stefan Kerkmann
2024-01-31 16:56 ` [PATCH 1/2] of: fdt: fix memory leak " Stefan Kerkmann
2024-01-31 17:15   ` Ahmad Fatoum
2024-02-01  8:34     ` Stefan Kerkmann
2024-01-31 16:57 ` [PATCH 2/2] of: fdt: fix oob writes with large ftd properties Stefan Kerkmann
2024-01-31 17:21   ` Ahmad Fatoum
2024-02-01 10:24     ` Stefan Kerkmann
2024-02-01 10:42       ` Ahmad Fatoum
2024-02-01  7:47   ` Sascha Hauer [this message]
2024-02-01  8:49     ` Stefan Kerkmann

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