linux-kernel - Re: [PATCH] phy: ocelot-serdes: fix out-of-bounds read

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Date:   Mon, 8 Oct 2018 22:55:36 +0200
From:   Quentin Schulz <quentin.schulz@...tlin.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phy: ocelot-serdes: fix out-of-bounds read

Hi Gustavo,

On Mon, Oct 08, 2018 at 08:06:49PM +0200, Gustavo A. R. Silva wrote:
> Currently, there is an out-of-bounds read on array ctrl->phys,
> once variable i reaches the maximum array size of SERDES_MAX
> in the for loop.
> 
> Fix this by changing the condition in the for loop from
> i <= SERDES_MAX to i < SERDES_MAX.
> 

Thanks for the heads up. However, as defined today, SERDES_MAX is a
valid value so I need it in the iteration. There are two possible fixes
though:

Either we let all the for loops as `for (i = 0; i <= SERDES_MAX; i++)`
and define ctrl->phys as an array of size SERDES_MAX + 1.

Or we modify the for loops as `for (i = 0; i < SERDES_MAX; i++)` and we
update SERDES_MAX in include/dt-bindings/phy/phy-ocelot-serdes.h to be
SERDES6G_MAX + 1.

As you wish!

Thanks,
Quentin

> Addresses-Coverity-ID: 1473966 ("Out-of-bounds read")
> Addresses-Coverity-ID: 1473959 ("Out-of-bounds read")
> Fixes: 51f6b410fc22 ("phy: add driver for Microsemi Ocelot SerDes muxing")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/phy/mscc/phy-ocelot-serdes.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/phy/mscc/phy-ocelot-serdes.c b/drivers/phy/mscc/phy-ocelot-serdes.c
> index 8936abd..c4eee3a 100644
> --- a/drivers/phy/mscc/phy-ocelot-serdes.c
> +++ b/drivers/phy/mscc/phy-ocelot-serdes.c
> @@ -206,7 +206,7 @@ static struct phy *serdes_simple_xlate(struct device *dev,
>  	port = args->args[0];
>  	idx = args->args[1];
>  
> -	for (i = 0; i <= SERDES_MAX; i++) {
> +	for (i = 0; i < SERDES_MAX; i++) {
>  		struct serdes_macro *macro = phy_get_drvdata(ctrl->phys[i]);
>  
>  		if (idx != macro->idx)
> @@ -260,7 +260,7 @@ static int serdes_probe(struct platform_device *pdev)
>  	if (!ctrl->regs)
>  		return -ENODEV;
>  
> -	for (i = 0; i <= SERDES_MAX; i++) {
> +	for (i = 0; i < SERDES_MAX; i++) {
>  		ret = serdes_phy_create(ctrl, i, &ctrl->phys[i]);
>  		if (ret)
>  			return ret;
> -- 
> 2.7.4
> 

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