Subject: Re: [PATCH] fsl/fman: Validate cell-index value obtained from Device Tree

From: Simon Horman <[email-masked]>
Date: Tue, 2 Jul 2024 14:36:51 +0100

On Tue, Jul 02, 2024 at 12:50:34PM +0300, Aleksandr Mishin wrote:
> Cell-index value is obtained from Device Tree and then used to calculate
> the index for accessing arrays port_mfl[], mac_mfl[] and intr_mng[].
> In case of broken DT due to any error cell-index can contain any value
> and it is possible to go beyond the array boundaries which can lead
> at least to memory corruption.
> Validate cell-index value obtained from Device Tree.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 414fd46e7762 ("fsl/fman: Add FMan support")
> Signed-off-by: Aleksandr Mishin <[email-masked]>
> ---
>  drivers/net/ethernet/freescale/fman/fman.c | 7 +++++++
>  drivers/net/ethernet/freescale/fman/fman.h | 2 ++
>  drivers/net/ethernet/freescale/fman/mac.c  | 5 +++++
>  3 files changed, 14 insertions(+)
> 
> diff --git a/drivers/net/ethernet/freescale/fman/fman.c b/drivers/net/ethernet/freescale/fman/fman.c
> index d96028f01770..6929bca3f768 100644
> --- a/drivers/net/ethernet/freescale/fman/fman.c
> +++ b/drivers/net/ethernet/freescale/fman/fman.c
> @@ -2933,3 +2933,10 @@ module_exit(fman_unload);
>  
>  MODULE_LICENSE("Dual BSD/GPL");
>  MODULE_DESCRIPTION("Freescale DPAA Frame Manager driver");
> +
> +int check_mac_id(u32 mac_id)
> +{
> +	if (mac_id >= MAX_NUM_OF_MACS)
> +		return -EINVAL;
> +	return 0;
> +}
> diff --git a/drivers/net/ethernet/freescale/fman/fman.h b/drivers/net/ethernet/freescale/fman/fman.h
> index 2ea575a46675..3cedde4851e1 100644
> --- a/drivers/net/ethernet/freescale/fman/fman.h
> +++ b/drivers/net/ethernet/freescale/fman/fman.h
> @@ -372,6 +372,8 @@ u16 fman_get_max_frm(void);
>  
>  int fman_get_rx_extra_headroom(void);
>  
> +int check_mac_id(u32 mac_id);
> +
>  #ifdef CONFIG_DPAA_ERRATUM_A050385
>  bool fman_has_errata_a050385(void);
>  #endif
> diff --git a/drivers/net/ethernet/freescale/fman/mac.c b/drivers/net/ethernet/freescale/fman/mac.c
> index 9767586b4eb3..7a67b4c887e2 100644
> --- a/drivers/net/ethernet/freescale/fman/mac.c
> +++ b/drivers/net/ethernet/freescale/fman/mac.c
> @@ -247,6 +247,11 @@ static int mac_probe(struct platform_device *_of_dev)
>  		dev_err(dev, "failed to read cell-index for %pOF\n", mac_node);
>  		return -EINVAL;
>  	}
> +	err = check_mac_id(val);

Hi Aleksandr, all,

It seems that this breaks linking with allmodconfig builds on x86_64,
perhaps it is better to simply make check_mac_id a static function in mac.c ?

> +	if (err) {
> +		dev_err(dev, "cell-index value is out of range for %pOF\n", mac_node);

Although other instances exist in this function before this patch,
it does look like this leaks a reference to of_dev taken by the
call to of_find_device_by_node() on line 194.

Maybe it is intentional, I'm unsure.
Perhaps this can be investigated separately to the fix proposed by this
patch?

Flagged by Coccinelle (this one is on line 253):

 .../mac.c:238:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:242:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:248:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:253:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:267:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:273:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:282:3-9: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:320:2-8: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:333:1-7: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:337:1-7: ERROR: missing put_device; call of_find_device_by_node on line 194, but without a corresponding object release within this function.
 .../mac.c:282:3-9: ERROR: missing put_device; call of_find_device_by_node on line 285, but without a corresponding object release within this function.
 .../mac.c:320:2-8: ERROR: missing put_device; call of_find_device_by_node on line 285, but without a corresponding object release within this function.
 .../mac.c:333:1-7: ERROR: missing put_device; call of_find_device_by_node on line 285, but without a corresponding object release within this function.
 .../mac.c:337:1-7: ERROR: missing put_device; call of_find_device_by_node on line 285, but without a corresponding object release within this function.

> +		return err;
> +	}
>  	priv->cell_index = (u8)val;
>  
>  	/* Get the MAC address */

-- 
pw-bot: changes-requested