Re: [OSS-Tools] [PATCH] libdt: fix of_get_devicepath looking up sibling if device unavailable

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 07.06.23 10:08, Ahmad Fatoum wrote:
> of_get_devicepath code flow is split into two:
> 
>   A) Either the device tree node in question has a direct udev_device
>      associated with it
> 
>   B) Or we assume it's a partition and lookup udev_device for the parent
>      first, before finding a child udev_device or setting a partition
>      offset within the parent udev_device.
> 
> Since v2017.03.0, we have had a fallthrough from case A into case B:
> If we have a udev_device, but it's neither a EEPROMs, MTDs or block
> device, we just consider it a partition. This is problematic, because
> this may result in us pointing at a very different device:
> 
>   - backend points at a SD-Card host. Host is enabled, but SD-Card
>     is not inserted, so no block device
> 
>   - case A fails, so it's assumed it's a partition and case B
>     uses parent SoC bus to lookup appropriate device
> 
>   - We fall through into the second device_find_block_device, which
>     will take the first matching block device across the SoC. So
>     we could end up with the eMMC: a completely different device
>     than what was pointed at.
> 
> Fixes: 929ed64cb42f ("of_get_devicepath: make partition finding more robust")
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

Patch applied to next.

> ---
>  src/libdt.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libdt.c b/src/libdt.c
> index e54d7fb5649d..7b99efe5b2de 100644
> --- a/src/libdt.c
> +++ b/src/libdt.c
> @@ -2492,9 +2492,11 @@ int of_get_devicepath(struct device_node *partition_node, char **devpath, off_t
>  		}
>  
>  		/*
> -		 * If we found a device but couldn't classify it above, we fall
> -		 * through.
> +		 * If we find a udev_device but couldn't classify it above,
> +		 * it's an error. Falling through would mean to handle it as a
> +		 * partition and could lead us to return an arbitrary sibling device
>  		 */
> +		return -ENODEV;
>  	}
>  
>  	/*

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |