[U-Boot] [PATCH] phy: Fix u-boot coruption when fixed-phy is used

[Michal Simek]

On 20. 12. 18 14:13, Stefan Roese wrote:
> On 19.12.18 16:57, Michal Simek wrote:
>> When fixed-link phy is used subnode offset is used as phy address. This
>> number is bigger then space allocated for bus structure (allocated via
>> mdio_alloc).
>> bus->phymap[] array has PHY_MAX_ADDR size (32).
>> That's why writing bus->phymap[addr] where addr is < 0 or > PHY_MAX_ADDR
>> is causing write to memory which can caused full U-Boot crash.
>>
>> The patch is checking if address is in correct range.
>>
>> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
>> ---
>>
>> search_for_existing_phy() is using this array but there is if check
>> already that's why it shouldn't be a big deal.
>>
>> ---
>>   drivers/net/phy/phy.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
>> index e837eb7688cc..cda4caa8034d 100644
>> --- a/drivers/net/phy/phy.c
>> +++ b/drivers/net/phy/phy.c
>> @@ -656,7 +656,8 @@ static struct phy_device *phy_device_create(struct
>> mii_dev *bus, int addr,
>>         phy_probe(dev);
>>   -    bus->phymap[addr] = dev;
>> +    if (addr >= 0 && addr < PHY_MAX_ADDR)
>> +        bus->phymap[addr] = dev;
> 
> How about adding some error / warning print in the else path here?

We can add it but I am not quite sure how that error should look like in
this case. Because addr is filled by node offset got from
sn = fdt_first_subnode(gd->fdt_blob, dev_of_offset(dev));

It means this error/warning will be shown all the time which is also weird.

The solution could be to save link to phy DT node in phy_device
structure and then read it on driver not like this
int ofnode = phydev->addr;
which is done in fixed.c

But anyway still that above fix make sense to make sure that we are not
overwriting stuff.

Thanks,
Michal