Re: [PATCH] cmd: sf: prevent overwriting the reserved memory

[Michal Simek <michal.simek@amd.com>]

On 8/9/24 16:44, Simon Glass wrote:
> Hi Michal,
> 
> On Thu, 8 Aug 2024 at 23:39, Michal Simek <michal.simek@amd.com> wrote:
>>
>> Hi Simon,
>>
>> On 8/8/24 16:28, Simon Glass wrote:
>>> Hi Michal,
>>>
>>> On Wed, 7 Aug 2024 at 23:31, Michal Simek <michal.simek@amd.com> wrote:
>>>>
>>>>
>>>>
>>>> On 8/7/24 16:36, Simon Glass wrote:
>>>>> Hi Prasad,
>>>>>
>>>>> On Tue, 6 Aug 2024 at 23:05, Kummari, Prasad <Prasad.Kummari@amd.com> wrote:
>>>>>>
>>>>>> Hi Glass,
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: Simon Glass <sjg@chromium.org>
>>>>>>> Sent: Wednesday, August 7, 2024 3:21 AM
>>>>>>> To: Kummari, Prasad <Prasad.Kummari@amd.com>
>>>>>>> Cc: u-boot@lists.denx.de; git (AMD-Xilinx) <git@amd.com>; Simek, Michal
>>>>>>> <michal.simek@amd.com>; Abbarapu, Venkatesh
>>>>>>> <venkatesh.abbarapu@amd.com>; git@xilinx.com;
>>>>>>> jagan@amarulasolutions.com; n-francis@ti.com; d-gole@ti.com
>>>>>>> Subject: Re: [PATCH] cmd: sf: prevent overwriting the reserved memory
>>>>>>>
>>>>>>> Caution: This message originated from an External Source. Use proper
>>>>>>> caution when opening attachments, clicking links, or responding.
>>>>>>>
>>>>>>>
>>>>>>> Hi Prasad,
>>>>>>>
>>>>>>> On Tue, 6 Aug 2024 at 06:08, Prasad Kummari <prasad.kummari@amd.com> wrote:
>>>>>>>>
>>>>>>>> Added LMB API to prevent SF command from overwriting reserved memory
>>>>>>>> areas. The current SPI code does not use LMB APIs for loading data
>>>>>>>> into memory addresses. To resolve this, LMB APIs were added to check
>>>>>>>> the load address of an SF command and ensure it does not overwrite
>>>>>>>> reserved memory addresses. Similar checks are used in TFTP, serial
>>>>>>>> load, and boot code to prevent overwriting reserved memory.
>>>>>>>
>>>>>>> The SPI flash may be used to load other things, not just an OS. What is your
>>>>>>> use case or problem here?
>>>>>>
>>>>>> [Prasad]:  We have observed that SF command can overwrite the reserved area without throwing any errors or warnings.
>>>>>>     This issue was noticed when the TF-A area is reserved in the Device Tree at address 0xf000000. The sf command is
>>>>>>     corrupting the reserved area,  and U-Boot relocation address too.
>>>>>>
>>>>>> EX: TF-A reserved at ddr address 0xf000000
>>>>>>
>>>>>>          Versal NET> sf read 0x0f000000 0x0 0x100     ----> Overwriting reserved area.
>>>>>>          device 0 offset 0x0, size 0x100
>>>>>>          SF: 256 bytes @ 0x0 Read: OK
>>>>>>
>>>>>>         U-boot relocation address relocaddr   = 0x000000007fec2000
>>>>>>
>>>>>>          Versal NET> sf write 0x0000000077ec2000 0x0 0x100   --> Overwriting reserved area.
>>>>>>          device 0 offset 0x0, size 0x100
>>>>>>          SF: 256 bytes @ 0x0 Written: OK
>>>>>
>>>>> Yes. There are many things which can overwrite memory, e.g. the mw
>>>>> command. It is a boot loader so this is normal.
>>>>>
>>>>> What image are you loading here?
>>>>
>>>> In spi boot it can be Kernel/rootfs but at the end of day it doesn't really matter.
>>>
>>> OK, in that case yes it should use lmb. That was the question I was
>>> trying to understand.
>>>
>>>>
>>>> We have protection for srec, fs load, tftp and wget already.
>>>>
>>>> c6855195e4b4 ("loads: Block writes into LMB reserved areas of U-Boot")
>>>> aa3c609e2be5 ("fs: prevent overwriting reserved memory")
>>>> a156c47e39ad ("tftp: prevent overwriting reserved memory")
>>>> 04592adbdb99 ("net: wget: prevent overwriting reserved memory")
>>>>
>>>> And this is just +1 patch to protect sf command that it doesn't touch reserved
>>>> location.
>>>> The same code should be used for other commands(nand, usb, etc) which loading
>>>> block of data to memory because all of them shouldn't rewrite reserved memory.
>>>>
>>>> In connection to mw/mtest/etc command protection can be also done but not sure
>>>> if this is useful because you normally not using them for booting.
>>>
>>> Exactly.
>>>
>>> I am hoping that we can pull SPI flash into bootstd...has anyone
>>> looked at that? Are you using scripts or is there a special bootmeth?
>>
>> We didn't find this issue in connection to boot. As I wrote in another reply we
>> found it via spi testcases where TF-A was placed lower in DDR and test overwrite
>> it without any other evidence. Part of the reason is that protection units are
>> not enabled to protect secure FW.
> 
> Do you mean the sandbox test test/dm/sf.c ? Or something else? If the
> former, then we could mark dm_test_spi_flash() with CONFIG_SANDBOX

pytest one and I think it was this one.
https://github.com/Xilinx/u-boot-xlnx/blob/master/test/py/tests/test_spi.py

Love is working on sending this test upstream as he did with others.

Thanks,
Michal