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

[Simon Glass]

Hi Michal,

On Fri, 9 Aug 2024 at 08:47, Michal Simek <michal.simek at amd.com> wrote:
>
>
>
> On 8/9/24 16:44, Simon Glass wrote:
> > Hi Michal,
> >
> > On Thu, 8 Aug 2024 at 23:39, Michal Simek <michal.simek at 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 at 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 at amd.com> wrote:
> >>>>>>
> >>>>>> Hi Glass,
> >>>>>>
> >>>>>>> -----Original Message-----
> >>>>>>> From: Simon Glass <sjg at chromium.org>
> >>>>>>> Sent: Wednesday, August 7, 2024 3:21 AM
> >>>>>>> To: Kummari, Prasad <Prasad.Kummari at amd.com>
> >>>>>>> Cc: u-boot at lists.denx.de; git (AMD-Xilinx) <git at amd.com>; Simek, Michal
> >>>>>>> <michal.simek at amd.com>; Abbarapu, Venkatesh
> >>>>>>> <venkatesh.abbarapu at amd.com>; git at xilinx.com;
> >>>>>>> jagan at amarulasolutions.com; n-francis at ti.com; d-gole at 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 at 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.

OK. But why is TF-A low in RAM? We really need to have a think about
this TF-A thing. This is the second problem I've seen in a week (the
first was rockchip resetting the timer). Is there a spec for what TF-A
is supposed to do / not do?

Regards,
Simon