Aw: Re: BUG: Bad page map in process/Bad Swap file entry, RPI CM4 on clone syscall

[max.schulze at online.de]

> 
> 
> I think the issue is much more fundamental than that; you appear to have
> page-table corruption (for example, "pte:262d2626292a2627" and
> "pte:1110111111111111" are definitely corrupted) and so anything dealing
> with 'struct page' derived from the physical address in the pte is going to
> go wonky.
> 
>  From the logs here, the pmds look ok but these are the pte values I 
> spotted:
> 
> 0x1110111111111111
> 0x262d2626292a2627
> 0xa098a09aa29ea8a4
> 0x212725231f242323
> 0x2626262023222323
> 
> which don't seem to correspond to any sort of poison, but are possibly
> artifacts of repeated patterns with random bits cleared?
> 
> Will


Very valuable thought. I am streaming camera data, and generally the image captured from my desk is very dark (so these might be 8-bit brightness values from a mono ov9281 sensor).

I then set the camera to generate a test pattern, i.e. it will only produce output  like this

00000090: ffff ffff ffff ffff ffff 00ff 00ff 00ff
000000a0: 00ff 00ff 00ff 00ff 00ff 00ff 00ff 00ff

( also ff00 and 0000 ).

And those were the crashes that followed:

[   54.838582] BUG: Bad page map in process pool-upowerd  pte:ff00ffffffffff pmd:800000001801003
[   54.839187] BUG: Bad page map in process pool-upowerd  pte:ff00ff00ff00ff pmd:800000001801003
[   54.839615] BUG: Bad page map in process pool-upowerd  pte:ff00ff00ff00ff pmd:800000001801003
[   54.845439] BUG: Bad page map in process pool-upowerd  pte:ff00ff00ff00ff pmd:800000001801003

[   49.664066] BUG: Bad page map in process gmain  pte:ff00ffffffffff pmd:800000001801003
[   49.664515] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.664879] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.665245] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.665610] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.665973] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.666336] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.666698] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003
[   49.667061] BUG: Bad page map in process gmain  pte:ff00ff00ff00ff pmd:800000001801003

That confirms my suspicion of a dma write-out-of-bounds from a very separate angle (thanks again for the valuable idea).
I have since taken this to https://github.com/raspberrypi/linux/issues/5138 but will update the list once investigation has found a solution.

Thanks,
Max