Re: arm64: perf test 26 rpi4 oops

[Mike Galbraith]

On Fri, 2023-07-28 at 15:18 +0100, Will Deacon wrote:
>
> Looking at this quickly with Mark, the most likely explanation is that
> a bogus kernel address is being passed as the source pointer to
> copy_to_user().

'start' in read_kcore_iter() is bogus a LOT when running perf test 26,
and that back to at least 5.15.  Seems removal of bogon-proofing gave a
toothless old bug teeth, but seemingly only to perf test 26.  Rummaging
around with crash vmlinux /proc/kcore seems to be bogon free anyway.

Someone should perhaps take a peek at perf.  Bogons aside, it also
doesn't seem to care deeply about kernel response.  Whether the kernel
oops or I bat 945 bogons aside, it says 'OK'.  That seems a tad odd.

	-Mike