linux-kernel - Re: arm64: perf test 26 rpi4 oops

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Date:   Sun, 30 Jul 2023 18:09:15 +0200
From:   Mike Galbraith <efault@....de>
To:     Will Deacon <will@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: arm64: perf test 26 rpi4 oops

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