linux-kernel - Re: [Bug 206175] Fedora >= 5.4 kernels instantly freeze on boot without producing any display output

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Message-ID: <CAHk-=widmu42C4eTQ9uDM+njZE1s5ARmx7E+1SHH1XznTFOwyg@mail.gmail.com>
Date:   Wed, 11 Mar 2020 08:57:56 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Artem S. Tashkinov" <aros@....com>
Cc:     Christoph Hellwig <hch@....de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        iommu <iommu@...ts.linux-foundation.org>
Subject: Re: [Bug 206175] Fedora >= 5.4 kernels instantly freeze on boot
 without producing any display output

On Wed, Mar 11, 2020 at 8:53 AM Artem S. Tashkinov <aros@....com> wrote:
>
> I'm not sure I can call or do anything because the system is dead and
> I'm looking at the kernel panic message. The console is dead. The root
> file system is not yet mounted. Initrd can't be loaded either. I have no
> COM port/console. I have no debugging abilities whatsoever. I can only
> compile kernels and try running them.

Christoph just wanted you to use the image you booted with - you can
do it while using a working and entirely unrealted kernel.

But I think Christoph's second email was right on the money: the
platform device code used to (accidentally) always use that special
kmalloc()'ed memory, and the "always use kfree() to release" then
happened to work.

But with the change, platform devices use that allocations inside the
platform device itself, and the kfree() now does bad things and
corrupts the kmalloc lists.

So that finally makes sense of why that commit would cause odd
problems for you. I'm actually surprised it didn't cause problems for
others, but it's an error path, and presumably it normally never
triggers.

                Linus

              Linus