linux-kernel - Re: [PATCH RESEND] initramfs: cleanup incomplete rootfs

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Date:   Tue, 12 Feb 2019 12:43:17 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     David Engraf <david.engraf@...go.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Arnd Bergmann <arnd@...db.de>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] initramfs: cleanup incomplete rootfs

On Mon, Feb 11, 2019 at 2:40 PM David Engraf <david.engraf@...go.com> wrote:
> On 11.02.19 at 12:40, Andy Shevchenko wrote:
> > On Mon, Feb 11, 2019 at 10:49 AM David Engraf <david.engraf@...go.com> wrote:
> >> On 11.02.19 at 08:56, David Engraf wrote:
> >>> On 09.02.19 at 11:35, Andy Shevchenko wrote:
> >>>> On Sat, Feb 9, 2019 at 12:08 AM Andrew Morton
> >>>> <akpm@...ux-foundation.org> wrote:
> >>>>> On Fri, 8 Feb 2019 21:45:21 +0200 Andy Shevchenko
> >>>>> <andy.shevchenko@...il.com> wrote:
> >>>>>> On Tue, Oct 30, 2018 at 5:22 PM David Engraf
> >>>>>> <david.engraf@...go.com> wrote:

> >>>> In my case I have got "Junk in compressed archive". I don't know (I
> >>>> would check if needed) which exact condition I got  since there are
> >>>> three places with this message. The file itself smaller than the size
> >>>> passed through bootparam. So, when decomression is finished
> >>>> (successfully!) we still have a garbarge in the memory which is not
> >>>> related to archive. Message per se is okay to have, though I consider
> >>>> this non-fatal.
> >>>
> >>> I can reproduce this special case. The unpacking decompresses the whole
> >>> size instead of checking the archive size. I will have a look how to get
> >>> the real archive size.
> >>
> >> I did some checks and manually increased the initramfs size but I always
> >> get the following kernel panic:
> >
> > We need to be on the same page here.
> > There are two sizes of initramfs compressed archive:
> >   1) actual file size;
> >   2) what is declared by boot loader and provided via boot parameters.
> >
> > In my case I have the 2) bigger than the actual file size.
> > Kernel decompresses the initramfs, prints an error that there is junk,
> > which is understandable and continues to run init, etc.
>
> Ok got it. When the memory behind the actual file size is clear (0x0)
> the decompression doesn't complain and just ignores the padding. Any
> other data will be interpreted as a new archive and thus you'll see the
> error message.

Correct.

> Is it possible for you to fill the padding after the actual file size
> with 0x00 ?

Not sure. This is boot loader realm. Even if I patch U-Boot, not every
boot loader will guarantee this.
So, it's fragile to rely on data being 0x00 after actual archive.

-- 
With Best Regards,
Andy Shevchenko