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Bug 1219864 - grub2 cannot boot a compressed disk image via memdisk
Summary: grub2 cannot boot a compressed disk image via memdisk
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: grub2
Version: 7.2
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Peter Jones
QA Contact: Release Test Team
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2015-05-08 13:48 UTC by Daphne Shaw
Modified: 2016-11-04 03:58 UTC (History)
2 users (show)

Fixed In Version: grub-2.02-0.35.el7
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-11-04 03:58:18 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
memdisk-freedos-gz.png (28.42 KB, image/png)
2016-02-08 13:27 UTC, Pavel Holica 		no flags Details
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2016:2336 0 normal SHIPPED_LIVE grub2 bug fix and enhancement update 2016-11-03 13:45:27 UTC

Description Daphne Shaw 2015-05-08 13:48:01 UTC 
Description of problem:

One solution to the problem of firmware (BIOS, etc) updater programs being only available for Windows or DOS is to use memdisk to boot a FreeDOS image containing the updater.  Something like:

 menuentry "BIOS updater" {
   linux16 /memdisk iso
   initrd16 /updater.iso
 }

This works fine, but if the image is compressed (memdisk supports both zip and gzip), there is a decompression error and the image cannot be booted.  This worked correctly in legacy grub.

Version-Release number of selected component (if applicable):

grub2-2.02-0.16.el7

Steps to Reproduce:
1. Try and boot a compressed memdisk image.  It will fail if the the image size is not a multiple of 4.
Comment 1 Daphne Shaw 2015-05-08 13:49:19 UTC 
I have worked with the grub2 people, and they acknowledge the bug.  A fix was just committed:

commit a8c473288d3f0a5e17a903a5121dea1a695dda3b
Author: Andrei Borzenkov <arvidjaar>
Date:   Thu May 7 20:24:24 2015 +0300

    loader/linux: do not pad initrd with zeroes at the end
    
    Syslinux memdisk is using initrd image and needs to know uncompressed
    size in advance. For gzip uncompressed size is at the end of compressed
    stream. Grub padded each input file to 4 bytes at the end, which means
    syslinux got wrong size.
    
    Linux initramfs loader apparently does not care about trailing alignment.
    So change code to align beginning of each file instead which atomatically
    gives us the correct size for single file.
    
    Reported-By: David Shaw <dshaw>
Comment 3 Daphne Shaw 2015-12-17 20:52:20 UTC 
Updating version.  Problem still exists in grub2-2.02-0.33.el7_2.x86_64.rpm.
Comment 4 Pavel Holica 2016-02-08 13:27:58 UTC 
Created attachment 1122174 [details]
memdisk-freedos-gz.png

Hello David,

is this the error you're seeing (see attachment)?

I've tried to start freedos floppy disk image without compression (which worked) and with gz compression which failed with attached screenshot.

Thanks
Comment 5 Daphne Shaw 2016-02-08 15:56:28 UTC 
Correct, that's the error I'm getting.  Just like with your test, an uncompressed image works fine, and a compressed image gives that error.

There is some more discussion of the issue at http://lists.gnu.org/archive/html/grub-devel/2015-04/msg00095.html
Comment 6 Pavel Holica 2016-02-09 07:48:32 UTC 
Great, thank you.

Adding qa_ack then.
Comment 10 errata-xmlrpc 2016-11-04 03:58:18 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2336.html
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