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Bug#851815: marked as done (efivar: Bogus output for MBR partitions (disk signature))

Your message dated Tue, 31 Oct 2017 20:29:26 +0000
with message-id <41d8421e60674b7089e340fca340dbf8@ausx13mpc120.AMER.DELL.COM>
and subject line 
has caused the Debian Bug report #851815,
regarding efivar: Bogus output for MBR partitions (disk signature)
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
851815: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=851815
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Source: efivar
Version: 30-1
Severity: normal
Tags: patch upstream
format_media_dn() produces bogus media device paths for MBR partitions. Instead of displaying the MBR disk signature, the current logic apparently sign-extends its least-significant byte and returns a decimal number, still prefixed with "0x". The result is nonsense like this: 

   # blkid -o value -s PTUUID /dev/sdb
   927a7490
   # efibootmgr -v | grep debian
   Boot0002* debian    HD(3,MBR,0x4294967184,0xe89c0000,0x100000)/File(\EFI\debian\grubx64.efi)
The "0x4294967184" returned by efibootmgr is really *decimal* 4294967184, which is just 0xffffff90. The correct output for this field would be "0x927a7490": 

   # blkid -o value -s PTUUID /dev/sdb
   927a7490
   # efibootmgr -v | grep debian
   Boot0002* debian    HD(3,MBR,0x927a7490,0xe89c0000,0x100000)/File(\EFI\debian\grubx64.efi)

Upstream pull request: https://github.com/rhinstaller/efivar/pull/79

-- System Information:
Debian Release: stretch/sid
 APT prefers unstable
 APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, armhf

Kernel: Linux 4.8.0-2-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

>From e5dd44155fd91d9c3e8b31f897b0dc6ac4635742 Mon Sep 17 00:00:00 2001
From: Dwayne Litzenberger <dlitz@dlitz.net>
Date: Wed, 18 Jan 2017 16:35:46 -0800
Subject: [PATCH] format_media_dn: Fix formatting of disk signature for MBR
 partitions

The previous logic sign-extended the least-significant byte of the disk
signature and returned a decimal number prefixed with "0x", producing
nonsense like this:

    # blkid -o value -s PTUUID /dev/sdb
    927a7490
    # efibootmgr -v | grep debian
    Boot0002* debian HD(3,MBR,0x4294967184,0xe89c0000,0x100000)/File(\EFI\debian\grubx64.efi)
    # python -c 'print hex(4294967184)'
    0xffffff90

With this change, it works properly:

    Boot0002* debian HD(3,MBR,0x927a7490,0xe89c0000,0x100000)/File(\EFI\debian\grubx64.efi)

Signed-off-by: Dwayne Litzenberger <dlitz@dlitz.net>
---
 src/dp-media.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/dp-media.c b/src/dp-media.c
index cde2ad8..6fd8dcf 100644
--- a/src/dp-media.c
+++ b/src/dp-media.c
@@ -36,8 +36,11 @@ _format_media_dn(char *buf, size_t size, const_efidp dp)
 		switch (dp->hd.signature_type) {
 		case EFIDP_HD_SIGNATURE_MBR:
 			format(buf, size, off, "HD",
-			       "MBR,0x%"PRIu32",0x%"PRIx64",0x%"PRIx64")",
-			       *(char *)dp->hd.signature,
+			       "MBR,0x%"PRIx32",0x%"PRIx64",0x%"PRIx64")",
+			       (uint32_t)dp->hd.signature[0] |
+			       ((uint32_t)dp->hd.signature[1] << 8) |
+			       ((uint32_t)dp->hd.signature[2] << 16) |
+			       ((uint32_t)dp->hd.signature[3] << 24),
 			       dp->hd.start, dp->hd.size);
 			break;
 		case EFIDP_HD_SIGNATURE_GUID:
-- 
2.11.0

--- End Message ---
--- Begin Message ---

Fixed by upstream patch included in version 31-1 in Debian.

 

Dwayne, thank you for your efforts getting this upstream, my apologies in forgetting to close it here.


--- End Message ---
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