[PATCH] libparted: avoid unwarranted failed assertion during mklabel

[Jim Meyering]

Testing on RHEL6.2, I found that

When running tests/t9050-partition-table-types.sh with a simulated
sector size of 1024, we'd get a failed assertion in mac.c.
This is done as part of a top-level "make check",
but so far, this failure has shown up only on RHEL-6.2.

Program received signal SIGABRT, Aborted.
0x0000003e35632885 in raise (sig=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
64        return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
Missing separate debuginfos, use: debuginfo-install libgcc-4.4.6-3.el6.x86_64 
libudev-147-2.40.el6.x86_64
(gdb) bt
#0  0x0000003e35632885 in raise (sig=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x0000003e35634065 in abort () at abort.c:92
#2  0x00007ffff7db1bd8 in ped_assert (
    cond_text=0x7ffff7de9e40 "i <= disk->dev->sector_size / 512",
    file=0x7ffff7de9b01 "mac.c", line=707,
    function=0x7ffff7dea310 "_disk_analyse_ghost_size") at debug.c:111
#3  0x00007ffff7dd396b in _disk_analyse_ghost_size (disk=0x619a70) at mac.c:707
#4  0x00007ffff7dd3a84 in mac_read (disk=0x619a70) at mac.c:749
#5  0x00007ffff7db524d in ped_disk_new (dev=0x61aa40) at disk.c:199
#6  0x0000000000404b47 in do_mklabel (dev=0x7fffffffe2c0) at parted.c:493
#7  0x0000000000404029 in command_run (cmd=0x614c10, dev=0x7fffffffe2c0)
    at command.c:139
#8  0x000000000040cd4e in non_interactive_mode (dev=0x7fffffffe2c0,
    cmd_list=0x6121e0, argc=2, argv=0x7fffffffe3d0) at ui.c:1640
#9  0x0000000000408fac in main (argc=2, argv=0x7fffffffe3d0) at parted.c:2172


  690     static int
  691     _disk_analyse_ghost_size (PedDisk* disk)
  692     {
  693             MacDiskData*            mac_disk_data = disk->disk_specific;
  694
  695             void *buf = ped_malloc (disk->dev->sector_size);
  696             if (!buf)
  697                     return 0;
  698
  699             int i;
  700             int found = 0;
  701             for (i = 1; i < 64; i *= 2) {
  702                     if (!ped_device_read (disk->dev, buf, i, 1))
  703                             break;
  704                     if (_rawpart_check_signature (buf)
  705                         && !_rawpart_is_void (buf)) {
  706                             mac_disk_data->ghost_size = i;
 >707                             PED_ASSERT (i <= disk->dev->sector_size / 
 >512);
  708                             found = 1;
  709                             break;
  710                     }
  711             }
  712             free (buf);

(gdb) p i
$1 = 4
(gdb) p disk->dev->sector_size
$2 = 1024

Here's the fix:

>From 4559c510f02a691d90329fd646e8eefe2e73e6d2 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Sun, 26 Feb 2012 18:04:37 +0100
Subject: [PATCH] libparted: avoid unwarranted failed assertion during mklabel

This could happen when running "parted -s $dev mklabel $type" for
nearly any $type, assuming the underlying disk's sector size is
larger than 512 bytes.  This particular failure was noticed by
running tests/t9050-partition-table-types.sh with a simulated
sector size of 1024, as is done as part of a top-level "make check",
but so far, this failure has shown up only on RHEL-6.2.
That test attempts to exercise an ugly part of partition table
creation: during creation, parted checks for an existing
partition table by iterating through its list of known types and
attempting to read the disk, looking for a preexisting table.
Knowing this, the test takes all pairs of partition table types,
<A,B> and first creates a type of type A, and then creates on top
of that (erasing the original) a table of type B.
* libparted/labels/mac.c (_disk_analyse_ghost_size): Remove bogus
assertion.  If the number of the sector with a matching signature
is too large, simply reject it by returning 0.
* NEWS (Bug fixes): Mention this.
---
 NEWS                   |    3 +++
 libparted/labels/mac.c |    3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index fc93e98..50d9126 100644
--- a/NEWS
+++ b/NEWS
@@ -71,6 +71,9 @@ GNU parted NEWS                                    -*- 
outline -*-
   of partitions the device can hold.  With this change, parted now correctly
   informs kernel about new partitions on partitionable MD RAID devices.

+  libparted: creating a new partition table on a device with an existing
+  mac partition table could result in a failed assertion.
+
 ** Changes in behavior

   Floppy drives are no longer scanned on linux: they cannot be partitioned
diff --git a/libparted/labels/mac.c b/libparted/labels/mac.c
index 41ea398..1f59a1a 100644
--- a/libparted/labels/mac.c
+++ b/libparted/labels/mac.c
@@ -704,8 +704,7 @@ _disk_analyse_ghost_size (PedDisk* disk)
                if (_rawpart_check_signature (buf)
                    && !_rawpart_is_void (buf)) {
                        mac_disk_data->ghost_size = i;
-                       PED_ASSERT (i <= disk->dev->sector_size / 512);
-                       found = 1;
+                       found = (i <= disk->dev->sector_size / 512);
                        break;
                }
        }
--
1.7.9.2.263.g9be8b7