Re: [parted-devel] parted crashed on reading DM device without target

[Jim Meyering]

Mike Hwang <mike.hw...@iqstor.com.cn> wrote:
> I found a bug.
>
> In libparted/arch/linux.c:333
>
>
>         next = dm_get_next_target(dmt, NULL, &start, &length,
>                                   &target_type, &params);
>
>         arch_specific->dmtype = strdup(target_type);
>
> Once we have DM name with empty target, 'target_type' will be NULL and
> the program will crash at strdup.
>
> FYI: DM device with empty target could be created with command 'dmsetup
> create'. Once the command prompt for target input, type ctrl-D

Hi Mike,

Thank you for the fine bug report.

At first I was unable to reproduce it, because I had not
specifically configured with --enable-device-mapper.

  [ This is yet another reason to make that the default,
    when the prerequisites are available.. ]

My failed attempt to reproduce went like this:

  # :|dmsetup create no-target
  # parted/parted -m -s /dev/mapper/no-target p
  Warning: Unable to determine geometry of file/device /dev/mapper/no-target.\
  You should not use Parted unless you REALLY know what you're doing!
  Error: /dev/mapper/no-target: unrecognised disk label

Once I rebuilt with --enable-device-mapper, I hit the failure:

  # parted/parted -m -s /dev/mapper/no-target p
  ...
  zsh: segmentation fault  sudo parted/parted -m -s /dev/mapper/no-target p

And repeating after the fix, I get the expected error, as before.

Here's how I've fixed it:


>From e94d23fb1e226beaf3ce02fee9c2f69eb5636674 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@redhat.com>
Date: Fri, 13 Feb 2009 12:08:13 +0100
Subject: [PATCH] don't segfault on a device-mapper device with no target

* libparted/arch/linux.c (_dm_maptype): Don't dereference NULL
for a device-mapper device with no target.  Use the string
"NO-TARGET" instead.  Reported by Mike Hwang in
http://thread.gmane.org/gmane.comp.gnu.parted.devel/2432
---
 libparted/arch/linux.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/libparted/arch/linux.c b/libparted/arch/linux.c
index da812d5..4a8c9e7 100644
--- a/libparted/arch/linux.c
+++ b/libparted/arch/linux.c
@@ -348,7 +348,7 @@ _dm_maptype (PedDevice *dev)
         next = dm_get_next_target(dmt, NULL, &start, &length,
                                   &target_type, &params);

-        arch_specific->dmtype = strdup(target_type);
+        arch_specific->dmtype = strdup(target_type ? target_type : 
"NO-TARGET");
         if (arch_specific->dmtype == NULL)
                 goto bad;
         r = 0;
--
1.6.2.rc0.226.gf08f

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