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Re: [PATCH parted 2/2] linux: Fix use after free in devicemapper code

From: Hans de Goede
Subject: Re: [PATCH parted 2/2] linux: Fix use after free in devicemapper code
Date: Fri, 18 Dec 2009 14:00:32 +0100
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0


On 12/18/2009 01:59 PM, Jim Meyering wrote:
Hans de Goede wrote:
Is this adjustment ok with you, since I'm leaving your name on it?
I don't want to leave the assignments to NULL, since they're
effectively dead code and I don't want to provoke warnings
from the likes of clang and coverity.

I understand the motivation in setting them to NULL,
but since there is obviously no further use of dev_name,
and the next use of "task" is an assignment, it seems safe.

You cannot remove the "task = NULL" statement, otherwise the task will
get destroyed a second time in the error path of the asprintf directly
below the moved "dm_task_destroy (task)"

Oh.  Duh ;-)

I'll fold this into it, also removing a useless initialization.




 From d1f4354cc2bd3ffae2afbb510bafd43f2b6857ba Mon Sep 17 00:00:00 2001
From: Jim Meyering<address@hidden>
Date: Fri, 18 Dec 2009 13:51:41 +0100
Subject: [PATCH] .

  libparted/arch/linux.c |    4 ++--
  1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libparted/arch/linux.c b/libparted/arch/linux.c
index d996f32..aefe788 100644
--- a/libparted/arch/linux.c
+++ b/libparted/arch/linux.c
@@ -2423,7 +2423,6 @@ err:
  static int
  _dm_add_partition (PedDisk* disk, PedPartition* part)
-        struct dm_task* task = NULL;
          int             rc;
          char*           vol_name = NULL;
          const char*     dev_name = NULL;
@@ -2434,7 +2433,7 @@ _dm_add_partition (PedDisk* disk, PedPartition* part)
                  return 0;

          /* Get map name from devicemapper */
-        task = dm_task_create (DM_DEVICE_INFO);
+        struct dm_task *task = dm_task_create (DM_DEVICE_INFO);
          if (!task)
                  goto err;

@@ -2453,6 +2452,7 @@ _dm_add_partition (PedDisk* disk, PedPartition* part)

          /* Caution: dm_task_destroy frees dev_name.  */
          dm_task_destroy (task);
+        task = NULL;

          if (asprintf (&params, "%d:%d %lld", arch_specific->major,
                        arch_specific->minor, part->geom.start) == -1)

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