[Bug 829061] Re: [SRU] double free of mpp->dmi in free_multipath()

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** Branch linked: lp:~dannf/ubuntu/natty/multipath-tools/lp829061

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Title:
  [SRU] double free of mpp->dmi in free_multipath()

Status in “multipath-tools” package in Ubuntu:
  New

Bug description:
  I obtained a coredump from a system where natty's multipathd had
  crashed and received the following backtrace:

  0 0x00007f802925da75 in *__GI_raise (sig=<value optimized out>)
      at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
  #1 0x00007f80292615c0 in *__GI_abort () at abort.c:92
  #2 0x00007f80292974fb in __libc_message (do_abort=<value optimized out>,
      fmt=<value optimized out>) at ../sysdeps/unix/sysv/linux/libc_fatal.c:189
  #3 0x00007f80292a15b6 in malloc_printerr (action=3,
      str=0x7f8029374c70 "double free or corruption (fasttop)",
      ptr=<value optimized out>) at malloc.c:6266
  #4 0x00007f80292a7e83 in *__GI___libc_free (mem=<value optimized out>)
      at malloc.c:3738
  #5 0x00000000004173a5 in xfree (p=0x147bcb0) at memory.c:52
  #6 0x00000000004286cd in free_multipath (mpp=0x14ce1b0, free_paths=0)
      at structs.c:172
  #7 0x0000000000429285 in remove_map (mpp=0x14ce1b0, vecs=0x147b620,
      stop_waiter=0, purge_vec=1) at structs_vec.c:141
  #8 0x0000000000404e06 in ev_add_path (devname=0x16fae48 "sdi", vecs=0x147b620)
      at main.c:438
  #9 0x0000000000404913 in uev_add_path (dev=0x16fabc0, vecs=0x147b620)
      at main.c:327
  #10 0x000000000040584c in uev_trigger (uev=0x7f801c009940,
      trigger_data=0x147b620) at main.c:684
  #11 0x000000000042b679 in service_uevq () at uevent.c:77
  #12 0x000000000042b714 in uevq_thread (et=0x0) at uevent.c:101
  ---Type <return> to continue, or q <return> to quit---
  #13 0x00007f8029e579ca in start_thread () from /lib/libpthread.so.0
  #14 0x00007f802931070d in clone ()
      at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
  #15 0x0000000000000000 in ?? ()

  So it looks like we are trying to free a non-NULL value here:

   if (mpp->dmi)
    FREE(mpp->dmi);

  What's suspicious is that, after freeing that, we don't set it to
  NULL.

  I took a look at upstream git, and found that they do now set it to
  NULL after freeing it. This was part of the following commit:

  commit b7ca0eaae6ccd8dca60df3e2ee93220eadd691ee
  Author: Hannes Reinecke <hare at suse.de>
  Date: Wed Jan 28 09:24:10 2009 +0100

      Plug memory leaks

      Running the internal memory checker revealed quite some memory
      leaks.

      Signed-off-by: Hannes Reinecke <hare at suse.de>

  Note that this change is already included in oneiric.

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