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

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 <email address hidden>
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 <email address hidden>

Note that this change is already included in oneiric.