Description of problem:

Unsafe lvm2lib initialisation between two plugins cause memory corruption and dmeventd crash.

Version-Release number of selected component (if applicable):

lvm2-2.02.56-5.el5
device-mapper-1.02.39-1.el5

How reproducible:

1) run dmeventd in foreground mode "dmeventd -d" 

2)create VG with two mirrors and two snapshots, e.g.

# lvs vg_bar
  LV     VG     Attr   LSize Origin Snap%  Move Log        Copy%  Convert
  lv1    vg_bar owi-a- 4.00M
  lv1_s1 vg_bar swi-a- 4.00M lv1      0.20
  lv1_s2 vg_bar swi-a- 4.00M lv1      0.20
  lv2m   vg_bar mwi-a- 4.00M                    lv2m_mlog  100.00
  lv2m2  vg_bar mwi-a- 4.00M                    lv2m2_mlog 100.00

3) Activate and deactivate all volumes:
while :; do vgchange -a n vg_bar ; vgchange -a y vg_bar ; done

4) Enjoy the crash
# dmeventd -d     
You have a memory leak (not released memory pool):
 [0x9a5d458]                                      
 [0x9a5d478]                                      
 [0x9a5df48]                                      
 [0x9a5df68]                                      
 [0x9a83380]                                      
 [0x9a835a8]                                      
 [0x9a839d0]                                      
 [0x9a844d0]                                      
 [0x9a6c4c8]                                      
device-mapper: waitevent ioctl failed: Interrupted system call
You have a memory leak (not released memory pool):            
 [0x9a83380]                                                  
*** glibc detected *** dmeventd: realloc(): invalid next size: 0x09a73710 ***
======= Backtrace: =========                                                 
/lib/libc.so.6[0x7ff851]                                                     
/lib/libc.so.6(realloc+0xe6)[0x800276]                                       
/usr/lib/liblvm2cmd.so.2.02[0x1769be]                                        
/usr/lib/liblvm2cmd.so.2.02[0x176ad8]                                        
/usr/lib/liblvm2cmd.so.2.02[0x177845]                                        
/usr/lib/liblvm2cmd.so.2.02[0x1912f7]                                        
/usr/lib/liblvm2cmd.so.2.02(lvm2_init+0x1e)[0x19133e]                        
/lib/libdevmapper-event-lvm2mirror.so(register_device+0x9b)[0x6b3bbb]        
dmeventd[0x804aea9]
dmeventd(main+0xc93)[0x804be23]
/lib/libc.so.6(__libc_start_main+0xdc)[0x7a9e9c]

Expected results:

lvm2_init and lvm2_exit (and internal constructors/destructors) must use some kind od reference counting or globally allocated structs must be moved into command context.