Created attachment 361382 [details]
PATCH: fix mdmon segfault

mdmon was creating a supertype struct with malloc, and thus not necessarily
getting zero-d memory.

This was causing it to segfault when called like this from the initrd:
/sbin/mdmon /proc/mdstat /sysroot

The problem was that  load_super_imsm would get called on the non-zero'd
super struct, whcih in turn calls free_super_imsm, which checks st->sb, which
should be zero but isn't and then starts freeing bogus memory.

The attached patch fixes this by using calloc instead of malloc.

This is a rather big problem as mdmon crashing can cause tasks writing to the
disk to hang forever, see bug 523422.