After update from 22.1.7 to 22.2-rc3 inside VirtualBox, desktop doesn't come up; likely memory corruption in llvmpipe
Mesa 22.2-rc3 works perfectly in various real hardware environments (various AMD, Intel and nouveau boxes), but inside VirtualBox, the update breaks booting to desktops (seen with at least plasma and xfce). The X server or Wayland server (happens with both display systems) comes up, and simple applications like konsole can be launched on it from a tty, but the desktop doesn't come up.
Log files say
plasmashell[1302]: Fatal glibc error: malloc assertion failure in sysmalloc: (old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)
which is a strong indication that there's memory corruption happening somewhere. Since this only happens with Mesa 22.2-rc3 in VirtualBox, the likely culprit is llvmpipe.