The kernel is telling you that when the segfault occurred, the instruction pointer 0x7f3c7c523770 was in a SysV IPC shm segment. The shared memory segment started at 0x7f3c7c4e8000 and was 0x60000 bytes long.
SysV shm segments are not backed by a file, so the string SYSV00000000 appears where normally you'd get the filename of the executable or library where the segfault occurred. As a result this log line gives us no real useful information. If you want any hope of tracing the cause of the crash, you need the core dump.
I suspect that the instruction pointer wasn't supposed to be in there at all. It's pretty weird to load executable code into a SysV shm segment. But I haven't seen any XFCE code, so what looks weird to me might be normal there.
You can learn the basics about sysv shm, assuming you have a decent grasp of the basics of memory management by reading these man pages:
man svipc
man shmget
man shmat
Run the ipcs command to see what sysv ipc resources are currently allocated. ipcs -m limits the list to just the shared memory segments.
