MMU lkl_phys_mem shm leak

[grant-h]

shm_open is used to allocate a POSIX shm region for physical memory in shmem_init. This file is not closed after final mmap and the kernel will not close it for us leading to SHM exhaustion.

[tavip]

Thanks for the report, looks like we need to add a shm_cleanup host operations and call it from lkl_sys_halt.

[grant-h]

I was thinking it would be best if we could unlink the fd to avoid having shm's leftover if the process crashes (a common case when fuzzing or developing). The issue is that I'm not familiar enough with LKL's initialization to be sure that the only mmap caller would be for bootmem. I see that there is a PTE path that seems it could hit it as well. I'm wondering, what was the reason shm is needed? Multi-process sharing?
Actually fix is easy: just call shm_unlink after creation. as long as another outside process doesn't need to open the memory we can get away with this. The memory won't be freed until the fd refcount reaches zero in the (host) kernel.

[tavip]

Sounds good to me, thanks @grant-h!