The do_openrc() function was not waiting properly for the child process
which started the runlevel to return. We need to repeatedly call
waitpid() until its return value matches the pid of the child process or
the child process does not exist.
This fixes#216.
This fixes#300.
How to reproduce 1-byte overflow:
```
$ FEATURES=-test CFLAGS="-fsanitize=address -O0 -ggdb3" emerge -1 openrc
=================================================================
==1==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fff0efd8710
at pc 0x000000402076 bp 0x7fff0efd7d50 sp 0x7fff0efd7d40
WRITE of size 1 at 0x7fff0efd8710 thread T0
#0 0x402075 (/sbin/openrc-init+0x402075)
#1 0x3cf6e2070f in __libc_start_main (/lib64/libc.so.6+0x3cf6e2070f)
#2 0x4013b8 (/sbin/openrc-init+0x4013b8)
Address 0x7fff0efd8710 is located in stack of thread T0 at offset 2432 in frame
#0 0x401cfb (/sbin/openrc-init+0x401cfb)
This frame has 3 object(s):
[32, 160) 'signals'
[192, 344) 'sa'
[384, 2432) 'buf' <== Memory access at offset 2432 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow ??:0 ??
```
The problem here is in the code handling reads from 'init.ctl':
```
int main(int argc, char **argv) {
...
char buf[2048];
for (;;) {
/* This will block until a command is sent down the pipe... */
fifo = fopen(RC_INIT_FIFO, "r");
count = fread(buf, 1, 2048, fifo);
buf[count] = 0;
...
}
```
`buf[count] = 0;` writes outside the buffer when `fread()` returns non-truncated read.
This fixes#138.
openrc-init.c and openrc-shutdown.c are based on code which was written by
James Hammons <jlhamm@acm.org>, so I would like to publically
thank him for his work.
