`mmapInRegion` may loop infinitely
Currently mmapInRegion is susceptible to infinitely loop when the platform's mmap provides memory before the region we are trying to map into. Specifically, its current implementation is:
bool wrapped = false;
int prot = memoryAccessToProt(access);
void *p = region->last;
while (1) {
void *result = doMmap(p, bytes, prot, flags, fd, offset);
if (result == NULL) {
...
} else if (result < region->start) {
p = (uint8_t *) result + bytes; // (a) mmap gave us memory too low, advance and try again
} else if (result < region->end) {
...
} else if (wrapped) {
...
}
// mmap() gave us too high an address; wrap around and try again
munmap(result, bytes);
wrapped = true;
p = region->start; // (b)
}Note how when result < region->start we first advance p (point (a)) and then later reset it to region->start (point (b)).
Additionally, the logic at point (a) is itself highly suspect as we reset p to an address manifestly below region->start.