No, if a process allocates an infeasible amount, malloc fails and the process needs to deal with the failure (which is what already happens, "malloc doesn't fail on Linux" is only really true for smaller-than-page-size allocations). The point being made is that the system should account conservatively for all memory that can be used, not just the optimistic underestimate that overcommit enables (i.e. the plane should always carry enough fuel for contingencies, and landing with extra fuel is a good outcome).

You never need to crash the system if you remove overcommit. You just crash the one process. Practically speaking, you don't even need to crash here; you just return null (which malloc is always free to do) and let the consequences speak for themselves.

malloc can just return NULL (in specific, mmap returns -ENOMEM and your libc translates that). Applications need to check for success anyway