On Mon, Jul 12, 2021 at 09:05:45AM +0800, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote: > Let me describe my use case more clearly (just ignore if you're not interested > in it): > > 1. Prog A mmap() 4GB memory (anon or file-mapping), suppose the allocated VA > range is [0x40000000,0x140000000) > > 2. Prog A specifies [0x48000000,0x50000000) and [0x80000000,0x100000000) will be > shared by its child. > > 3. Prog A fork() Prog B and then Prog B exec() a new ELF binary. > > 4. Prog B notice the shared ranges (e.g. by input parameters or ...) and remap > them to a continuous VA range. This is dangerous. There must be an active step for Prog B to accept Prog A's ranges into its address space. Otherwise Prog A could almost completely fill Prog B's address space and so control where Prog B places its mappings. It could also provoke a latent bug in Prog B if it doesn't handle address space exhaustion gracefully. I had a proposal to handle this. Would it meet your requirements? https://lore.kernel.org/lkml/20200730152250.GG23808@xxxxxxxxxxxxxxxxxxxx/
