On Fri, Dec 30, 2016 at 7:56 AM, Dmitry Safonov <dsafo...@virtuozzo.com> wrote: > Add arch_prctl getters/setters for size of virtual address space of task. > This adds ability to change task's virtual address space limit. > I need this for correctly restore virtual address space limits in CRIU. > Currently, on x86 there are three task sizes: 3GB for some old 32 bit java > apps, 4Gb for ordinary 32-bit compatible apps and 47-bits for native > x86_64 processes. > 32-bit applications are restored by CRIU with the help of 64-bit clone()-d > child, and on restore we need to place correct address space limitations > back - otherwise 32-bit restored application may mmap() address over > 4Gb space and as this address will not fit into 4-byte pointer, it > will silently reuse/corrupt the pointer that has the same lower 4-bytes. >
I agree we need something like this, but this particular justification is a bit bogus. If 32-bit mmap() returns an address above 2^32, then I think it's a straight-up bug. The address space limit shouldn't have anything to do with it -- the kernel *knows* that it's a "compat" syscall.
