> On Sep 8, 2021, at 6:50 PM, Jann Horn <jannh@xxxxxxxxxx> wrote: > > On Thu, Sep 9, 2021 at 2:16 AM Prakash Sangappa > <prakash.sangappa@xxxxxxxxxx> wrote: >> A structure per thread is allocated from a page that is shared mapped >> between user space and kernel as means for faster communication. This will >> facilitate sharing information, Ex: per thread stats shared between kernel >> and user space, that can be read by applications without the need for >> making frequent system calls in latency sensitive code path. > [...] >> + /* Try to map as high as possible, this is only a hint. */ >> + pg->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, >> + PAGE_SIZE, 0, 0); > > I don't have an opinion on the rest of this patch, but from a security > perspective, please don't map things at fixed addresses; let the mmap > code pick some random address that it wants to use. If an attacker > manages to overwrite some userspace pointer with chosen data, we don't > want them to know an address where they can be sure something is > mapped. Sure. I will address this. Thanks, -Prakash
