On Tue, 26 Mar 2019, Saidi, Ali wrote:
> On 3/21/19, 9:11 AM, "linux-arm-kernel on behalf of Thomas Gleixner"
> <linux-arm-kernel-boun...@lists.infradead.org on behalf of
> t...@linutronix.de> wrote:
>
> On Tue, 12 Mar 2019, Ali Saidi wrote:
>
> > Increase mmap_base by the worst-case brk randomization so that
> > the stack and heap remain apart.
> >
> > In Linux 4.13 a change was committed that special cased the kernel ELF
> > loader when the loader is invoked directly (eab09532d400; binfmt_elf:
> use
> > ELF_ET_DYN_BASE only for PIE). Generally, the loader isn’t invoked
> > directly and this issue is limited to cases where it is, (e.g to set a
> > non-inheritable LD_LIBRARY_PATH, testing new versions of the loader). In
> > those rare cases, the loader doesn't take into account the amount of brk
> > randomization that will be applied by arch_randomize_brk(). This can
> > lead to the stack and heap being arbitrarily close to each other.
>
> That explains not why you need this change. What's the consequence of them
> being close to each other?
>
> The process doesn't get it's requested stack size and stack allocations
> could end up scribbling on the heap.
And exactly that information wants to be in the changelog.
Thanks,
tglx
