Re: [PATCH v5] aarch64: enforce >=64K guard size

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 10/01/2020 17:13, Florian Weimer wrote:
> * Szabolcs Nagy:
> 
> > There are several compiler implementations that allow large stack
> > allocations to jump over the guard page at the end of the stack and
> > corrupt memory beyond that. See CVE-2017-1000364.
> >
> > Compilers can emit code to probe the stack such that the guard page
> > cannot be skipped, but on aarch64 the probe interval is 64K by default
> > instead of the minimum supported page size (4K).
> >
> > This patch enforces at least 64K guard on aarch64 unless the guard
> > is disabled by setting its size to 0.  For backward compatibility
> > reasons the increased guard is not reported, so it is only observable
> > by exhausting the address space or parsing /proc/self/maps on linux.
> >
> > On other targets the patch has no effect. If the stack probe interval
> > is larger than a page size on a target then ARCH_MIN_GUARD_SIZE can
> > be defined to get large enough stack guard on libc allocated stacks.
> >
> > The patch does not affect threads with user allocated stacks.
> 
> I think this is okay.  I checked that all architectures still build.
> I filed bug 26691 to help with tracking the backports.  Would you please
> reference this bug in your commit message?

ok, committed at 238032ead6f34c41542890b968d973eb5c839673

thanks for checking.