On Tue, Oct 27, 2020 at 12:09:20AM +0000, Al Viro wrote: > On Mon, Oct 26, 2020 at 06:03:18PM -0600, Jens Axboe wrote: > > The removal of compat_process_vm_{readv,writev} didn't change > > process_vm_rw(), which always assumes it's not doing a compat syscall. > > Instead of passing in 'false' unconditionally for 'compat', make it > > conditional on in_compat_syscall(). > > > > Fixes: c3973b401ef2 ("mm: remove compat_process_vm_{readv,writev}") > > Reported-by: Kyle Huey <m...@kylehuey.com> > > Signed-off-by: Jens Axboe <ax...@kernel.dk> > > ACK with some reservations - I suspect that we want an explicit flag > for process_vm_{read,write}v() that would force the 64bit layout for > the vector refering to the foreign process. It's not relevant for > regression fix; however, as it is these syscalls are not usable for > 32bit process trying to access memory of 64bit one - there's no way > to specify the addresses past 4G.
Independent of this fix I think we just need to explicitly prohibit cross-access.