On Fri, Dec 02, 2016 at 01:32:24PM -0800, Kees Cook wrote: > On Thu, Dec 1, 2016 at 8:22 PM, Michael Ellerman <m...@ellerman.id.au> wrote: > > This adds two tests, to check that a read or write to LIST_POISON1 and > > ZERO_SIZE_PTR are blocked. > > > > The default values for both (256 and 16) typically fall in the range > > of valid user space addresses. However in general mmap_min_addr is 64K, > > which prevents user space from mapping anything at those addresses. > > > > However it's feasible that an attacker will be able to find a way to > > cause an access at an offset from either value, and if that offset is > > greater than 64K then they can access user space again. > > > > To simulate that case, in the test we create a user mapping at > > approximately mmap_min_addr, and offset the pointer by that amount. This > > gives the test the greatest chance of failing (ie. an access > > succeeding). We don't actually use mmap_min_addr, because that would > > require exporting it to modules, instead we use the default value at > > compile time as a reasonable approximation. > > > > Signed-off-by: Michael Ellerman <m...@ellerman.id.au> > > Thanks for this! I like it. :) > > Acked-by: Kees Cook <keesc...@chromium.org> > > Greg, can you take this into your tree?
Sure, will do so on Monday. thanks, greg k-h
