On 10/4/22 10:47 AM, Nathan Chancellor wrote: > Hi Kees, > > On Mon, Oct 03, 2022 at 09:54:26PM -0700, Kees Cook wrote: >> On Mon, Oct 03, 2022 at 05:09:04PM -0700, Dave Hansen wrote: >>> On 10/3/22 16:57, Kees Cook wrote: >>>> On Thu, Sep 29, 2022 at 03:29:30PM -0700, Rick Edgecombe wrote: >>>>> Shadow stack is supported on newer AMD processors, but the kernel >>>>> implementation has not been tested on them. Prevent basic issues from >>>>> showing up for normal users by disabling shadow stack on all CPUs except >>>>> Intel until it has been tested. At which point the limitation should be >>>>> removed. >>>>> >>>>> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> >>>> So running the selftests on an AMD system is sufficient to drop this >>>> patch? >>> >>> Yes, that's enough. >>> >>> I _thought_ the AMD folks provided some tested-by's at some point in the >>> past. But, maybe I'm confusing this for one of the other shared >>> features. Either way, I'm sure no tested-by's were dropped on purpose. >>> >>> I'm sure Rick is eager to trim down his series and this would be a great >>> patch to drop. Does anyone want to make that easy for Rick? >>> >>> <hint> <hint> >> >> Hey Gustavo, Nathan, or Nick! I know y'all have some fancy AMD testing >> rigs. Got a moment to spin up this series and run the selftests? :) > > I do have access to a system with an EPYC 7513, which does have Shadow > Stack support (I can see 'shstk' in the "Flags" section of lscpu with > this series). As far as I understand it, AMD only added Shadow Stack > with Zen 3; my regular AMD test system is Zen 2 (probably should look at > procurring a Zen 3 or Zen 4 one at some point). > > I applied this series on top of 6.0 and reverted this change then booted > it on that system. After building the selftest (which did require > 'make headers_install' and a small addition to make it build beyond > that, see below), I ran it and this was the result. I am not sure if > that is expected or not but the other results seem promising for > dropping this patch. > > $ ./test_shadow_stack_64 > [INFO] new_ssp = 7f8a36c9fff8, *new_ssp = 7f8a36ca0001 > [INFO] changing ssp from 7f8a374a0ff0 to 7f8a36c9fff8 > [INFO] ssp is now 7f8a36ca0000 > [OK] Shadow stack pivot > [OK] Shadow stack faults > [INFO] Corrupting shadow stack > [INFO] Generated shadow stack violation successfully > [OK] Shadow stack violation test > [INFO] Gup read -> shstk access success > [INFO] Gup write -> shstk access success > [INFO] Violation from normal write > [INFO] Gup read -> write access success > [INFO] Violation from normal write > [INFO] Gup write -> write access success > [INFO] Cow gup write -> write access success > [OK] Shadow gup test > [INFO] Violation from shstk access > [OK] mprotect() test > [OK] Userfaultfd test > [FAIL] Alt shadow stack test The selftest is looking OK on my system (Dell PowerEdge R6515 w/ EPYC 7713). I also just pulled a fresh 6.0 kernel and applied the series including the fix Nathan mentions below. $ tools/testing/selftests/x86/test_shadow_stack_64 [INFO] new_ssp = 7f30cccc5ff8, *new_ssp = 7f30cccc6001 [INFO] changing ssp from 7f30cd4c6ff0 to 7f30cccc5ff8 [INFO] ssp is now 7f30cccc6000 [OK] Shadow stack pivot [OK] Shadow stack faults [INFO] Corrupting shadow stack [INFO] Generated shadow stack violation successfully [OK] Shadow stack violation test [INFO] Gup read -> shstk access success [INFO] Gup write -> shstk access success [INFO] Violation from normal write [INFO] Gup read -> write access success [INFO] Violation from normal write [INFO] Gup write -> write access success [INFO] Cow gup write -> write access success [OK] Shadow gup test [INFO] Violation from shstk access [OK] mprotect() test [OK] Userfaultfd test [OK] Alt shadow stack test. > > $ echo $? > 1 > > I am happy to provide any information that would be useful for exploring > this failure and test further iterations of this series as necessary. > > Cheers, > Nathan > > test_shadow_stack.c: In function ‘create_shstk’: > test_shadow_stack.c:86:70: error: ‘SHADOW_STACK_SET_TOKEN’ undeclared (first use in this function) > 86 | return (void *)syscall(__NR_map_shadow_stack, addr, SS_SIZE, SHADOW_STACK_SET_TOKEN); > | ^~~~~~~~~~~~~~~~~~~~~~ > test_shadow_stack.c:86:70: note: each undeclared identifier is reported only once for each function it appears in > test_shadow_stack.c:87:1: warning: control reaches end of non-void function [-Wreturn-type] > 87 | } > | ^ > > diff --git a/tools/testing/selftests/x86/test_shadow_stack.c b/tools/testing/selftests/x86/test_shadow_stack.c > index 22b856de5cdd..958dbb248518 100644 > --- a/tools/testing/selftests/x86/test_shadow_stack.c > +++ b/tools/testing/selftests/x86/test_shadow_stack.c > @@ -11,6 +11,7 @@ > #define _GNU_SOURCE > > #include <sys/syscall.h> > +#include <asm/mman.h> > #include <sys/mman.h> > #include <sys/stat.h> > #include <sys/wait.h>
