In NetBSD has been some PaX feature [0] implemented. (ASLR, W^X (~nxstack), mprotect restriction, veriexec, mmap randomization[2]...) [0] http://pax.grsecurity.net/docs/index.html [1] http://www.netbsd.org/~elad/recent/man/security.8.html [2] http://people.freebsd.org/~ssouhlal/testing/stackgap-20050527.diff On 10/19/11, Arnaud Lacombe <lacombar_at_gmail.com> wrote: > Hi, > > 2011/10/18 Kostik Belousov <kostikbel_at_gmail.com>: >> On Tue, Oct 18, 2011 at 01:06:27PM -0400, Arnaud Lacombe wrote: >>> Hi, >>> >>> On Tue, Oct 18, 2011 at 12:53 PM, Oliver Pinter <oliver.pntr_at_gmail.com> >>> wrote: >>> > On 10/18/11, Arnaud Lacombe <lacombar_at_gmail.com> wrote: >>> >> Hi, >>> >> >>> >> On Tue, Oct 18, 2011 at 11:44 AM, Garrett Cooper <yanegomi_at_gmail.com> >>> >> wrote: >>> >>> On Tue, 18 Oct 2011, Arnaud Lacombe wrote: >>> >>> >>> >>>> Hi, >>> >>>> >>> >>>> On Tue, Oct 18, 2011 at 5:07 AM, Kostik Belousov >>> >>>> <kostikbel_at_gmail.com> >>> >>>> wrote: >>> >>>>> >>> >>>>> On Mon, Oct 17, 2011 at 09:30:56PM +0200, Oliver Pinter wrote: >>> >>>>>> >>> >>>>>> Hi all! >>> >>>>>> >>> >>>>>> I think, it's the time to enable the nxstack feature. Any >>> >>>>>> comments, >>> >>>>>> pros, cons? >>> >>>>> >>> >>>>> I dragged the change long enough for it to miss the 9.0. >>> >>>>> After the 9.0 is released, I will flip the switch with the >>> >>>>> following >>> >>>>> change. >>> >>>>> >>> >>>>> diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c >>> >>>>> index 8455f48..926fe64 100644 >>> >>>>> --- a/sys/kern/imgact_elf.c >>> >>>>> +++ b/sys/kern/imgact_elf.c >>> >>>>> _at__at_ -118,7 +118,12 _at__at_ static int elf_legacy_coredump = 0; >>> >>>>> SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, >>> >>>>> &elf_legacy_coredump, 0, ""); >>> >>>>> >>> >>>>> -static int __elfN(nxstack) = 0; >>> >>>>> +int __elfN(nxstack) = >>> >>>>> +#if defined(__amd64__) || defined(__powerpc64__) /* both 64 and 32 >>> >>>>> bit >>> >>>>> */ >>> >>>>> >>> >>>> Why leaving 32bits x86 CPU supporting the NX feature behind ? >>> >>> >>> >>> Most likely because it was assumed that i386 doesn't fully support >>> >>> it. >>> >>> According to ye great Wikipedia, NX support didn't roll into i386 >>> >>> until >>> >>> Prescott, which was pretty late in the non-64-bit capable family of >>> >>> CPUs, >>> >>> as >>> >>> its successor -- Conroe -- was 64-bit. Intel detuned some of the >>> >>> early >>> >>> Dual >>> >>> Core Pentiums, e.g. the Yonahs to not talk 64-bit. Not sure about >>> >>> AMD. >>> >>> >>> >>> There are probably more details in binutils, gcc, etc, that I'm >>> >>> missing >>> >>> and >>> >>> Kostik can expound on. >>> >>> >>> >> NX support is advertised in the cpuid flags, just add the logic to >>> >> handle this interface. Kostik's patch is just incomplete, but he's got >>> >> a commit bit so he can commit it as-is, as he will. >>> >> >>> >> If nonexec_stack becomes the default, it should be on every CPU >>> >> supporting the feature, not just the low-hanging one. >>> >> >>> >> - Arnaud >>> >> >>> > >>> > the NX detection code already implemented in i386, but this feature >>> > required PAE: >>> > >>> yes, this is the conclusion I reached too. But this does not change >>> the fact that the VM should know about that, and this is missing from >>> Kostik's patch. I guess the first hunk should read: >>> >>> _at__at_ -118,7 +118,12 _at__at_ static int elf_legacy_coredump = 0; >>> SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, >>> &elf_legacy_coredump, 0, ""); >>> >>> -static int __elfN(nxstack) = 0; >>> +int __elfN(nxstack) = >>> +#if defined(PAE) || defined(__amd64__) || defined(__powerpc64__) /* >>> both 64 and 32 bit */ >>> + 1; >>> +#else >>> + 0; >>> +#endif >>> SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, >>> nxstack, CTLFLAG_RW, &__elfN(nxstack), 0, >>> __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": enable non-executable >>> stack"); >> >> Your patch is not right, it will cause even more user confusion. >> The presence of the PAE kernel does not imply that CPU supports nx. >> >> Below is the updated patch that turns on nxstack by default for the PAE >> kernels on NX-capable CPUs. Note that i386 usermode fully supports the >> PT_GNU_STACK annotations and cares about not enabling nx on stack pages >> unneccessary, but my main target was compat32 on amd64. >> >> The fact that nxstack is not enabled by default does not prevent >> administrator from manually enabling the feature. >> >> Since you worried so much about PAE case, I sincerely expect that you >> will test the change. Thank you in advance. >> > I will. > > Btw, NetBSD has been going down the path of system unit test, > especially of kernel/userland interfaces, and already worked-out the > framework for that. Is that something FreeBSD would be interested in ? > > Thanks, > - Arnaud > >> diff --git a/sys/i386/i386/initcpu.c b/sys/i386/i386/initcpu.c >> index c2daf54..ec77adb 100644 >> --- a/sys/i386/i386/initcpu.c >> +++ b/sys/i386/i386/initcpu.c >> _at__at_ -650,6 +650,8 _at__at_ enable_sse(void) >> #endif >> } >> >> +extern int elf32_nxstack; >> + >> void >> initializecpu(void) >> { >> _at__at_ -739,6 +741,7 _at__at_ initializecpu(void) >> msr = rdmsr(MSR_EFER) | EFER_NXE; >> wrmsr(MSR_EFER, msr); >> pg_nx = PG_NX; >> + elf32_nxstack = 1; >> } >> #endif >> break; >> diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c >> index 8455f48..926fe64 100644 >> --- a/sys/kern/imgact_elf.c >> +++ b/sys/kern/imgact_elf.c >> _at__at_ -118,7 +118,12 _at__at_ static int elf_legacy_coredump = 0; >> SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, >> &elf_legacy_coredump, 0, ""); >> >> -static int __elfN(nxstack) = 0; >> +int __elfN(nxstack) = >> +#if defined(__amd64__) || defined(__powerpc64__) /* both 64 and 32 bit */ >> + 1; >> +#else >> + 0; >> +#endif >> SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, >> nxstack, CTLFLAG_RW, &__elfN(nxstack), 0, >> __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": enable non-executable >> stack"); >> diff --git a/sys/powerpc/aim/mmu_oea64.c b/sys/powerpc/aim/mmu_oea64.c >> index 7500462..0e27351 100644 >> --- a/sys/powerpc/aim/mmu_oea64.c >> +++ b/sys/powerpc/aim/mmu_oea64.c >> _at__at_ -1445,6 +1445,8 _at__at_ moea64_uma_page_alloc(uma_zone_t zone, int bytes, >> u_int8_t *flags, int wait) >> return (void *)va; >> } >> >> +extern int elf32_nxstack; >> + >> void >> moea64_init(mmu_t mmu) >> { >> _at__at_ -1464,6 +1466,8 _at__at_ moea64_init(mmu_t mmu) >> >> uma_zone_set_allocf(moea64_mpvo_zone,moea64_uma_page_alloc); >> } >> >> + elf32_nxstack = 1; >> + >> moea64_initialized = TRUE; >> } >> >> diff --git a/sys/powerpc/booke/machdep.c b/sys/powerpc/booke/machdep.c >> index c2b5e6f..82a37e1 100644 >> --- a/sys/powerpc/booke/machdep.c >> +++ b/sys/powerpc/booke/machdep.c >> _at__at_ -192,6 +192,8 _at__at_ void print_kernel_section_addr(void); >> void print_kenv(void); >> u_int booke_init(uint32_t, uint32_t); >> >> +extern int elf32_nxstack; >> + >> static void >> cpu_e500_startup(void *dummy) >> { >> _at__at_ -227,6 +229,9 _at__at_ cpu_e500_startup(void *dummy) >> /* Set up buffers, so they can be used to read disk labels. */ >> bufinit(); >> vm_pager_bufferinit(); >> + >> + /* Cpu supports execution permissions on the pages. */ >> + elf32_nxstack = 1; >> } >> >> static char * >> >Received on Tue Oct 18 2011 - 20:37:45 UTC
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