Messages in this thread | | | Date | Tue, 30 Apr 2024 14:15:53 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] hardening: Refresh KCFI options, add some more |
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On Tue, Apr 30, 2024 at 10:48:36AM -0700, Kees Cook wrote: > On Tue, Apr 30, 2024 at 11:21:40AM +0200, Peter Zijlstra wrote: > > On Fri, Apr 26, 2024 at 03:29:44PM -0700, Kees Cook wrote: > > > > > - CONFIG_CFI_CLANG=y for x86 and arm64. (And disable FINEIBT since > > > it isn't as secure as straight KCFI.) > > > > Oi ? > > Same objection I always had[1]: moving the check into the destination > means attacks with control over executable memory contents can just omit > the check. > > But now that I went to go look I see 0c3e806ec0f9 ("x86/cfi: Add boot > time hash randomization") is only enabled under FINEIBT... seems better > if that were always enabled...
And FINEIBT actually can't be disabled... :|
And as it turns out CFI_CLANG doesn't work at all on v6.9...
[ 0.587220] no CFI hash found at: __call_sites+0x339a8/0x34450 ffffffffac20cef8 00 00 00 00 00 [ 0.588226] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:1182 __apply_fineibt+0x7a9/0x820 .. [ 0.619220] SMP alternatives: Something went horribly wrong trying to rewrite the CFI implementation. *hang*
-- Kees Cook
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