[PATCH v2 33/39] x86/cpufeatures: Limit shadow stack to Intel CPUs
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: 2022-09-29 22:37:34
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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@intel.com> --- v1: - New patch. arch/x86/kernel/cpu/common.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d7415bb556b2..f7cacc5698d5 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c@@ -606,6 +606,14 @@ static __always_inline void setup_cet(struct cpuinfo_x86 *c) if (!kernel_ibt && !user_shstk) return; + /* + * Shadow stack is supported on AMD processors, but has not been + * tested. Only support it on Intel processors until this is done. + * At which point, this vendor check should be removed. + */ + if (c->x86_vendor != X86_VENDOR_INTEL) + setup_clear_cpu_cap(X86_FEATURE_SHSTK); + if (kernel_ibt) msr = CET_ENDBR_EN;
--
2.17.1