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[v2,53/63] KVM: x86: Use struct_group() to zero decode cache

Message ID 20210818060533.3569517-54-keescook@chromium.org
State New
Headers show
Series Introduce strict memcpy() bounds checking | expand

Commit Message

Kees Cook Aug. 18, 2021, 6:05 a.m. UTC 
In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct x86_emulate_ctxt that should
be initialized to zero.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/kvm/emulate.c     |  3 +--
 arch/x86/kvm/kvm_emulate.h | 19 +++++++++++--------
 2 files changed, 12 insertions(+), 10 deletions(-)
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Patch

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 2837110e66ed..2608a047e769 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5377,8 +5377,7 @@  static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop)
 
 void init_decode_cache(struct x86_emulate_ctxt *ctxt)
 {
-	memset(&ctxt->rip_relative, 0,
-	       (void *)&ctxt->modrm - (void *)&ctxt->rip_relative);
+	memset(&ctxt->decode_cache, 0, sizeof(ctxt->decode_cache));
 
 	ctxt->io_read.pos = 0;
 	ctxt->io_read.end = 0;
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 68b420289d7e..9b8afcb8ad39 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -341,14 +341,17 @@  struct x86_emulate_ctxt {
 	 * the rest are initialized unconditionally in x86_decode_insn
 	 * or elsewhere
 	 */
-	bool rip_relative;
-	u8 rex_prefix;
-	u8 lock_prefix;
-	u8 rep_prefix;
-	/* bitmaps of registers in _regs[] that can be read */
-	u32 regs_valid;
-	/* bitmaps of registers in _regs[] that have been written */
-	u32 regs_dirty;
+	struct_group(decode_cache,
+		bool rip_relative;
+		u8 rex_prefix;
+		u8 lock_prefix;
+		u8 rep_prefix;
+		/* bitmaps of registers in _regs[] that can be read */
+		u32 regs_valid;
+		/* bitmaps of registers in _regs[] that have been written */
+		u32 regs_dirty;
+	);
+
 	/* modrm */
 	u8 modrm;
 	u8 modrm_mod;