From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Tue, 18 Feb 2020 23:29:50 +0000 (-0800)
Subject: KVM: x86: Shrink the usercopy region of the emulation context
X-Git-Tag: v5.10.7~2921^2~142
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=06add254c7f3b7f6fdfe04eb028aaabe5b27a734;p=platform%2Fkernel%2Flinux-rpi.git

KVM: x86: Shrink the usercopy region of the emulation context

Shuffle a few operand structs to the end of struct x86_emulate_ctxt and
update the cache creation to whitelist only the region of the emulation
context that is expected to be copied to/from user memory, e.g. the
instruction operands, registers, and fetch/io/mem caches.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 3a66f80..f86fe6b 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -334,9 +334,6 @@ struct x86_emulate_ctxt {
 	u8 intercept;
 	u8 op_bytes;
 	u8 ad_bytes;
-	struct operand src;
-	struct operand src2;
-	struct operand dst;
 	union {
 		int (*execute)(struct x86_emulate_ctxt *ctxt);
 		fastop_t fop;
@@ -364,6 +361,11 @@ struct x86_emulate_ctxt {
 	u8 seg_override;
 	u64 d;
 	unsigned long _eip;
+
+	/* Here begins the usercopy section. */
+	struct operand src;
+	struct operand src2;
+	struct operand dst;
 	struct operand memop;
 	/* Fields above regs are cleared together. */
 	unsigned long _regs[NR_VCPU_REGS];
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f558990..a69f7bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -235,13 +235,13 @@ static struct kmem_cache *x86_emulator_cache;
 
 static struct kmem_cache *kvm_alloc_emulator_cache(void)
 {
-	return kmem_cache_create_usercopy("x86_emulator",
-					  sizeof(struct x86_emulate_ctxt),
+	unsigned int useroffset = offsetof(struct x86_emulate_ctxt, src);
+	unsigned int size = sizeof(struct x86_emulate_ctxt);
+
+	return kmem_cache_create_usercopy("x86_emulator", size,
 					  __alignof__(struct x86_emulate_ctxt),
-					  SLAB_ACCOUNT,
-					  0,
-					  sizeof(struct x86_emulate_ctxt),
-					  NULL);
+					  SLAB_ACCOUNT, useroffset,
+					  size - useroffset, NULL);
 }
 
 static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);