From 06add254c7f3b7f6fdfe04eb028aaabe5b27a734 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 18 Feb 2020 15:29:50 -0800 Subject: [PATCH] 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 Reviewed-by: Vitaly Kuznetsov Signed-off-by: Paolo Bonzini --- arch/x86/kvm/kvm_emulate.h | 8 +++++--- arch/x86/kvm/x86.c | 12 ++++++------ 2 files changed, 11 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h index 3a66f80d7d00..f86fe6bf170d 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 f55899055467..a69f7bf020d9 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);