linux-kernel - [PATCH v3 06/10] x86/sev: Avoid crossing the page boundary

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Message-ID: <56607a180717a4196738224c995fa2c16af44da2.1723807851.git.legion@kernel.org>
Date: Fri, 16 Aug 2024 15:43:56 +0200
From: Alexey Gladkov <legion@...nel.org>
To: linux-kernel@...r.kernel.org,
	linux-coco@...ts.linux.dev
Cc: "Alexey Gladkov (Intel)" <legion@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Yuan Yao <yuan.yao@...el.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Yuntao Wang <ytcoode@...il.com>,
	Kai Huang <kai.huang@...el.com>,
	Baoquan He <bhe@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Kevin Loughlin <kevinloughlin@...gle.com>,
	Nikunj A Dadhania <nikunj@....com>,
	cho@...rosoft.com,
	decui@...rosoft.com,
	John.Starks@...rosoft.com
Subject: [PATCH v3 06/10] x86/sev: Avoid crossing the page boundary

From: "Alexey Gladkov (Intel)" <legion@...nel.org>

Try to avoid crossing the page boundary to avoid side effects if the
next page belongs to another VMA.

Signed-off-by: Alexey Gladkov (Intel) <legion@...nel.org>
---
 arch/x86/coco/sev/core.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 082d61d85dfc..b0e8e4264464 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -311,17 +311,16 @@ static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,
 
 static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
 {
-	char buffer[MAX_INSN_SIZE];
-	int insn_bytes;
+	int ret;
 
-	insn_bytes = insn_fetch_from_user_inatomic(ctxt->regs, buffer);
-	if (insn_bytes == 0) {
+	ret = insn_fetch_decode_from_user_inatomic(&ctxt->insn, ctxt->regs);
+	if (ret == -EFAULT) {
 		/* Nothing could be copied */
 		ctxt->fi.vector     = X86_TRAP_PF;
 		ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
 		ctxt->fi.cr2        = ctxt->regs->ip;
 		return ES_EXCEPTION;
-	} else if (insn_bytes == -EINVAL) {
+	} else if (ret == -EINVAL) {
 		/* Effective RIP could not be calculated */
 		ctxt->fi.vector     = X86_TRAP_GP;
 		ctxt->fi.error_code = 0;
@@ -329,9 +328,6 @@ static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
 		return ES_EXCEPTION;
 	}
 
-	if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, insn_bytes))
-		return ES_DECODE_FAILED;
-
 	if (ctxt->insn.immediate.got)
 		return ES_OK;
 	else
-- 
2.45.2