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[SRU,Lunar,3/3] x86/sev: Check for user-space IOIO pointing to kernel space

Message ID 20231201131601.1146971-7-magali.lemes@canonical.com
State New
Headers show
Series [SRU,Jammy,1/3] x86/sev: Disable MMIO emulation from user mode | expand

Commit Message

Magali Lemes Dec. 1, 2023, 1:16 p.m. UTC 
From: Joerg Roedel <jroedel@suse.de>

Check the memory operand of INS/OUTS before emulating the instruction.
The #VC exception can get raised from user-space, but the memory operand
can be manipulated to access kernel memory before the emulation actually
begins and after the exception handler has run.

  [ bp: Massage commit message. ]

Fixes: 597cfe48212a ("x86/boot/compressed/64: Setup a GHCB-based VC Exception handler")
Reported-by: Tom Dohrmann <erbse.13@gmx.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
(cherry picked from commit 63e44bc52047f182601e7817da969a105aa1f721)
CVE-2023-46813
Signed-off-by: Magali Lemes <magali.lemes@canonical.com>
---
 arch/x86/boot/compressed/sev.c |  5 +++++
 arch/x86/kernel/sev-shared.c   | 31 +++++++++++++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index b9b8ff3fe8e9..9c91cc40f456 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -108,6 +108,11 @@  static enum es_result vc_ioio_check(struct es_em_ctxt *ctxt, u16 port, size_t si
 	return ES_OK;
 }
 
+static bool fault_in_kernel_space(unsigned long address)
+{
+	return false;
+}
+
 #undef __init
 #undef __pa
 #define __init
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index ebb24c09ffd6..8abd18811238 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -589,6 +589,23 @@  void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
 	sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
 }
 
+static enum es_result vc_insn_string_check(struct es_em_ctxt *ctxt,
+					   unsigned long address,
+					   bool write)
+{
+	if (user_mode(ctxt->regs) && fault_in_kernel_space(address)) {
+		ctxt->fi.vector     = X86_TRAP_PF;
+		ctxt->fi.error_code = X86_PF_USER;
+		ctxt->fi.cr2        = address;
+		if (write)
+			ctxt->fi.error_code |= X86_PF_WRITE;
+
+		return ES_EXCEPTION;
+	}
+
+	return ES_OK;
+}
+
 static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
 					  void *src, char *buf,
 					  unsigned int data_size,
@@ -596,7 +613,12 @@  static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
 					  bool backwards)
 {
 	int i, b = backwards ? -1 : 1;
-	enum es_result ret = ES_OK;
+	unsigned long address = (unsigned long)src;
+	enum es_result ret;
+
+	ret = vc_insn_string_check(ctxt, address, false);
+	if (ret != ES_OK)
+		return ret;
 
 	for (i = 0; i < count; i++) {
 		void *s = src + (i * data_size * b);
@@ -617,7 +639,12 @@  static enum es_result vc_insn_string_write(struct es_em_ctxt *ctxt,
 					   bool backwards)
 {
 	int i, s = backwards ? -1 : 1;
-	enum es_result ret = ES_OK;
+	unsigned long address = (unsigned long)dst;
+	enum es_result ret;
+
+	ret = vc_insn_string_check(ctxt, address, true);
+	if (ret != ES_OK)
+		return ret;
 
 	for (i = 0; i < count; i++) {
 		void *d = dst + (i * data_size * s);