5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Joerg Roedel <jroedel@xxxxxxx>
Upstream commit: 63e44bc52047f182601e7817da969a105aa1f721
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@xxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/boot/compressed/sev-es.c | 5 +++++
arch/x86/kernel/sev-es-shared.c | 31 +++++++++++++++++++++++++++++--
2 files changed, 34 insertions(+), 2 deletions(-)
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -111,6 +111,11 @@ static enum es_result vc_ioio_check(stru
return ES_OK;
}
+static bool fault_in_kernel_space(unsigned long address)
+{
+ return false;
+}
+
#undef __init
#undef __pa
#define __init
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -217,6 +217,23 @@ fail:
asm volatile("hlt\n");
}
+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,
@@ -224,7 +241,12 @@ static enum es_result vc_insn_string_rea
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);
@@ -245,7 +267,12 @@ static enum es_result vc_insn_string_wri
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);
