x86/sev: Check for user-space IOIO pointing to kernel space
[ 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. ]
BUG=b/309804303
TEST=presubmit
RELEASE_NOTE=Fixes CVE-2023-46813.
SOURCE=UPSTREAM(63e44bc52047)
Fixes: 597cfe48212a ("x86/boot/compressed/64: Setup a GHCB-based VC Exception handler")
Reported-by: Tom Dohrmann <erbse.13@gmx.de>
Change-Id: Ic0f52ed445d6410f059add5c5f0b3a061cb77d69
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/61355
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index c9314f4..eee87aa 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -108,6 +108,11 @@
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 eada677..c94ce93 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -620,6 +620,23 @@
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,
@@ -627,7 +644,12 @@
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);
@@ -648,7 +670,12 @@
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);
