[PATCH v2 8/8] x86/sev-es: Propagate #GP if getting linear instruction address failed

Joerg Roedel
Wed, 19 May 2021 13:52:51 -0000

When an instruction is fetched from user-space, segmentation needs to
be taken into account. This means that getting the linear address of
an instruction can fail. Hardware would raise a #GP
exception in that case, but the #VC exception handler would emulate it
as a page-fault.

The insn_fetch_from_user*() functions now provide the relevant
information in case of an failure. Use that and propagate a #GP when
the linear address of an instruction to fetch could not be calculated.

Signed-off-by: Joerg Roedel <jroedel at suse.de>
---
 arch/x86/kernel/sev.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 1edb6cd5e308..4736290361e4 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -261,11 +261,16 @@ static enum es_result __vc_decode_user_insn(struct
es_em_ctxt *ctxt)
 	int insn_bytes = 0, res;

 	res = insn_fetch_from_user_inatomic(ctxt->regs, buffer, &insn_bytes);
-	if (res) {
+	if (res == -EFAULT) {
 		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 (res == -EINVAL) {
+		ctxt->fi.vector     = X86_TRAP_GP;
+		ctxt->fi.error_code = 0;
+		ctxt->fi.cr2        = 0;
+		return ES_EXCEPTION;
 	}

 	if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer,
insn_bytes))
--
2.31.1