[PATCH v5 6/6] x86/sev-es: Propagate #GP if getting linear instruction address failed

Joerg Roedel
2021-06-14T13:53:57Z

From: Joerg Roedel <jroedel@suse.de>

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@suse.de>
---
arch/x86/kernel/sev.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 259f64be2611..2a7ddefc61a5 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -273,11 +273,18 @@ static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
int insn_bytes;

insn_bytes = insn_fetch_from_user_inatomic(ctxt->regs, buffer);
- if (insn_bytes <= 0) {
+ if (insn_bytes == 0) {
+ /* 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) {
+ /* Effective RIP could not be calculated */
+ 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