From: Joerg Roedel <jroedel@xxxxxxx>
When a #VC exception is triggered by user-space the instruction decoder
needs to read the instruction bytes from user addresses. Enhance
vc_decode_insn() to safely fetch kernel and user instructions.
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
arch/x86/kernel/sev-es.c | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 226ab0c57a09..79a71d14a1fc 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -114,17 +114,30 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
enum es_result ret;
int res;
- res = vc_fetch_insn_kernel(ctxt, buffer);
- if (unlikely(res == -EFAULT)) {
- ctxt->fi.vector = X86_TRAP_PF;
- ctxt->fi.error_code = 0;
- ctxt->fi.cr2 = ctxt->regs->ip;
- return ES_EXCEPTION;
+ if (!user_mode(ctxt->regs)) {
+ res = vc_fetch_insn_kernel(ctxt, buffer);
+ if (unlikely(res == -EFAULT)) {
+ ctxt->fi.vector = X86_TRAP_PF;
+ ctxt->fi.error_code = 0;
+ ctxt->fi.cr2 = ctxt->regs->ip;
+ return ES_EXCEPTION;
+ }
+
+ insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1);
+ insn_get_length(&ctxt->insn);
+ } else {
+ res = insn_fetch_from_user(ctxt->regs, buffer);
+ if (res == 0) {
+ ctxt->fi.vector = X86_TRAP_PF;
+ ctxt->fi.cr2 = ctxt->regs->ip;
+ ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
+ return ES_EXCEPTION;
+ }
+
+ if (!insn_decode(ctxt->regs, &ctxt->insn, buffer, res))
+ return ES_DECODE_FAILED;
}
- insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1);
- insn_get_length(&ctxt->insn);
-
ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
return ret;
--
2.17.1
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
