Commit 5e3427a7 authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov
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x86/sev-es: Handle instruction fetches from user-space 



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: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-49-joro@8bytes.org
parent d3529bb7

arch/x86/kernel/sev-es.c

+22 −9
Original line number Diff line number Diff line
@@ -232,16 +232,29 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) 
	enum es_result ret;

	int res;



	if (user_mode(ctxt->regs)) {

		res = insn_fetch_from_user(ctxt->regs, buffer);

		if (!res) {

			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;

		}



		if (!insn_decode(&ctxt->insn, ctxt->regs, buffer, res))

			return ES_DECODE_FAILED;

	} else {

		res = vc_fetch_insn_kernel(ctxt, buffer);

	if (unlikely(res == -EFAULT)) {

		if (res) {

			ctxt->fi.vector     = X86_TRAP_PF;

		ctxt->fi.error_code = 0;

			ctxt->fi.error_code = X86_PF_INSTR;

			ctxt->fi.cr2        = ctxt->regs->ip;

			return ES_EXCEPTION;

		}



		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;