[PATCH 38/62] x86/sev-es: Handle instruction fetches from user-space
From: Joerg Roedel <joro@8bytes.org>
Date: 2020-02-11 13:56:23
Also in:
kvm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Joerg Roedel <redacted> When a #VC exception is triggered by user-space the instruction decoder needs to read the instruction bytes from user addresses. Enhance es_fetch_insn_byte() to safely fetch kernel and user instruction bytes. Signed-off-by: Joerg Roedel <redacted> --- arch/x86/kernel/sev-es.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 2a801919e7c0..f5bff4219f6f 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c@@ -61,13 +61,29 @@ static enum es_result es_fetch_insn_byte(struct es_em_ctxt *ctxt, unsigned int offset, char *buffer) { - char *rip = (char *)ctxt->regs->ip; - - /* More checks are needed when we boot to user-space */ - if (!check_kernel(ctxt->regs)) - return ES_UNSUPPORTED; - - buffer[offset] = rip[offset]; + if (user_mode(ctxt->regs)) { + unsigned long addr = ctxt->regs->ip + offset; + char __user *rip = (char __user *)addr; + + if (unlikely(addr >= TASK_SIZE_MAX)) + return ES_UNSUPPORTED; + + if (copy_from_user(buffer + offset, rip, 1)) { + ctxt->fi.vector = X86_TRAP_PF; + ctxt->fi.cr2 = addr; + ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER; + return ES_EXCEPTION; + } + } else { + char *rip = (char *)ctxt->regs->ip + offset; + + if (probe_kernel_read(buffer + offset, rip, 1) != 0) { + ctxt->fi.vector = X86_TRAP_PF; + ctxt->fi.cr2 = (unsigned long)rip; + ctxt->fi.error_code = X86_PF_INSTR; + return ES_EXCEPTION; + } + } return ES_OK; }
--
2.17.1