From b470757774a776e2bcbff50c7ae7f40323d10064 Mon Sep 17 00:00:00 2001
Message-Id: <b470757774a776e2bcbff50c7ae7f40323d10064@dist-git>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Thu, 7 Mar 2019 14:17:01 +0100
Subject: [PATCH] cpu: Don't access invalid memory in virCPUx86Translate
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Problem is that if there are no signatures for a CPU, then we
still allocate cpu->signatures (even though with size 0). Later,
we access cpu->signatures[0] if cpu->signatures is not NULL.

 Invalid read of size 4
    at 0x5F439D7: virCPUx86Translate (cpu_x86.c:2930)
    by 0x5F3C239: virCPUTranslate (cpu.c:927)
    by 0x57CE7A1: qemuProcessUpdateGuestCPU (qemu_process.c:5870)
    ...
  Address 0xf752d40 is 0 bytes after a block of size 0 alloc'd
    at 0x4C30EC6: calloc (vg_replace_malloc.c:711)
    by 0x5DBDE4E: virAllocN (viralloc.c:190)
    by 0x5F3E4FA: x86ModelCopySignatures (cpu_x86.c:990)
    by 0x5F3E60F: x86ModelCopy (cpu_x86.c:1008)
    by 0x5F3E7CB: x86ModelFromCPU (cpu_x86.c:1068)
    by 0x5F4397E: virCPUx86Translate (cpu_x86.c:2922)
    by 0x5F3C239: virCPUTranslate (cpu.c:927)
    by 0x57CE7A1: qemuProcessUpdateGuestCPU (qemu_process.c:5870)
    ...

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
(cherry picked from commit 62cb9c335c43a722e81ac0a1ed6e1111ba1d428b)

https://bugzilla.redhat.com/show_bug.cgi?id=1558558
https://bugzilla.redhat.com/show_bug.cgi?id=1687515

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/cpu/cpu_x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index f6844aaa0d..466c79031d 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -1021,6 +1021,9 @@ x86ModelCopySignatures(virCPUx86ModelPtr dst,
 {
     size_t i;
 
+    if (src->nsignatures == 0)
+        return 0;
+
     if (VIR_ALLOC_N(dst->signatures, src->nsignatures) < 0)
         return -1;
 
-- 
2.21.0