[COMMITTED] libdw: Check there is .debug_info/types section data in __libdw_offdie.

[Mark Wielaard <mark@klomp.org>]

If a Dwarf_Die was requested from an offset into a section data that
didn't exist we would crash. Crashing is bad even if given bad input.
Just return an error in that case.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdw/ChangeLog      | 4 ++++
 libdw/dwarf_offdie.c | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index eb1cb709..97155de1 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,7 @@
+2017-12-28  Mark Wielaard  <mark@klomp.org>
+
+	* dwarf_offdie.c (__libdw_offdie): Check sectiondata exists.
+
 2017-05-09  Ulf Hermann  <ulf.hermann@qt.io>
 	    Mark Wielaard  <mark@klomp.org>
 
diff --git a/libdw/dwarf_offdie.c b/libdw/dwarf_offdie.c
index 15f55c22..883720de 100644
--- a/libdw/dwarf_offdie.c
+++ b/libdw/dwarf_offdie.c
@@ -1,5 +1,5 @@
 /* Return DIE at given offset.
-   Copyright (C) 2002-2010 Red Hat, Inc.
+   Copyright (C) 2002-2010, 2017 Red Hat, Inc.
    This file is part of elfutils.
    Written by Ulrich Drepper <drepper@redhat.com>, 2002.
 
@@ -45,7 +45,7 @@ __libdw_offdie (Dwarf *dbg, Dwarf_Off offset, Dwarf_Die *result,
 
   Elf_Data *const data = dbg->sectiondata[debug_types ? IDX_debug_types
 					  : IDX_debug_info];
-  if (offset >= data->d_size)
+  if (data == NULL || offset >= data->d_size)
     {
       __libdw_seterrno (DWARF_E_INVALID_DWARF);
       return NULL;
-- 
2.14.3