[COMMITTED] libdw: Check there are any header bytes in str_offsets_base_off

[Mark Wielaard]

We tried to read the str_offsets header length and only then checked
if there were any bytes left. Make sure to check there are at least 4
bytes for the initial unit length.

	* libdw/libdwP.h (str_offsets_base_off): Check before initial
	unit_length read.

https://sourceware.org/bugzilla/show_bug.cgi?id=34383

Reported-by: Karan Kurani <karankurani3k@gmail.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdw/libdwP.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libdw/libdwP.h b/libdw/libdwP.h
index 628777b069da..5e1029bd2ac2 100644
--- a/libdw/libdwP.h
+++ b/libdw/libdwP.h
@@ -1282,6 +1282,8 @@ str_offsets_base_off (Dwarf *dbg, Dwarf_CU *cu)
   uint64_t unit_length;
   uint16_t version;
 
+  if (unlikely (readendp - readp < 4))
+    goto no_header;
   unit_length = read_4ubyte_unaligned_inc (dbg, readp);
   if (unlikely (unit_length == 0xffffffff))
     {
-- 
2.55.0