The length field could be so big that it would wrap around the next_offset.
We don't really care that length is bogus, but we don't want to use it to
calculate the next offset if it is.
Found by afl-fuzz.
Signed-off-by: Mark Wielaard <m...@klomp.org>
---
libdw/ChangeLog | 5 +++++
libdw/dwarf_nextcu.c | 5 +++++
2 files changed, 10 insertions(+)
diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 4280c55..11de763 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-22 Mark Wielaard <m...@klomp.org>
+
+ * dwarf_nextcu.c (__libdw_next_unit): Set next_off to -1 when it would
+ wrap around.
+
2018-06-18 Mark Wielaard <m...@klomp.org>
* dwarf_aggregate_size.c (array_size): New depth argument. Use
diff --git a/libdw/dwarf_nextcu.c b/libdw/dwarf_nextcu.c
index 4b394f3..be11327 100644
--- a/libdw/dwarf_nextcu.c
+++ b/libdw/dwarf_nextcu.c
@@ -278,6 +278,11 @@ __libdw_next_unit (Dwarf *dwarf, bool v4_debug_types,
Dwarf_Off off,
or with offset == 8: 2 * 8 - 4 == 12. */
*next_off = off + 2 * offset_size - 4 + length;
+ /* This means that the length field is bogus, but return the CU anyway.
+ We just won't return anything after this. */
+ if (*next_off <= off)
+ *next_off = (Dwarf_Off) -1;
+
return 0;
}
--
1.8.3.1
