[PATCH 02/13] gdb/dwarf: fix bound check in read_rnglist_index

Simon Marchi via Gdb-patches
2021-01-20T05:39:31Z

From: Simon Marchi <simon.marchi@efficios.com>

I think this check in read_rnglist_index is wrong:

/* Validate that reading won't go beyond the end of the section. */
if (start_offset + cu->header.offset_size > rnglist_base + section->size)
error (_("Reading DW_FORM_rnglistx index beyond end of"
".debug_rnglists section [in module %s]"),
objfile_name (objfile));

The addition `rnglist_base + section->size` doesn't make sense.
rnglist_base is an offset into `section`, so it doesn't make sense to
add it to `section`'s size. `start_offset` also is an offset into
`section`, so we should just compare it to just `section->size`.

gdb/ChangeLog:

* dwarf2/read.c (read_rnglist_index): Fix bound check.

Change-Id: If0ff7c73f4f80f79aac447518f4e8f131f2db8f2
---
gdb/dwarf2/read.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 2b76ed001616..f3bc35644c8a 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -20229,6 +20229,8 @@ read_rnglist_index (struct dwarf2_cu *cu, ULONGEST rnglist_index,
: RNGLIST_HEADER_SIZE64);
ULONGEST rnglist_base =
(cu->dwo_unit != nullptr) ? rnglist_header_size : cu->ranges_base;
+
+ /* Offset in .debug_rnglists of the offset for RNGLIST_INDEX. */
ULONGEST start_offset =
rnglist_base + rnglist_index * cu->header.offset_size;

@@ -20257,7 +20259,7 @@ read_rnglist_index (struct dwarf2_cu *cu, ULONGEST rnglist_index,
objfile_name (objfile));

/* Validate that reading won't go beyond the end of the section. */
- if (start_offset + cu->header.offset_size > rnglist_base + section->size)
+ if (start_offset + cu->header.offset_size > section->size)
error (_("Reading DW_FORM_rnglistx index beyond end of"
".debug_rnglists section [in module %s]"),
objfile_name (objfile));
--
2.30.0