[binutils-gdb] gdb/dwarf: fix bound check in read_rnglist_index

[Simon Marchi]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5e4d9bbc4b4e57eacb614c38f30dac9af08cace8

commit 5e4d9bbc4b4e57eacb614c38f30dac9af08cace8
Author: Simon Marchi <simon.marchi@efficios.com>
Date:   Tue Feb 2 10:40:50 2021 -0500

    gdb/dwarf: fix bound check in read_rnglist_index
    
    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

Diff:
---
 gdb/ChangeLog     | 4 ++++
 gdb/dwarf2/read.c | 4 +++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dcbfc77761d..c71492d7a33 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2021-02-02  Simon Marchi  <simon.marchi@efficios.com>
+
+	* dwarf2/read.c (read_rnglist_index): Fix bound check.
+
 2021-02-02  Simon Marchi  <simon.marchi@efficios.com>
 
 	* dwarf2/read.c (read_loclist_index): Change complaints into
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index a9f7ce3a312..9a71329c990 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -20257,6 +20257,8 @@ 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;
 
@@ -20285,7 +20287,7 @@ 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));