[binutils-gdb] Fix gdb_bfd_section_index for special sections

[Pedro Alves <palves at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ce9c0ca18fe50e1e5a87b135032e4aeba415e2ab

commit ce9c0ca18fe50e1e5a87b135032e4aeba415e2ab
Author: Andrzej Kaczmarek <andrzej.kaczmarek@tieto.com>
Date:   Fri Mar 27 12:09:02 2015 +0000

    Fix gdb_bfd_section_index for special sections
    
    Indexes returned for special sections are off by one, i.e. with N+4
    sections last one has index N+4 returned which is outside allocated
    obstack (at the same time index N is not used at all).
    
    In worst case, if sections obstack is allocated up to end of chunk,
    writing last section data will cause buffer overrun and some data
    corruption.
    
    Here's output from Valgrind::
    
    ==14630== Invalid write of size 8
    ==14630==    at 0x551B1A: add_to_objfile_sections_full (objfiles.c:225)
    ==14630==    by 0x552768: allocate_objfile (objfiles.c:324)
    ==14630==    by 0x4E8E2E: symbol_file_add_with_addrs (symfile.c:1171)
    ==14630==    by 0x4E9453: symbol_file_add_from_bfd (symfile.c:1280)
    ==14630==    by 0x4E9453: symbol_file_add (symfile.c:1295)
    ==14630==    by 0x4E94B7: symbol_file_add_main_1 (symfile.c:1320)
    ==14630==    by 0x514246: catch_command_errors_const (main.c:398)
    ==14630==    by 0x5150AA: captured_main (main.c:1061)
    ==14630==    by 0x51123C: catch_errors (exceptions.c:240)
    ==14630==    by 0x51569A: gdb_main (main.c:1164)
    ==14630==    by 0x408824: main (gdb.c:32)
    ==14630==  Address 0x635f3b8 is 8 bytes after a block of size 4,064 alloc'd
    ==14630==    at 0x4C2ABA0: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==14630==    by 0x60F797: xmalloc (common-utils.c:41)
    ==14630==    by 0x5E787FB: _obstack_begin (obstack.c:184)
    ==14630==    by 0x552679: allocate_objfile (objfiles.c:294)
    ==14630==    by 0x4E8E2E: symbol_file_add_with_addrs (symfile.c:1171)
    ==14630==    by 0x4E9453: symbol_file_add_from_bfd (symfile.c:1280)
    ==14630==    by 0x4E9453: symbol_file_add (symfile.c:1295)
    ==14630==    by 0x4E94B7: symbol_file_add_main_1 (symfile.c:1320)
    ==14630==    by 0x514246: catch_command_errors_const (main.c:398)
    ==14630==    by 0x5150AA: captured_main (main.c:1061)
    ==14630==    by 0x51123C: catch_errors (exceptions.c:240)
    ==14630==    by 0x51569A: gdb_main (main.c:1164)
    ==14630==    by 0x408824: main (gdb.c:32)
    
    gdb/ChangeLog:
    	* gdb_bfd.c (gdb_bfd_section_index): Fix off-by-one for special
    	sections.

Diff:
---
 gdb/ChangeLog | 5 +++++
 gdb/gdb_bfd.c | 8 ++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 150b29a..3ef965c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-03-27  Andrzej Kaczmarek  <andrzej.kaczmarek@tieto.com>
+
+	* gdb_bfd.c (gdb_bfd_section_index): Fix off-by-one for special
+	sections.
+
 2015-03-26  Joel Brobecker  <brobecker@adacore.com>
 
 	* dtrace-probe.c (dtrace_process_dof_probe): Contain any
diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
index 7543dae..3f89d3a 100644
--- a/gdb/gdb_bfd.c
+++ b/gdb/gdb_bfd.c
@@ -616,13 +616,13 @@ gdb_bfd_section_index (bfd *abfd, asection *section)
   if (section == NULL)
     return -1;
   else if (section == bfd_com_section_ptr)
-    return bfd_count_sections (abfd) + 1;
+    return bfd_count_sections (abfd);
   else if (section == bfd_und_section_ptr)
-    return bfd_count_sections (abfd) + 2;
+    return bfd_count_sections (abfd) + 1;
   else if (section == bfd_abs_section_ptr)
-    return bfd_count_sections (abfd) + 3;
+    return bfd_count_sections (abfd) + 2;
   else if (section == bfd_ind_section_ptr)
-    return bfd_count_sections (abfd) + 4;
+    return bfd_count_sections (abfd) + 3;
   return section->index;
 }