Fix gdb_bfd_section_index() for special sections
Commit Message
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 return value for special
sections
---
gdb/gdb_bfd.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
Comments
On 03/17/2015 02:26 PM, Andrzej Kaczmarek wrote:
> 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.
Regression tested on x86_64 Fedora 20, and pushed.
Thanks,
@@ -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;
}