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# DP: Fix PR binutils/21139, read-after-free error in readelf.
From f84ce13b6708801ca1d6289b7c4003e2f5a6d7f9 Mon Sep 17 00:00:00 2001
From: Nick Clifton <nickc@redhat.com>
Date: Mon, 13 Feb 2017 14:03:22 +0000
Subject: [PATCH] Fix read-after-free error in readelf when processing
multiple, relocated sections in an MSP430 binary.
PR binutils/21139
* readelf.c (target_specific_reloc_handling): Add num_syms
parameter. Check for symbol table overflow before accessing
symbol value. If reloc pointer is NULL, discard all saved state.
(apply_relocations): Pass num_syms to target_specific_reloc_handling.
Call target_specific_reloc_handling with a NULL reloc pointer
after processing all of the relocs.
---
binutils/ChangeLog | 10 +++++
binutils/readelf.c | 109 +++++++++++++++++++++++++++++++++++++++++------------
2 files changed, 94 insertions(+), 25 deletions(-)
2017-02-13 Nick Clifton <nickc@redhat.com>
PR binutils/21139
* readelf.c (target_specific_reloc_handling): Add num_syms
parameter. Check for symbol table overflow before accessing
symbol value. If reloc pointer is NULL, discard all saved state.
(apply_relocations): Pass num_syms to target_specific_reloc_handling.
Call target_specific_reloc_handling with a NULL reloc pointer
after processing all of the relocs.
diff --git a/binutils/readelf.c b/binutils/readelf.c
index e474f27..de961c4 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -11586,15 +11586,27 @@ process_syminfo (FILE * file ATTRIBUTE_UNUSED)
/* Check to see if the given reloc needs to be handled in a target specific
manner. If so then process the reloc and return TRUE otherwise return
- FALSE. */
+ FALSE.
+
+ If called with reloc == NULL, then this is a signal that reloc processing
+ for the current section has finished, and any saved state should be
+ discarded. */
static bfd_boolean
target_specific_reloc_handling (Elf_Internal_Rela * reloc,
unsigned char * start,
unsigned char * end,
- Elf_Internal_Sym * symtab)
+ Elf_Internal_Sym * symtab,
+ unsigned long num_syms)
{
- unsigned int reloc_type = get_reloc_type (reloc->r_info);
+ unsigned int reloc_type = 0;
+ unsigned long sym_index = 0;
+
+ if (reloc)
+ {
+ reloc_type = get_reloc_type (reloc->r_info);
+ sym_index = get_reloc_symindex (reloc->r_info);
+ }
switch (elf_header.e_machine)
{
@@ -11603,6 +11615,12 @@ target_specific_reloc_handling (Elf_Internal_Rela * reloc,
{
static Elf_Internal_Sym * saved_sym = NULL;
+ if (reloc == NULL)
+ {
+ saved_sym = NULL;
+ return TRUE;
+ }
+
switch (reloc_type)
{
case 10: /* R_MSP430_SYM_DIFF */
@@ -11610,7 +11628,12 @@ target_specific_reloc_handling (Elf_Internal_Rela * reloc,
break;
/* Fall through. */
case 21: /* R_MSP430X_SYM_DIFF */
- saved_sym = symtab + get_reloc_symindex (reloc->r_info);
+ /* PR 21139. */
+ if (sym_index >= num_syms)
+ error (_("MSP430 SYM_DIFF reloc contains invalid symbol index %lu\n"),
+ sym_index);
+ else
+ saved_sym = symtab + sym_index;
return TRUE;
case 1: /* R_MSP430_32 or R_MSP430_ABS32 */
@@ -11635,16 +11658,21 @@ target_specific_reloc_handling (Elf_Internal_Rela * reloc,
int reloc_size = reloc_type == 1 ? 4 : 2;
bfd_vma value;
- value = reloc->r_addend
- + (symtab[get_reloc_symindex (reloc->r_info)].st_value
- - saved_sym->st_value);
-
- if (start + reloc->r_offset + reloc_size >= end)
- /* PR 21137 */
- error (_("MSP430 sym diff reloc writes past end of section (%p vs %p)\n"),
- start + reloc->r_offset + reloc_size, end);
+ if (sym_index >= num_syms)
+ error (_("MSP430 reloc contains invalid symbol index %lu\n"),
+ sym_index);
else
- byte_put (start + reloc->r_offset, value, reloc_size);
+ {
+ value = reloc->r_addend + (symtab[sym_index].st_value
+ - saved_sym->st_value);
+
+ if (start + reloc->r_offset + reloc_size >= end)
+ /* PR 21137 */
+ error (_("MSP430 sym diff reloc writes past end of section (%p vs %p)\n"),
+ start + reloc->r_offset + reloc_size, end);
+ else
+ byte_put (start + reloc->r_offset, value, reloc_size);
+ }
saved_sym = NULL;
return TRUE;
@@ -11664,13 +11692,24 @@ target_specific_reloc_handling (Elf_Internal_Rela * reloc,
{
static Elf_Internal_Sym * saved_sym = NULL;
+ if (reloc == NULL)
+ {
+ saved_sym = NULL;
+ return TRUE;
+ }
+
switch (reloc_type)
{
case 34: /* R_MN10300_ALIGN */
return TRUE;
case 33: /* R_MN10300_SYM_DIFF */
- saved_sym = symtab + get_reloc_symindex (reloc->r_info);
+ if (sym_index >= num_syms)
+ error (_("MN10300_SYM_DIFF reloc contains invalid symbol index %lu\n"),
+ sym_index);
+ else
+ saved_sym = symtab + sym_index;
return TRUE;
+
case 1: /* R_MN10300_32 */
case 2: /* R_MN10300_16 */
if (saved_sym != NULL)
@@ -11678,15 +11717,20 @@ target_specific_reloc_handling (Elf_Internal_Rela * reloc,
int reloc_size = reloc_type == 1 ? 4 : 2;
bfd_vma value;
- value = reloc->r_addend
- + (symtab[get_reloc_symindex (reloc->r_info)].st_value
- - saved_sym->st_value);
-
- if (start + reloc->r_offset + reloc_size >= end)
- error (_("MN10300 sym diff reloc writes past end of section (%p vs %p)\n"),
- start + reloc->r_offset + reloc_size, end);
+ if (sym_index >= num_syms)
+ error (_("MN10300 reloc contains invalid symbol index %lu\n"),
+ sym_index);
else
- byte_put (start + reloc->r_offset, value, reloc_size);
+ {
+ value = reloc->r_addend + (symtab[sym_index].st_value
+ - saved_sym->st_value);
+
+ if (start + reloc->r_offset + reloc_size >= end)
+ error (_("MN10300 sym diff reloc writes past end of section (%p vs %p)\n"),
+ start + reloc->r_offset + reloc_size, end);
+ else
+ byte_put (start + reloc->r_offset, value, reloc_size);
+ }
saved_sym = NULL;
return TRUE;
@@ -11706,12 +11750,24 @@ target_specific_reloc_handling (Elf_Internal_Rela * reloc,
static bfd_vma saved_sym2 = 0;
static bfd_vma value;
+ if (reloc == NULL)
+ {
+ saved_sym1 = saved_sym2 = 0;
+ return TRUE;
+ }
+
switch (reloc_type)
{
case 0x80: /* R_RL78_SYM. */
saved_sym1 = saved_sym2;
- saved_sym2 = symtab[get_reloc_symindex (reloc->r_info)].st_value;
- saved_sym2 += reloc->r_addend;
+ if (sym_index >= num_syms)
+ error (_("RL78_SYM reloc contains invalid symbol index %lu\n"),
+ sym_index);
+ else
+ {
+ saved_sym2 = symtab[sym_index].st_value;
+ saved_sym2 += reloc->r_addend;
+ }
return TRUE;
case 0x83: /* R_RL78_OPsub. */
@@ -12360,7 +12416,7 @@ apply_relocations (void * file,
reloc_type = get_reloc_type (rp->r_info);
- if (target_specific_reloc_handling (rp, start, end, symtab))
+ if (target_specific_reloc_handling (rp, start, end, symtab, num_syms))
continue;
else if (is_none_reloc (reloc_type))
continue;
@@ -12456,6 +12512,9 @@ apply_relocations (void * file,
}
free (symtab);
+ /* Let the target specific reloc processing code know that
+ we have finished with these relocs. */
+ target_specific_reloc_handling (NULL, NULL, NULL, NULL, 0);
if (relocs_return)
{
--
2.9.3
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