From 383ec757d27652448d1511169e1133f486abf54f 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.

(cherry pick from commit f84ce13b6708801ca1d6289b7c4003e2f5a6d7f9)
Upstream-Status: Backport [master]
CVE: CVE-2017-6966

Signed-off-by: Yuanjie Huang <yuanjie.huang@windriver.com>
---
 binutils/ChangeLog |  10 +++++
 binutils/readelf.c | 109 +++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 94 insertions(+), 25 deletions(-)

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index e789a3b99b..bd63c8a0d8 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,5 +1,15 @@
 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.
+
+2017-02-13  Nick Clifton  <nickc@redhat.com>
+
 	PR binutils/21137
 	* readelf.c (target_specific_reloc_handling): Add end parameter.
 	Check for buffer overflow before writing relocated values.
diff --git a/binutils/readelf.c b/binutils/readelf.c
index 8cdaae3b8c..7c158c6342 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -11580,15 +11580,27 @@ 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)
     {
@@ -11597,6 +11609,12 @@ 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 */
@@ -11604,7 +11622,12 @@ 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 */
@@ -11629,16 +11652,21 @@ 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;
@@ -11658,13 +11686,24 @@ 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)
@@ -11672,15 +11711,20 @@ 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;
@@ -11700,12 +11744,24 @@ 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.  */
@@ -12345,7 +12401,7 @@ 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;
@@ -12441,6 +12497,9 @@ 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)
 	{
-- 
2.11.0

