PR28306, segfault in _bfd_mips_elf_reloc_unshuffle

Access to section data during relocation processing should be bounds
checked, as it is in bfd_perform_relocation.  bfd_perform_relocation
does these checks after any special_function is called.  So a reloc
special_function needs to do its own bounds checking before accessing
section data.  This patch adds many such checks to the mips backend.

Checking mips relocs is not without some difficulty.  See the comment
in _bfd_mips_reloc_offset_in_range.  In a multitple reloc sequence
applied to the same location, relocs that may appear somewhere other
than the last one of the sequence need to be treated specially since
they apply to the addend for the next relocation rather than the
section contents.  If the addend is in the section then it needs to be
checked but not when the addend is in the reloc.  check_inplace
handles this situation.  _bfd_mips_reloc_offset_in_range with
check_shuffle handles the case where contents are shuffled before
applying the relocation.

	PR 28306
	* elf32-mips.c (_bfd_mips_elf32_gprel16_reloc): Check reloc
	address using _bfd_mips_reloc_offset_in_range.
	(gprel32_with_gp, mips16_gprel_reloc): Likewise.
	* elf64-mips.c (mips_elf64_gprel32_reloc): Likewise.
	(mips16_gprel_reloc): Likewise.
	* elfn32-mips.c (mips16_gprel_reloc): Likewise.
	(gprel32_with_gp): Check reloc address using
	bfd_reloc_offset_in_range.
	* elfxx-mips.h (enum reloc_check): Define.
	(_bfd_mips_reloc_offset_in_range): Declare.
	* elfxx-mips.c (needs_shuffle): New function.
	(_bfd_mips_elf_reloc_unshuffle, _bfd_mips_elf_reloc_shuffle): Use it.
	(_bfd_mips_reloc_offset_in_range): New function.
	(_bfd_mips_elf_gprel16_with_gp): Move reloc address checks to
	partial_inplace handling.  Use bfd_reloc_offset_in_range.
	(_bfd_mips_elf_lo16_reloc): Check reloc address using
	bfd_reloc_offset_in_range.
	(_bfd_mips_elf_generic_reloc): Check reloc address using
	_bfd_mips_reloc_offset_in_range.
	(mips_elf_calculate_relocation): Check reloc address before calling
	mips_elf_nullify_got_load.
	(_bfd_mips_elf_check_relocs): Likewise.
	(mips_elf_read_rel_addend): Add sec param, check reloc address
	before reading.  Adjust callers.
	(mips_elf_add_lo16_rel_addend): Add sec param, adjust callers.

5 files changed, 96 insertions, 22 deletions

diff --git a/bfd/elf32-mips.c b/bfd/elf32-mips.c
index 3f92df6..be28d1a 100644
--- a/bfd/elf32-mips.c
+++ b/bfd/elf32-mips.c
@@ -1790,6 +1790,10 @@ _bfd_mips_elf32_gprel16_reloc (bfd *abfd, arelent *reloc_entry,
   if (ret != bfd_reloc_ok)
     return ret;
 
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					check_shuffle))
+    return bfd_reloc_outofrange;
+
   location = (bfd_byte *) data + reloc_entry->address;
   _bfd_mips_elf_reloc_unshuffle (abfd, reloc_entry->howto->type, false,
 				 location);
@@ -1857,7 +1861,8 @@ gprel32_with_gp (bfd *abfd, asymbol *symbol, arelent *reloc_entry,
   relocation += symbol->section->output_section->vma;
   relocation += symbol->section->output_offset;
 
-  if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					check_inplace))
     return bfd_reloc_outofrange;
 
   /* Set val to the offset into the section or symbol.  */
@@ -1956,6 +1961,10 @@ mips16_gprel_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
   if (ret != bfd_reloc_ok)
     return ret;
 
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					check_shuffle))
+    return bfd_reloc_outofrange;
+
   location = (bfd_byte *) data + reloc_entry->address;
   _bfd_mips_elf_reloc_unshuffle (abfd, reloc_entry->howto->type, false,
 				 location);
diff --git a/bfd/elf64-mips.c b/bfd/elf64-mips.c
index e3ee0b9..419d9bc 100644
--- a/bfd/elf64-mips.c
+++ b/bfd/elf64-mips.c
@@ -3580,7 +3580,8 @@ mips_elf64_gprel32_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
   relocation += symbol->section->output_section->vma;
   relocation += symbol->section->output_offset;
 
-  if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					check_inplace))
     return bfd_reloc_outofrange;
 
   /* Set val to the offset into the section or symbol.  */
@@ -3661,6 +3662,10 @@ mips16_gprel_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
   if (ret != bfd_reloc_ok)
     return ret;
 
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					check_shuffle))
+    return bfd_reloc_outofrange;
+
   location = (bfd_byte *) data + reloc_entry->address;
   _bfd_mips_elf_reloc_unshuffle (abfd, reloc_entry->howto->type, false,
 				 location);
diff --git a/bfd/elfn32-mips.c b/bfd/elfn32-mips.c
index ac604ed..d222d1a 100644
--- a/bfd/elfn32-mips.c
+++ b/bfd/elfn32-mips.c
@@ -3411,7 +3411,8 @@ gprel32_with_gp (bfd *abfd, asymbol *symbol, arelent *reloc_entry,
   relocation += symbol->section->output_section->vma;
   relocation += symbol->section->output_offset;
 
-  if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
+  if (!bfd_reloc_offset_in_range (reloc_entry->howto, abfd, input_section,
+				  reloc_entry->address))
     return bfd_reloc_outofrange;
 
   if (reloc_entry->howto->src_mask == 0)
@@ -3491,6 +3492,10 @@ mips16_gprel_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
   if (ret != bfd_reloc_ok)
     return ret;
 
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					check_shuffle))
+    return bfd_reloc_outofrange;
+
   location = (bfd_byte *) data + reloc_entry->address;
   _bfd_mips_elf_reloc_unshuffle (abfd, reloc_entry->howto->type, false,
 				 location);
diff --git a/bfd/elfxx-mips.c b/bfd/elfxx-mips.c
index 932167c..618fb43 100644
--- a/bfd/elfxx-mips.c
+++ b/bfd/elfxx-mips.c
@@ -2346,13 +2346,19 @@ tls_gottprel_reloc_p (unsigned int r_type)
 	  || r_type == R_MICROMIPS_TLS_GOTTPREL);
 }
 
+static inline bool
+needs_shuffle (int r_type)
+{
+  return mips16_reloc_p (r_type) || micromips_reloc_shuffle_p (r_type);
+}
+
 void
 _bfd_mips_elf_reloc_unshuffle (bfd *abfd, int r_type,
 			       bool jal_shuffle, bfd_byte *data)
 {
   bfd_vma first, second, val;
 
-  if (!mips16_reloc_p (r_type) && !micromips_reloc_shuffle_p (r_type))
+  if (!needs_shuffle (r_type))
     return;
 
   /* Pick up the first and second halfwords of the instruction.  */
@@ -2375,7 +2381,7 @@ _bfd_mips_elf_reloc_shuffle (bfd *abfd, int r_type,
 {
   bfd_vma first, second, val;
 
-  if (!mips16_reloc_p (r_type) && !micromips_reloc_shuffle_p (r_type))
+  if (!needs_shuffle (r_type))
     return;
 
   val = bfd_get_32 (abfd, data);
@@ -2399,6 +2405,32 @@ _bfd_mips_elf_reloc_shuffle (bfd *abfd, int r_type,
   bfd_put_16 (abfd, first, data);
 }
 
+/* Perform reloc offset checking.
+   We can only use bfd_reloc_offset_in_range, which takes into account
+   the size of the field being relocated, when section contents will
+   be accessed because mips object files may use relocations that seem
+   to access beyond section limits.
+   gas/testsuite/gas/mips/dla-reloc.s is an example that puts
+   R_MIPS_SUB, a 64-bit relocation, on the last instruction in the
+   section.  The R_MIPS_SUB applies to the addend for the next reloc
+   rather than the section contents.
+
+   CHECK is CHECK_STD for the standard bfd_reloc_offset_in_range check,
+   CHECK_INPLACE to only check partial_inplace relocs, and
+   CHECK_SHUFFLE to only check relocs that shuffle/unshuffle.  */
+
+bool
+_bfd_mips_reloc_offset_in_range (bfd *abfd, asection *input_section,
+				 arelent *reloc_entry, enum reloc_check check)
+{
+  if (check == check_inplace && !reloc_entry->howto->partial_inplace)
+    return true;
+  if (check == check_shuffle && !needs_shuffle (reloc_entry->howto->type))
+    return true;
+  return bfd_reloc_offset_in_range (reloc_entry->howto, abfd,
+				    input_section, reloc_entry->address);
+}
+
 bfd_reloc_status_type
 _bfd_mips_elf_gprel16_with_gp (bfd *abfd, asymbol *symbol,
 			       arelent *reloc_entry, asection *input_section,
@@ -2416,9 +2448,6 @@ _bfd_mips_elf_gprel16_with_gp (bfd *abfd, asymbol *symbol,
   relocation += symbol->section->output_section->vma;
   relocation += symbol->section->output_offset;
 
-  if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
-    return bfd_reloc_outofrange;
-
   /* Set val to the offset into the section or symbol.  */
   val = reloc_entry->addend;
 
@@ -2433,6 +2462,10 @@ _bfd_mips_elf_gprel16_with_gp (bfd *abfd, asymbol *symbol,
 
   if (reloc_entry->howto->partial_inplace)
     {
+      if (!bfd_reloc_offset_in_range (reloc_entry->howto, abfd, input_section,
+				      reloc_entry->address))
+	return bfd_reloc_outofrange;
+
       status = _bfd_relocate_contents (reloc_entry->howto, abfd, val,
 				       (bfd_byte *) data
 				       + reloc_entry->address);
@@ -2534,7 +2567,8 @@ _bfd_mips_elf_lo16_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
   bfd_vma vallo;
   bfd_byte *location = (bfd_byte *) data + reloc_entry->address;
 
-  if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
+  if (!bfd_reloc_offset_in_range (reloc_entry->howto, abfd, input_section,
+				  reloc_entry->address))
     return bfd_reloc_outofrange;
 
   _bfd_mips_elf_reloc_unshuffle (abfd, reloc_entry->howto->type, false,
@@ -2597,7 +2631,9 @@ _bfd_mips_elf_generic_reloc (bfd *abfd ATTRIBUTE_UNUSED, arelent *reloc_entry,
 
   relocatable = (output_bfd != NULL);
 
-  if (reloc_entry->address > bfd_get_section_limit (abfd, input_section))
+  if (!_bfd_mips_reloc_offset_in_range (abfd, input_section, reloc_entry,
+					(relocatable
+					 ? check_inplace : check_std)))
     return bfd_reloc_outofrange;
 
   /* Build up the field adjustment in VAL.  */
@@ -5819,6 +5855,8 @@ mips_elf_calculate_relocation (bfd *abfd, bfd *input_bfd,
     case R_MICROMIPS_CALL_LO16:
       if (resolved_to_zero
 	  && !bfd_link_relocatable (info)
+	  && bfd_reloc_offset_in_range (howto, input_bfd, input_section,
+					relocation->r_offset)
 	  && mips_elf_nullify_got_load (input_bfd, contents,
 					relocation, howto, true))
 	return bfd_reloc_continue;
@@ -8142,7 +8180,8 @@ mips_elf_rel_relocation_p (bfd *abfd, asection *sec,
    of the section that REL is against.  */
 
 static bfd_vma
-mips_elf_read_rel_addend (bfd *abfd, const Elf_Internal_Rela *rel,
+mips_elf_read_rel_addend (bfd *abfd, asection *sec,
+			  const Elf_Internal_Rela *rel,
 			  reloc_howto_type *howto, bfd_byte *contents)
 {
   bfd_byte *location;
@@ -8150,6 +8189,9 @@ mips_elf_read_rel_addend (bfd *abfd, const Elf_Internal_Rela *rel,
   bfd_vma addend;
   bfd_vma bytes;
 
+  if (!bfd_reloc_offset_in_range (howto, abfd, sec, rel->r_offset))
+    return 0;
+
   r_type = ELF_R_TYPE (abfd, rel->r_info);
   location = contents + rel->r_offset;
 
@@ -8176,6 +8218,7 @@ mips_elf_read_rel_addend (bfd *abfd, const Elf_Internal_Rela *rel,
 
 static bool
 mips_elf_add_lo16_rel_addend (bfd *abfd,
+			      asection *sec,
 			      const Elf_Internal_Rela *rel,
 			      const Elf_Internal_Rela *relend,
 			      bfd_byte *contents, bfd_vma *addend)
@@ -8218,7 +8261,8 @@ mips_elf_add_lo16_rel_addend (bfd *abfd,
 
   /* Obtain the addend kept there.  */
   lo16_howto = MIPS_ELF_RTYPE_TO_HOWTO (abfd, lo16_type, false);
-  l = mips_elf_read_rel_addend (abfd, lo16_relocation, lo16_howto, contents);
+  l = mips_elf_read_rel_addend (abfd, sec, lo16_relocation, lo16_howto,
+				contents);
 
   l <<= lo16_howto->rightshift;
   l = _bfd_mips_elf_sign_extend (l, 16);
@@ -8685,11 +8729,12 @@ _bfd_mips_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
 
 	      rel_reloc = mips_elf_rel_relocation_p (abfd, sec, relocs, rel);
 	      howto = MIPS_ELF_RTYPE_TO_HOWTO (abfd, r_type, !rel_reloc);
-
-	      if (!mips_elf_nullify_got_load (abfd, contents, rel, howto,
-					      false))
-		if (!mips_elf_define_absolute_zero (abfd, info, htab, r_type))
-		  return false;
+	      if (bfd_reloc_offset_in_range (howto, abfd, sec, rel->r_offset))
+		if (!mips_elf_nullify_got_load (abfd, contents, rel, howto,
+						false))
+		  if (!mips_elf_define_absolute_zero (abfd, info, htab,
+						      r_type))
+		    return false;
 	    }
 
 	  /* Fall through.  */
@@ -8903,10 +8948,10 @@ _bfd_mips_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
 		  if (!mips_elf_get_section_contents (abfd, sec, &contents))
 		    return false;
 		  howto = MIPS_ELF_RTYPE_TO_HOWTO (abfd, r_type, false);
-		  addend = mips_elf_read_rel_addend (abfd, rel,
+		  addend = mips_elf_read_rel_addend (abfd, sec, rel,
 						     howto, contents);
 		  if (got16_reloc_p (r_type))
-		    mips_elf_add_lo16_rel_addend (abfd, rel, rel_end,
+		    mips_elf_add_lo16_rel_addend (abfd, sec, rel, rel_end,
 						  contents, &addend);
 		  else
 		    addend <<= howto->rightshift;
@@ -10423,14 +10468,15 @@ _bfd_mips_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
 					 relocs, rel))
 	    {
 	      rela_relocation_p = false;
-	      addend = mips_elf_read_rel_addend (input_bfd, rel,
-						 howto, contents);
+	      addend = mips_elf_read_rel_addend (input_bfd, input_section,
+						 rel, howto, contents);
 	      if (hi16_reloc_p (r_type)
 		  || (got16_reloc_p (r_type)
 		      && mips_elf_local_relocation_p (input_bfd, rel,
 						      local_sections)))
 		{
-		  if (!mips_elf_add_lo16_rel_addend (input_bfd, rel, relend,
+		  if (!mips_elf_add_lo16_rel_addend (input_bfd, input_section,
+						     rel, relend,
 						     contents, &addend))
 		    {
 		      if (h)
diff --git a/bfd/elfxx-mips.h b/bfd/elfxx-mips.h
index af6d14c..6b22fda 100644
--- a/bfd/elfxx-mips.h
+++ b/bfd/elfxx-mips.h
@@ -22,6 +22,13 @@
 #include "elf/internal.h"
 #include "elf/mips.h"
 
+enum reloc_check
+{
+  check_std,
+  check_inplace,
+  check_shuffle
+};
+
 extern bool _bfd_mips_elf_mkobject
   (bfd *);
 extern bool _bfd_mips_elf_new_section_hook
@@ -129,6 +136,8 @@ extern void _bfd_mips_elf_reloc_unshuffle
   (bfd *, int, bool, bfd_byte *);
 extern void _bfd_mips_elf_reloc_shuffle
   (bfd *, int, bool, bfd_byte *);
+extern bool _bfd_mips_reloc_offset_in_range
+  (bfd *, asection *, arelent *, enum reloc_check);
 extern bfd_reloc_status_type _bfd_mips_elf_gprel16_with_gp
   (bfd *, asymbol *, arelent *, asection *, bool, void *, bfd_vma);
 extern bfd_reloc_status_type _bfd_mips_elf32_gprel16_reloc