PR 21274, ld segfaults linking PE DLL

Don't use fixed size buffers for symbol names.

	PR 21274
	PR 18466
	* emultempl/pe.em (pe_find_data_imports): Don't use fixed size
	symbol buffer.  Instead, xmalloc max size needed with space for
	prefix.  Wrap overlong lines.  Formatting.  Pass symbol buffer
	copy of name to pe_walk_relocs_of_symbol.
	(make_inport_fixup): Add "name" param, pass to pe_create_import_fixup.
	* emultempl/pe.em (pep_find_data_imports): As for pe_find_data_imports.
	(make_import_fixup): Add "name" param, pass to pep_create_import_fixup.
	Use bfd_get_signed_* and remove unnecessary casts.  Formatting.
	* pe-dll.c (pe_walk_relocs_of_symbol): Add "name" param.  Pass to
	callback.
	(make_import_fixup_mark): Add "name" param.  Make use of prefix
	space rather than xmalloc here.
	(pe_create_import_fixup): Likewise.
	* pe-dll.h (pe_walk_relocs_of_symbol): Update prototype.
	(pe_create_import_fixup): Likewise.
	* pep-dll.h (pep_walk_relocs_of_symbol): Likewise.
	(pep_create_import_fixup): Likewise.

ld/ChangeLog

@@ -1,3 +1,25 @@
+2017-04-11  Alan Modra  <amodra@gmail.com>
+
+	PR 21274
+	PR 18466
+	* emultempl/pe.em (pe_find_data_imports): Don't use fixed size
+	symbol buffer.  Instead, xmalloc max size needed with space for
+	prefix.  Wrap overlong lines.  Formatting.  Pass symbol buffer
+	copy of name to pe_walk_relocs_of_symbol.
+	(make_inport_fixup): Add "name" param, pass to pe_create_import_fixup.
+	* emultempl/pe.em (pep_find_data_imports): As for pe_find_data_imports.
+	(make_import_fixup): Add "name" param, pass to pep_create_import_fixup.
+	Use bfd_get_signed_* and remove unnecessary casts.  Formatting.
+	* pe-dll.c (pe_walk_relocs_of_symbol): Add "name" param.  Pass to
+	callback.
+	(make_import_fixup_mark): Add "name" param.  Make use of prefix
+	space rather than xmalloc here.
+	(pe_create_import_fixup): Likewise.
+	* pe-dll.h (pe_walk_relocs_of_symbol): Update prototype.
+	(pe_create_import_fixup): Likewise.
+	* pep-dll.h (pep_walk_relocs_of_symbol): Likewise.
+	(pep_create_import_fixup): Likewise.
+
 2017-04-10  Nick Clifton  <nickc@redhat.com>
 
 	* ld.texinfo (--strip-discarded): Document.

ld/emultempl/pe.em

@@ -1130,7 +1130,7 @@ pe_fixup_stdcalls (void)
 }
 
 static int
-make_import_fixup (arelent *rel, asection *s)
+make_import_fixup (arelent *rel, asection *s, char *name)
 {
   struct bfd_symbol *sym = *rel->sym_ptr_ptr;
   char addend[4];
@@ -1143,7 +1143,7 @@ make_import_fixup (arelent *rel, asection *s)
     einfo (_("%C: Cannot get section contents - auto-import exception\n"),
 	   s->owner, s, rel->address);
 
-  pe_create_import_fixup (rel, s, bfd_get_32 (s->owner, addend));
+  pe_create_import_fixup (rel, s, bfd_get_32 (s->owner, addend), name);
 
   return 1;
 }
@@ -1152,32 +1152,46 @@ static void
 pe_find_data_imports (void)
 {
   struct bfd_link_hash_entry *undef, *sym;
+  size_t namelen;
+  char *buf, *name;
 
   if (link_info.pei386_auto_import == 0)
     return;
 
-  for (undef = link_info.hash->undefs; undef; undef=undef->u.undef.next)
+  namelen = 0;
+  for (undef = link_info.hash->undefs; undef; undef = undef->u.undef.next)
     {
       if (undef->type == bfd_link_hash_undefined)
 	{
-	  /* C++ symbols are *long*.  */
+	  size_t len = strlen (undef->root.string);
-#define BUF_SIZE 4096
+	  if (namelen < len)
-	  char buf[BUF_SIZE];
+	    namelen = len;
+	}
+    }
+  if (namelen == 0)
+    return;
+
+  /* We are being a bit cunning here.  The buffer will have space for
+     prefixes at the beginning.  The prefix is modified here and in a
+     number of functions called from this function.  */
+#define PREFIX_LEN 32
+  buf = xmalloc (PREFIX_LEN + namelen + 1);
+  name = buf + PREFIX_LEN;
+
+  for (undef = link_info.hash->undefs; undef; undef = undef->u.undef.next)
+    {
+      if (undef->type == bfd_link_hash_undefined)
+	{
+	  char *impname;
 
 	  if (pe_dll_extra_pe_debug)
 	    printf ("%s:%s\n", __FUNCTION__, undef->root.string);
 
-	  if (strlen (undef->root.string) > (BUF_SIZE - 6))
+	  strcpy (name, undef->root.string);
-	    {
+	  impname = name - (sizeof "__imp_" - 1);
-	      /* PR linker/18466.  */
+	  memcpy (impname, "__imp_", sizeof "__imp_" - 1);
-	      einfo (_("%P: internal error: symbol too long: %s\n"),
-		     undef->root.string);
-	      return;
-	    }
 
-	  sprintf (buf, "__imp_%s", undef->root.string);
+	  sym = bfd_link_hash_lookup (link_info.hash, impname, 0, 0, 1);
-
-	  sym = bfd_link_hash_lookup (link_info.hash, buf, 0, 0, 1);
 
 	  if (sym && sym->type == bfd_link_hash_defined)
 	    {
@@ -1189,15 +1203,18 @@ pe_find_data_imports (void)
 		{
 		  static bfd_boolean warned = FALSE;
 
-		  info_msg (_("Info: resolving %s by linking to %s (auto-import)\n"),
+		  info_msg (_("Info: resolving %s by linking to %s "
-			    undef->root.string, buf);
+			      "(auto-import)\n"), name, impname);
 
 		  /* PR linker/4844.  */
 		  if (! warned)
 		    {
 		      warned = TRUE;
-		      einfo (_("%P: warning: auto-importing has been activated without --enable-auto-import specified on the command line.\n\
+		      einfo (_("%P: warning: auto-importing has been activated "
-This should work unless it involves constant data structures referencing symbols from auto-imported DLLs.\n"));
+			       "without --enable-auto-import specified on the "
+			       "command line.\nThis should work unless it "
+			       "involves constant data structures referencing "
+			       "symbols from auto-imported DLLs.\n"));
 		    }
 		}
 
@@ -1212,8 +1229,7 @@ This should work unless it involves constant data structures referencing symbols
 
 	      for (i = 0; i < nsyms; i++)
 		{
-		  if (! CONST_STRNEQ (symbols[i]->name,
+		  if (! CONST_STRNEQ (symbols[i]->name, U ("_head_")))
-				      U ("_head_")))
 		    continue;
 
 		  if (pe_dll_extra_pe_debug)
@@ -1224,8 +1240,7 @@ This should work unless it involves constant data structures referencing symbols
 		  break;
 		}
 
-	      pe_walk_relocs_of_symbol (&link_info, undef->root.string,
+	      pe_walk_relocs_of_symbol (&link_info, name, make_import_fixup);
-					make_import_fixup);
 
 	      /* Let's differentiate it somehow from defined.  */
 	      undef->type = bfd_link_hash_defweak;
@@ -1238,6 +1253,7 @@ This should work unless it involves constant data structures referencing symbols
 	    }
 	}
     }
+  free (buf);
 }
 
 static bfd_boolean

ld/emultempl/pep.em

@@ -1075,7 +1075,7 @@ pep_fixup_stdcalls (void)
 }
 
 static int
-make_import_fixup (arelent *rel, asection *s)
+make_import_fixup (arelent *rel, asection *s, char *name)
 {
   struct bfd_symbol *sym = *rel->sym_ptr_ptr;
   char addend[8];
@@ -1089,32 +1089,32 @@ make_import_fixup (arelent *rel, asection *s)
   memset (addend, 0, sizeof (addend));
   switch ((rel->howto->bitsize))
     {
-      case 8:
+    case 8:
-        suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 1);
+      suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 1);
-        if (suc && rel->howto->pc_relative)
+      if (suc && rel->howto->pc_relative)
-          _addend = (bfd_vma) ((bfd_signed_vma) ((char) bfd_get_8 (s->owner, addend)));
+	_addend = bfd_get_signed_8 (s->owner, addend);
-        else if (suc)
+      else if (suc)
-          _addend = ((bfd_vma) bfd_get_8 (s->owner, addend)) & 0xff;
+	_addend = bfd_get_8 (s->owner, addend);
-        break;
+      break;
-      case 16:
+    case 16:
-        suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 2);
+      suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 2);
-        if (suc && rel->howto->pc_relative)
+      if (suc && rel->howto->pc_relative)
-          _addend = (bfd_vma) ((bfd_signed_vma) ((short) bfd_get_16 (s->owner, addend)));
+	_addend = bfd_get_signed_16 (s->owner, addend);
-        else if (suc)
+      else if (suc)
-          _addend = ((bfd_vma) bfd_get_16 (s->owner, addend)) & 0xffff;
+	_addend = bfd_get_16 (s->owner, addend);
-        break;
+      break;
-      case 32:
+    case 32:
-        suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 4);
+      suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 4);
-        if (suc && rel->howto->pc_relative)
+      if (suc && rel->howto->pc_relative)
-          _addend = (bfd_vma) ((bfd_signed_vma) ((int) bfd_get_32 (s->owner, addend)));
+	_addend = bfd_get_signed_32 (s->owner, addend);
-        else if (suc)
+      else if (suc)
-          _addend = ((bfd_vma) bfd_get_32 (s->owner, addend)) & 0xffffffff;
+	_addend = bfd_get_32 (s->owner, addend);
-        break;
+      break;
-      case 64:
+    case 64:
-        suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 8);
+      suc = bfd_get_section_contents (s->owner, s, addend, rel->address, 8);
-        if (suc)
+      if (suc)
-          _addend = ((bfd_vma) bfd_get_64 (s->owner, addend));
+	_addend = bfd_get_64 (s->owner, addend);
-        break;
+      break;
     }
   if (! suc)
     einfo (_("%C: Cannot get section contents - auto-import exception\n"),
@@ -1122,11 +1122,13 @@ make_import_fixup (arelent *rel, asection *s)
 
   if (pep_dll_extra_pe_debug)
     {
-      printf ("import of 0x%lx(0x%lx) sec_addr=0x%lx", (long) _addend, (long) rel->addend, (long) rel->address);
+      printf ("import of 0x%lx(0x%lx) sec_addr=0x%lx",
-      if (rel->howto->pc_relative) printf (" pcrel");
+	      (long) _addend, (long) rel->addend, (long) rel->address);
-      printf (" %d bit rel.\n",(int) rel->howto->bitsize);
+      if (rel->howto->pc_relative)
-  }
+	printf (" pcrel");
-  pep_create_import_fixup (rel, s, _addend);
+      printf (" %d bit rel.\n", (int) rel->howto->bitsize);
+    }
+  pep_create_import_fixup (rel, s, _addend, name);
 
   return 1;
 }
@@ -1135,32 +1137,46 @@ static void
 pep_find_data_imports (void)
 {
   struct bfd_link_hash_entry *undef, *sym;
+  size_t namelen;
+  char *buf, *name;
 
   if (link_info.pei386_auto_import == 0)
     return;
 
-  for (undef = link_info.hash->undefs; undef; undef=undef->u.undef.next)
+  namelen = 0;
+  for (undef = link_info.hash->undefs; undef; undef = undef->u.undef.next)
     {
       if (undef->type == bfd_link_hash_undefined)
 	{
-	  /* C++ symbols are *long*.  */
+	  size_t len = strlen (undef->root.string);
-#define BUF_SIZE 4096
+	  if (namelen < len)
-	  char buf[BUF_SIZE];
+	    namelen = len;
+	}
+    }
+  if (namelen == 0)
+    return;
+
+  /* We are being a bit cunning here.  The buffer will have space for
+     prefixes at the beginning.  The prefix is modified here and in a
+     number of functions called from this function.  */
+#define PREFIX_LEN 32
+  buf = xmalloc (PREFIX_LEN + namelen + 1);
+  name = buf + PREFIX_LEN;
+
+  for (undef = link_info.hash->undefs; undef; undef = undef->u.undef.next)
+    {
+      if (undef->type == bfd_link_hash_undefined)
+	{
+	  char *impname;
 
 	  if (pep_dll_extra_pe_debug)
 	    printf ("%s:%s\n", __FUNCTION__, undef->root.string);
 
-	  if (strlen (undef->root.string) > (BUF_SIZE - 6))
+	  strcpy (name, undef->root.string);
-	    {
+	  impname = name - (sizeof "__imp_" - 1);
-	      /* PR linker/18466.  */
+	  memcpy (impname, "__imp_", sizeof "__imp_" - 1);
-	      einfo (_("%P: internal error: symbol too long: %s\n"),
-		     undef->root.string);
-	      return;
-	    }
 
-	  sprintf (buf, "__imp_%s", undef->root.string);
+	  sym = bfd_link_hash_lookup (link_info.hash, impname, 0, 0, 1);
-
-	  sym = bfd_link_hash_lookup (link_info.hash, buf, 0, 0, 1);
 
 	  if (sym && sym->type == bfd_link_hash_defined)
 	    {
@@ -1185,13 +1201,12 @@ pep_find_data_imports (void)
 		  if (pep_dll_extra_pe_debug)
 		    printf ("->%s\n", symbols[i]->name);
 
-		  pep_data_import_dll = (char*) (symbols[i]->name +
+		  pep_data_import_dll = (char *) (symbols[i]->name
-						 U_SIZE ("_head_") - 1);
+						  + U_SIZE ("_head_") - 1);
 		  break;
 		}
 
-	      pep_walk_relocs_of_symbol (&link_info, undef->root.string,
+	      pep_walk_relocs_of_symbol (&link_info, name, make_import_fixup);
-					 make_import_fixup);
 
 	      /* Let's differentiate it somehow from defined.  */
 	      undef->type = bfd_link_hash_defweak;
@@ -1204,6 +1219,7 @@ pep_find_data_imports (void)
 	    }
 	}
     }
+  free (buf);
 }
 
 static bfd_boolean

ld/pe-dll.c

@@ -1275,8 +1275,8 @@ static struct bfd_section *current_sec;
 
 void
 pe_walk_relocs_of_symbol (struct bfd_link_info *info,
-			  const char *name,
+			  char *name,
-			  int (*cb) (arelent *, asection *))
+			  int (*cb) (arelent *, asection *, char *))
 {
   bfd *b;
   asection *s;
@@ -1315,7 +1315,7 @@ pe_walk_relocs_of_symbol (struct bfd_link_info *info,
 	      struct bfd_symbol *sym = *relocs[i]->sym_ptr_ptr;
 
 	      if (!strcmp (name, sym->name))
-		cb (relocs[i], s);
+		cb (relocs[i], s, name);
 	    }
 
 	  free (relocs);
@@ -2396,37 +2396,21 @@ make_singleton_name_thunk (const char *import, bfd *parent)
 }
 
 static char *
-make_import_fixup_mark (arelent *rel)
+make_import_fixup_mark (arelent *rel, char *name)
 {
   /* We convert reloc to symbol, for later reference.  */
-  static int counter;
+  static unsigned int counter;
-  static char *fixup_name = NULL;
-  static size_t buffer_len = 0;
-
   struct bfd_symbol *sym = *rel->sym_ptr_ptr;
-
   bfd *abfd = bfd_asymbol_bfd (sym);
   struct bfd_link_hash_entry *bh;
+  char *fixup_name, buf[26];
+  size_t prefix_len;
 
-  if (!fixup_name)
+  /* "name" buffer has space before the symbol name for prefixes.  */
-    {
+  sprintf (buf, "__fu%d_", counter++);
-      fixup_name = xmalloc (384);
+  prefix_len = strlen (buf);
-      buffer_len = 384;
+  fixup_name = name - prefix_len;
-    }
+  memcpy (fixup_name, buf, prefix_len);
-
-  if (strlen (sym->name) + 25 > buffer_len)
-  /* Assume 25 chars for "__fu" + counter + "_".  If counter is
-     bigger than 20 digits long, we've got worse problems than
-     overflowing this buffer...  */
-    {
-      free (fixup_name);
-      /* New buffer size is length of symbol, plus 25, but
-	 then rounded up to the nearest multiple of 128.  */
-      buffer_len = ((strlen (sym->name) + 25) + 127) & ~127;
-      fixup_name = xmalloc (buffer_len);
-    }
-
-  sprintf (fixup_name, "__fu%d_%s", counter++, sym->name);
 
   bh = NULL;
   bfd_coff_link_add_one_symbol (&link_info, abfd, fixup_name, BSF_GLOBAL,
@@ -2626,23 +2610,25 @@ pe_create_runtime_relocator_reference (bfd *parent)
 }
 
 void
-pe_create_import_fixup (arelent *rel, asection *s, bfd_vma addend)
+pe_create_import_fixup (arelent *rel, asection *s, bfd_vma addend, char *name)
 {
-  char buf[300];
   struct bfd_symbol *sym = *rel->sym_ptr_ptr;
   struct bfd_link_hash_entry *name_thunk_sym;
   struct bfd_link_hash_entry *name_imp_sym;
-  const char *name = sym->name;
+  char *fixup_name, *impname;
-  char *fixup_name = make_import_fixup_mark (rel);
   bfd *b;
   int need_import_table = 1;
 
-  sprintf (buf, "__imp_%s", name);
+  /* name buffer is allocated with space at beginning for prefixes.  */
-  name_imp_sym = bfd_link_hash_lookup (link_info.hash, buf, 0, 0, 1);
+  impname = name - (sizeof "__imp_" - 1);
+  memcpy (impname, "__imp_", sizeof "__imp_" - 1);
+  name_imp_sym = bfd_link_hash_lookup (link_info.hash, impname, 0, 0, 1);
 
-  sprintf (buf, "__nm_thnk_%s", name);
+  impname = name - (sizeof "__nm_thnk_" - 1);
+  memcpy (impname, "__nm_thnk_", sizeof "__nm_thnk_" - 1);
+  name_thunk_sym = bfd_link_hash_lookup (link_info.hash, impname, 0, 0, 1);
 
-  name_thunk_sym = bfd_link_hash_lookup (link_info.hash, buf, 0, 0, 1);
+  fixup_name = make_import_fixup_mark (rel, name);
 
   /* For version 2 pseudo relocation we don't need to add an import
      if the import symbol is already present.  */

ld/pe-dll.h

@@ -62,9 +62,9 @@ extern void pe_dll_fill_sections
 extern void pe_exe_fill_sections
   (bfd *, struct bfd_link_info *);
 extern void pe_walk_relocs_of_symbol
-  (struct bfd_link_info *, const char *, int (*) (arelent *, asection *));
+  (struct bfd_link_info *, char *, int (*) (arelent *, asection *, char *));
 extern void pe_create_import_fixup
-  (arelent * rel, asection *, bfd_vma);
+  (arelent * rel, asection *, bfd_vma, char *);
 extern bfd_boolean pe_bfd_is_dll
   (bfd *);
 extern void pe_output_file_set_long_section_names

ld/pep-dll.h

@@ -53,8 +53,9 @@ extern void pep_exe_build_sections  (bfd *, struct bfd_link_info *);
 extern void pep_dll_fill_sections  (bfd *, struct bfd_link_info *);
 extern void pep_exe_fill_sections  (bfd *, struct bfd_link_info *);
 extern void pep_walk_relocs_of_symbol
-  (struct bfd_link_info *, const char *, int (*) (arelent *, asection *));
+  (struct bfd_link_info *, char *, int (*) (arelent *, asection *, char *));
-extern void pep_create_import_fixup  (arelent * rel, asection *, bfd_vma);
+extern void pep_create_import_fixup  (arelent * rel, asection *, bfd_vma,
+				      char *);
 extern bfd_boolean pep_bfd_is_dll  (bfd *);
 extern void pep_output_file_set_long_section_names (bfd *);