Fix seg-fault in strip when copying a file containing corrupt secondary relocs.

PR 25673
	* elf.c (_bfd_elf_write_secondary_reloc_section): Fix illegal
	memory access when processing a corrupt secondary reloc section.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2020-03-18  Nick Clifton  <nickc@redhat.com>
+
+	PR 25673
+	* elf.c (_bfd_elf_write_secondary_reloc_section): Fix illegal
+	memory access when processing a corrupt secondary reloc section.
+
 2020-03-18  Christophe Lyon  <christophe.lyon@linaro.org>
 
 	* elf32-arm.c (arm_build_one_stub): Emit a fatal error message

bfd/elf.c

@@ -12637,6 +12637,10 @@ _bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)
   bfd_vma addr_offset;
   asection * relsec;
   bfd_vma (*r_info) (bfd_vma, bfd_vma);
+  bfd_boolean result = TRUE;
+
+  if (sec == NULL)
+    return FALSE;
 
 #if BFD_DEFAULT_TARGET_SIZE > 32
   if (bfd_arch_bits_per_address (abfd) != 32)
@@ -12645,9 +12649,6 @@ _bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)
 #endif
     r_info = elf32_r_info;
 
-  if (sec == NULL)
-    return FALSE;
-
   /* The address of an ELF reloc is section relative for an object
      file, and absolute for an executable file or shared library.
      The address of a BFD reloc is always section relative.  */
@@ -12672,10 +12673,28 @@ _bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)
 	  arelent *    src_irel;
 	  bfd_byte *   dst_rela;
 
-	  BFD_ASSERT (hdr->contents == NULL);
+	  if (hdr->contents != NULL)
+	    {
+	      _bfd_error_handler
+		/* xgettext:c-format */
+		(_("%pB(%pA): error: secondary reloc section processed twice"),
+		 abfd, relsec);
+	      bfd_set_error (bfd_error_bad_value);
+	      result = FALSE;
+	      continue;
+	    }
 
 	  reloc_count = hdr->sh_size / hdr->sh_entsize;
-	  BFD_ASSERT (reloc_count > 0);
+	  if (reloc_count <= 0)
+	    {
+	      _bfd_error_handler
+		/* xgettext:c-format */
+		(_("%pB(%pA): error: secondary reloc section is empty!"),
+		 abfd, relsec);
+	      bfd_set_error (bfd_error_bad_value);
+	      result = FALSE;
+	      continue;
+	    }
 
 	  hdr->contents = bfd_alloc (abfd, hdr->sh_size);
 	  if (hdr->contents == NULL)
@@ -12689,7 +12708,16 @@ _bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)
 	  last_sym_idx = 0;
 	  dst_rela = hdr->contents;
 	  src_irel = (arelent *) esd->sec_info;
-	  BFD_ASSERT (src_irel != NULL);
+	  if (src_irel == NULL)
+	    {
+	      _bfd_error_handler
+		/* xgettext:c-format */
+		(_("%pB(%pA): error: internal relocs missing for secondary reloc section"),
+		 abfd, relsec);
+	      bfd_set_error (bfd_error_bad_value);
+	      result = FALSE;
+	      continue;
+	    }
 
 	  for (idx = 0; idx < reloc_count; idx++, dst_rela += hdr->sh_entsize)
 	    {
@@ -12699,55 +12727,78 @@ _bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)
 	      int n;
 
 	      ptr = src_irel + idx;
-	      sym = *ptr->sym_ptr_ptr;
+	      if (ptr == NULL)
+		{
+		  _bfd_error_handler
+		    /* xgettext:c-format */
+		    (_("%pB(%pA): error: reloc table entry %u is empty"),
+		     abfd, relsec, idx);
+		  bfd_set_error (bfd_error_bad_value);
+		  result = FALSE;
+		  break;
+		}
 
-	      if (sym == last_sym)
-		n = last_sym_idx;
+	      if (ptr->sym_ptr_ptr == NULL)
+		{
+		  /* FIXME: Is this an error ? */
+		  n = 0;
+		}
 	      else
 		{
-		  last_sym = sym;
-		  n = _bfd_elf_symbol_from_bfd_symbol (abfd, & sym);
-		  if (n < 0)
+		  sym = *ptr->sym_ptr_ptr;
+
+		  if (sym == last_sym)
+		    n = last_sym_idx;
+		  else
 		    {
-#if DEBUG_SECONDARY_RELOCS
-		      fprintf (stderr, "failed to find symbol %s whilst rewriting relocs\n",
-			       sym->name);
-#endif
-		      /* FIXME: Signal failure somehow.  */
-		      n = 0;
+		      n = _bfd_elf_symbol_from_bfd_symbol (abfd, & sym);
+		      if (n < 0)
+			{
+			  _bfd_error_handler
+			    /* xgettext:c-format */
+			    (_("%pB(%pA): error: secondary reloc %u references a missing symbol"),
+			     abfd, relsec, idx);
+			  bfd_set_error (bfd_error_bad_value);
+			  result = FALSE;
+			  n = 0;
+			}
+
+		      last_sym = sym;
+		      last_sym_idx = n;
 		    }
-		  last_sym_idx = n;
-		}
 
-	      if ((*ptr->sym_ptr_ptr)->the_bfd != NULL
-		  && (*ptr->sym_ptr_ptr)->the_bfd->xvec != abfd->xvec
-		  && ! _bfd_elf_validate_reloc (abfd, ptr))
-		{
-#if DEBUG_SECONDARY_RELOCS
-		  fprintf (stderr, "symbol %s is not in the output bfd\n",
-			   sym->name);
-#endif
-		  /* FIXME: Signal failure somehow.  */
-		  n = 0;
+		  if (sym->the_bfd != NULL
+		      && sym->the_bfd->xvec != abfd->xvec
+		      && ! _bfd_elf_validate_reloc (abfd, ptr))
+		    {
+		      _bfd_error_handler
+			/* xgettext:c-format */
+			(_("%pB(%pA): error: secondary reloc %u references a deleted symbol"),
+			 abfd, relsec, idx);
+		      bfd_set_error (bfd_error_bad_value);
+		      result = FALSE;
+		      n = 0;
+		    }
 		}
 
+	      src_rela.r_offset = ptr->address + addr_offset;
 	      if (ptr->howto == NULL)
 		{
-#if DEBUG_SECONDARY_RELOCS
-		  fprintf (stderr, "reloc for symbol %s does not have a howto associated with it\n",
-			   sym->name);
-#endif
-		  /* FIXME: Signal failure somehow.  */
-		  n = 0;
+		  _bfd_error_handler
+		    /* xgettext:c-format */
+		    (_("%pB(%pA): error: secondary reloc %u is of an unknown type"),
+		     abfd, relsec, idx);
+		  bfd_set_error (bfd_error_bad_value);
+		  result = FALSE;
+		  src_rela.r_info = r_info (0, 0);
 		}
-
-	      src_rela.r_offset = ptr->address + addr_offset;
-	      src_rela.r_info = r_info (n, ptr->howto->type);
+	      else
+		src_rela.r_info = r_info (n, ptr->howto->type);
 	      src_rela.r_addend = ptr->addend;
 	      ebd->s->swap_reloca_out (abfd, &src_rela, dst_rela);
 	    }
 	}
     }
 
-  return TRUE;
+  return result;
 }