PR22552, readelf heap buffer overflow in load_debug_section

[Alan Modra]

	PR 22552
	* readelf.c (process_file_header): Don't assume XINDEX case
	value for e_shstrndx is within bounds.
	(load_debug_section): Sanity test e_shstrndx before attempting
	to read .shstrtab.  Wrap long lines.

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index 5139c6b..efc88e0 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,11 @@
+2017-12-06  Alan Modra  <amodra@gmail.com>
+
+	PR 22552
+	* readelf.c (process_file_header): Don't assume XINDEX case
+	value for e_shstrndx is within bounds.
+	(load_debug_section): Sanity test e_shstrndx before attempting
+	to read .shstrtab.  Wrap long lines.
+
 2017-12-01  Oleksandr Pikozh  <o.pikozh@gmail.com>
 
 	* doc/binutils.texi: Add --strip-unneeded to objcopy synopsis.
diff --git a/binutils/readelf.c b/binutils/readelf.c
index e0230c7..8a31ebb 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -4761,7 +4761,7 @@ process_file_header (Filedata * filedata)
 	header->e_shnum = filedata->section_headers[0].sh_size;
       if (header->e_shstrndx == (SHN_XINDEX & 0xffff))
 	header->e_shstrndx = filedata->section_headers[0].sh_link;
-      else if (header->e_shstrndx >= header->e_shnum)
+      if (header->e_shstrndx >= header->e_shnum)
 	header->e_shstrndx = SHN_UNDEF;
       free (filedata->section_headers);
       filedata->section_headers = NULL;
@@ -13578,7 +13578,9 @@ load_debug_section (enum dwarf_section_display_enum debug, void * data)
   if (filedata->section_headers == NULL)
     return FALSE;
 
-  if (filedata->string_table == NULL)
+  if (filedata->string_table == NULL
+      && filedata->file_header.e_shstrndx != SHN_UNDEF
+      && filedata->file_header.e_shstrndx < filedata->file_header.e_shnum)
     {
       Elf_Internal_Shdr * strs;
 
@@ -13587,11 +13589,12 @@ load_debug_section (enum dwarf_section_display_enum debug, void * data)
 
       if (strs != NULL && strs->sh_size != 0)
 	{
-	  filedata->string_table = (char *) get_data (NULL, filedata, strs->sh_offset,
-						      1, strs->sh_size,
-						      _("string table"));
+	  filedata->string_table
+	    = (char *) get_data (NULL, filedata, strs->sh_offset,
+				 1, strs->sh_size, _("string table"));
 
-	  filedata->string_table_length = filedata->string_table != NULL ? strs->sh_size : 0;
+	  filedata->string_table_length
+	    = filedata->string_table != NULL ? strs->sh_size : 0;
 	}
     }
 

-- 
Alan Modra
Australia Development Lab, IBM