PR29846, segmentation fault in objdump.c compare_symbols

[Alan Modra <amodra@gmail.com>]

Fixes a fuzzed object file problem where plt relocs were manipulated
in such a way that two synthetic symbols were generated at the same
plt location.  Won't occur in real object files.

	PR 29846
	PR 20337
	* objdump.c (compare_symbols): Test symbol flags to exclude
	section and synthetic symbols before attempting to check flavour.

diff --git a/binutils/objdump.c b/binutils/objdump.c
index e8481b2d928..d95c8b68bf0 100644
--- a/binutils/objdump.c
+++ b/binutils/objdump.c
@@ -1222,20 +1222,17 @@ compare_symbols (const void *ap, const void *bp)
 	return 1;
     }
 
-  if (bfd_get_flavour (bfd_asymbol_bfd (a)) == bfd_target_elf_flavour
+  /* Sort larger size ELF symbols before smaller.  See PR20337.  */
+  bfd_vma asz = 0;
+  if ((a->flags & (BSF_SECTION_SYM | BSF_SYNTHETIC)) == 0
+      && bfd_get_flavour (bfd_asymbol_bfd (a)) == bfd_target_elf_flavour)
+    asz = ((elf_symbol_type *) a)->internal_elf_sym.st_size;
+  bfd_vma bsz = 0;
+  if ((b->flags & (BSF_SECTION_SYM | BSF_SYNTHETIC)) == 0
       && bfd_get_flavour (bfd_asymbol_bfd (b)) == bfd_target_elf_flavour)
-    {
-      bfd_vma asz, bsz;
-
-      asz = 0;
-      if ((a->flags & (BSF_SECTION_SYM | BSF_SYNTHETIC)) == 0)
-	asz = ((elf_symbol_type *) a)->internal_elf_sym.st_size;
-      bsz = 0;
-      if ((b->flags & (BSF_SECTION_SYM | BSF_SYNTHETIC)) == 0)
-	bsz = ((elf_symbol_type *) b)->internal_elf_sym.st_size;
-      if (asz != bsz)
-	return asz > bsz ? -1 : 1;
-    }
+    bsz = ((elf_symbol_type *) b)->internal_elf_sym.st_size;
+  if (asz != bsz)
+    return asz > bsz ? -1 : 1;
 
   /* Symbols that start with '.' might be section names, so sort them
      after symbols that don't start with '.'.  */

-- 
Alan Modra
Australia Development Lab, IBM