asan: NULL dereference in bfd_elf_set_group_contents

[Alan Modra]

	* elf-bfd.h (struct output_elf_obj_tdata): Make num_section_syms
	unsigned.
	* elf.c (bfd_elf_set_group_contents): Bounds check sec->index
	and check that entry in elf_section_syms for sec is non-NULL.
	(_bfd_elf_symbol_from_bfd_symbol): Adjust.

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 91bb1b2b8bd..68e830c6f05 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1914,7 +1914,7 @@ struct output_elf_obj_tdata
   /* Linker information.  */
   struct bfd_link_info *link_info;
 
-  int num_section_syms;
+  unsigned int num_section_syms;
   unsigned int shstrtab_section, strtab_section;
 
   /* Segment flags for the PT_GNU_STACK segment.  */
diff --git a/bfd/elf.c b/bfd/elf.c
index e6c6a8a6c05..92c06f2e44f 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -3501,7 +3501,8 @@ bfd_elf_set_group_contents (bfd *abfd, asection *sec, void *failedptrarg)
 	  /* If called from the assembler, swap_out_syms will have set up
 	     elf_section_syms.
 	     PR 25699: A corrupt input file could contain bogus group info.  */
-	  if (elf_section_syms (abfd) == NULL)
+	  if (sec->index >= elf_num_section_syms (abfd)
+	      || elf_section_syms (abfd)[sec->index] == NULL)
 	    {
 	      *failedptr = true;
 	      return;
@@ -6764,15 +6765,14 @@ _bfd_elf_symbol_from_bfd_symbol (bfd *abfd, asymbol **asym_ptr_ptr)
       && asym_ptr->section)
     {
       asection *sec;
-      int indx;
 
       sec = asym_ptr->section;
       if (sec->owner != abfd && sec->output_section != NULL)
 	sec = sec->output_section;
       if (sec->owner == abfd
-	  && (indx = sec->index) < elf_num_section_syms (abfd)
-	  && elf_section_syms (abfd)[indx] != NULL)
-	asym_ptr->udata.i = elf_section_syms (abfd)[indx]->udata.i;
+	  && sec->index < elf_num_section_syms (abfd)
+	  && elf_section_syms (abfd)[sec->index] != NULL)
+	asym_ptr->udata.i = elf_section_syms (abfd)[sec->index]->udata.i;
     }
 
   idx = asym_ptr->udata.i;

-- 
Alan Modra
Australia Development Lab, IBM