[PATCH 1/2] LoongArch: Avoid heap-buffer-overflow in loongarch_elf_relocate_section

[Xi Ruoyao]

On Wed, 2022-09-14 at 18:15 +0800, Xi Ruoyao via Binutils wrote:

> > Shouldn't write to got table when using hidden ifunc.
> 
> Perhaps it's true, using RELA to resolve a GOT entry should not depend
> on any "initial" value of the entry...


How about this?  We don't need to write into the GOT if R_LARCH_RELATIVE
or R_LARCH_IRELATIVE will be used:

diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index a9bb66a1e04..1e8ecb2b8e2 100644
--- a/bfd/elfnn-loongarch.c
+++ b/bfd/elfnn-loongarch.c
@@ -3129,6 +3129,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
 	      BFD_ASSERT (rel->r_addend == 0);
 
 	      bfd_vma got_off = 0;
+	      bool fill_got_entry = true;
 	      if (h != NULL)
 		{
 		  /* GOT ref or ifunc.  */
@@ -3141,6 +3142,10 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
 		  if (h->got.offset == MINUS_ONE && h->type == STT_GNU_IFUNC)
 		    {
 		      bfd_vma idx;
+
+		      /* An IFUNC is always resolved at runtime.  */
+		      fill_got_entry = false;
+
 		      if (htab->elf.splt != NULL)
 			{
 			  idx = (h->plt.offset - PLT_HEADER_SIZE)
@@ -3177,6 +3182,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
 			  rela.r_addend = relocation;
 			  loongarch_elf_append_rela (output_bfd,
 						     htab->elf.srelgot, &rela);
+			  fill_got_entry = false;
 			}
 		      h->got.offset |= 1;
 		    }
@@ -3197,12 +3203,14 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
 			  rela.r_addend = relocation;
 			  loongarch_elf_append_rela (output_bfd,
 						     htab->elf.srelgot, &rela);
+			  fill_got_entry = false;
 			}
 		      local_got_offsets[r_symndx] |= 1;
 		    }
 		}
 
-	      bfd_put_NN (output_bfd, relocation, got->contents + got_off);
+	      if (fill_got_entry)
+		bfd_put_NN (output_bfd, relocation, got->contents + got_off);
 
 	      relocation = got_off + sec_addr (got);
 	    }

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University