PR24355, segmentation fault in function called from ppc_finish_symbols

This one looks to be a bug going back to 2009, git commit e054468f6c
"STT_GNU_IFUNC support for PowerPC".  That bug was carried over with
git commit 49c09209d0 "Rearrange PLT reloc output on powerpc".

If the refcount for an ifunc local sym plt entry was zero,
ppc_elf_size_dynamic_sections would correctly set plt.offset to -1 but
leave glink_offset uninitialized.  That leads to occasional segfaults
(which can be made solid with MALLOC_PERTURB_=1 when using glibc).
So, guard the write_glink_stub call with plt.offset != -1.  Also,
remove the totally ineffective attempt at writing multiple-use glink
stubs only once.

	PR 24355
	* elf32-ppc.c (ppc_finish_symbols): Don't call write_glink_stub
	for local iplt syms with ent->plt.offset == -1.  Remove ineffective
	attempt at writing glink stubs only once.

(cherry picked from commit 8cd1fe1bf525b59f4d07e5790d11d49eee7e8494)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 4582b8c5086e688ead3d408bac6ba8fb7895ec40..eb32e2dd679347e5c623e4fb76c1a378dc0608f9 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2019-03-18  Alan Modra  <amodra@gmail.com>
+
+       PR 24355
+       * elf32-ppc.c (ppc_finish_symbols): Don't call write_glink_stub
+       for local iplt syms with ent->plt.offset == -1.  Remove ineffective
+       attempt at writing glink stubs only once.
+
 2019-02-18  Nick Clifton  <nickc@redhat.com>
 
        Import from the mainline:

diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 5e9251bdb9faad12b85d26fb03c41a50e243cfb9..f4a329a13270bd986f9e08d3c499bf7529ccefb3 100644 (file)
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -10828,6 +10828,7 @@ ppc_finish_symbols (struct bfd_link_info *info)
                bfd_byte *loc;
                bfd_vma val;
                Elf_Internal_Rela rela;
+               unsigned char *p;
 
                if (!get_sym_h (NULL, &sym, &sym_sec, NULL, &local_syms,
                                lplt - local_plt, ibfd))
@@ -10872,14 +10873,9 @@ ppc_finish_symbols (struct bfd_link_info *info)
                loc = relplt->contents + (relplt->reloc_count++
                                          * sizeof (Elf32_External_Rela));
                bfd_elf32_swap_reloca_out (info->output_bfd, &rela, loc);
-             }
-           if ((ent->glink_offset & 1) == 0)
-             {
-               unsigned char *p = ((unsigned char *) htab->glink->contents
-                                   + ent->glink_offset);
 
+               p = (unsigned char *) htab->glink->contents + ent->glink_offset;
                write_glink_stub (NULL, ent, htab->elf.iplt, p, info);
-               ent->glink_offset |= 1;
              }
          }