Future safety in checking ELF header.

If we should use further fields in the e_ident array in the ELF header
of files we want zero to mean the default.  Enforce zero for now so
that non-optional features indicated by nonzero values are not go
unnoticed when using an old dynamic linker.

diff --git a/ChangeLog b/ChangeLog
index 92b6a91..9ff497d 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2010-03-18  Ulrich Drepper  <drepper@redhat.com>
+
+       * elf/dl-load.c (open_verify): Extend expected to the full size of the
+       e_ident array.  When loading, check that the fields in e_ident we don't
+       know are zero to allow future extensions.
+
 2010-03-18  H.J. Lu  <hongjiu.lu@intel.com>
 
        * sysdeps/i386/i686/multiarch/memcmp-ssse3.S: Update %xmm3

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 756816f..d8f9131 100644 (file)
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1573,7 +1573,7 @@ open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
 #elif defined MORE_ELF_HEADER_DATA
   MORE_ELF_HEADER_DATA;
 #endif
-  static const unsigned char expected[EI_PAD] =
+  static const unsigned char expected[EI_NIDENT] =
   {
     [EI_MAG0] = ELFMAG0,
     [EI_MAG1] = ELFMAG1,
@@ -1657,7 +1657,10 @@ open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
       if (__builtin_expect (! VALID_ELF_HEADER (ehdr->e_ident, expected,
                                                EI_ABIVERSION)
                            || !VALID_ELF_ABIVERSION (ehdr->e_ident[EI_OSABI],
-                                                     ehdr->e_ident[EI_ABIVERSION]),
+                                                     ehdr->e_ident[EI_ABIVERSION])
+                           || memcmp (&ehdr->e_ident[EI_PAD],
+                                      &expected[EI_PAD],
+                                      EI_NIDENT - EI_PAD) != 0,
                            0))
        {
          /* Something is wrong.  */
@@ -1701,6 +1704,9 @@ open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
          else if (!VALID_ELF_ABIVERSION (ehdr->e_ident[EI_OSABI],
                                          ehdr->e_ident[EI_ABIVERSION]))
            errstring = N_("ELF file ABI version invalid");
+         else if (memcmp (&ehdr->e_ident[EI_PAD], &expected[EI_PAD],
+                          EI_NIDENT - EI_PAD) != 0)
+           errstring = N_("nonzero padding in e_ident");
          else
            /* Otherwise we don't know what went wrong.  */
            errstring = N_("internal error");