Add ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA to x86

With copy relocation, address of protected data defined in the shared
library may be external.   When there is a relocation against the
protected data symbol within the shared library, we need to check if we
should skip the definition in the executable copied from the protected
data.  This patch adds ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA and defines
it for x86.  If ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA isn't 0, do_lookup_x
will skip the data definition in the executable from copy reloc.

Cherry-pick from master: 62da1e3b00b51383ffa7efc89d8addda0502e107
	[BZ #17711]
	* elf/dl-lookup.c (do_lookup_x): When UNDEF_MAP is NULL, which
	indicates it is called from do_lookup_x on relocation against
	protected data, skip the data definion in the executable from
	copy reloc.
	(_dl_lookup_symbol_x): Pass ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA,
	instead of ELF_RTYPE_CLASS_PLT, to do_lookup_x for
	EXTERN_PROTECTED_DATA relocation against STT_OBJECT symbol.
	* sysdeps/generic/ldsodefs.h * (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA):
	New.  Defined to 4 if DL_EXTERN_PROTECTED_DATA is defined,
	otherwise to 0.
	* sysdeps/i386/dl-lookupcfg.h (DL_EXTERN_PROTECTED_DATA): New.
	* sysdeps/i386/dl-machine.h (elf_machine_type_class): Set class
	to ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA for R_386_GLOB_DAT.
	* sysdeps/x86_64/dl-lookupcfg.h (DL_EXTERN_PROTECTED_DATA): New.
	* sysdeps/x86_64/dl-machine.h (elf_machine_type_class): Set class
	to ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA for R_X86_64_GLOB_DAT.

6 files changed, 91 insertions, 6 deletions

diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index a58e5bc72a..0d3e3cc40e 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -283,6 +283,59 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
       if (sym != NULL)
 	{
 	found_it:
+	  /* When UNDEF_MAP is NULL, which indicates we are called from
+	     do_lookup_x on relocation against protected data, we skip
+	     the data definion in the executable from copy reloc.  */
+	  if (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
+	      && undef_map == NULL
+	      && map->l_type == lt_executable
+	      && type_class == ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)
+	    {
+	      const ElfW(Sym) *s;
+	      unsigned int i;
+
+#if ! ELF_MACHINE_NO_RELA
+	      if (map->l_info[DT_RELA] != NULL
+		  && map->l_info[DT_RELASZ] != NULL
+		  && map->l_info[DT_RELASZ]->d_un.d_val != 0)
+		{
+		  const ElfW(Rela) *rela
+		    = (const ElfW(Rela) *) D_PTR (map, l_info[DT_RELA]);
+		  unsigned int rela_count
+		    = map->l_info[DT_RELASZ]->d_un.d_val / sizeof (*rela);
+
+		  for (i = 0; i < rela_count; i++, rela++)
+		    if (elf_machine_type_class (ELFW(R_TYPE) (rela->r_info))
+			== ELF_RTYPE_CLASS_COPY)
+		      {
+			s = &symtab[ELFW(R_SYM) (rela->r_info)];
+			if (!strcmp (strtab + s->st_name, undef_name))
+			  goto skip;
+		      }
+		}
+#endif
+#if ! ELF_MACHINE_NO_REL
+	      if (map->l_info[DT_REL] != NULL
+		  && map->l_info[DT_RELSZ] != NULL
+		  && map->l_info[DT_RELSZ]->d_un.d_val != 0)
+		{
+		  const ElfW(Rel) *rel
+		    = (const ElfW(Rel) *) D_PTR (map, l_info[DT_REL]);
+		  unsigned int rel_count
+		    = map->l_info[DT_RELSZ]->d_un.d_val / sizeof (*rel);
+
+		  for (i = 0; i < rel_count; i++, rel++)
+		    if (elf_machine_type_class (ELFW(R_TYPE) (rel->r_info))
+			== ELF_RTYPE_CLASS_COPY)
+		      {
+			s = &symtab[ELFW(R_SYM) (rel->r_info)];
+			if (!strcmp (strtab + s->st_name, undef_name))
+			  goto skip;
+		      }
+		}
+#endif
+	    }
+
 	  switch (__builtin_expect (ELFW(ST_BIND) (sym->st_info), STB_GLOBAL))
 	    {
 	    case STB_WEAK:
@@ -456,6 +509,7 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
 	    }
 	}
 
+skip:
       /* If this current map is the one mentioned in the verneed entry
 	 and we have not found a weak entry, it is a bug.  */
       if (symidx == STN_UNDEF && version != NULL && version->filename != NULL
@@ -806,7 +860,12 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
 	  for (scope = symbol_scope; *scope != NULL; i = 0, ++scope)
 	    if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
 			     &protected_value, *scope, i, version, flags,
-			     skip_map, ELF_RTYPE_CLASS_PLT, NULL) != 0)
+			     skip_map,
+			     (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
+			      && ELFW(ST_TYPE) ((*ref)->st_info) == STT_OBJECT
+			      && type_class == ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)
+			     ? ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
+			     : ELF_RTYPE_CLASS_PLT, NULL) != 0)
 	      break;
 
 	  if (protected_value.s != NULL && protected_value.m != undef_map)
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index ffeb093887..6276df4221 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -108,13 +108,23 @@ typedef struct link_map *lookup_t;
    satisfied by any symbol in the executable.  Some architectures do
    not support copy relocations.  In this case we define the macro to
    zero so that the code for handling them gets automatically optimized
-   out.  */
+   out.  ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA means address of protected
+   data defined in the shared library may be external, i.e., due to copy
+   relocation.  */
 #define ELF_RTYPE_CLASS_PLT 1
 #ifndef DL_NO_COPY_RELOCS
 # define ELF_RTYPE_CLASS_COPY 2
 #else
 # define ELF_RTYPE_CLASS_COPY 0
 #endif
+/* If DL_EXTERN_PROTECTED_DATA is defined, address of protected data
+   defined in the shared library may be external, i.e., due to copy
+   relocation.   */
+#ifdef DL_EXTERN_PROTECTED_DATA
+# define ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA 4
+#else
+# define ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA 0
+#endif
 
 /* ELF uses the PF_x macros to specify the segment permissions, mmap
    uses PROT_xxx.  In most cases the three macros have the values 1, 2,
diff --git a/sysdeps/i386/dl-lookupcfg.h b/sysdeps/i386/dl-lookupcfg.h
index 3fea8b4ab1..a9916b9f3c 100644
--- a/sysdeps/i386/dl-lookupcfg.h
+++ b/sysdeps/i386/dl-lookupcfg.h
@@ -20,6 +20,10 @@
 
 #include_next <dl-lookupcfg.h>
 
+/* Address of protected data defined in the shared library may be
+   external due to copy relocation.   */
+#define DL_EXTERN_PROTECTED_DATA
+
 struct link_map;
 
 extern void internal_function _dl_unmap (struct link_map *map);
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 917550c64f..35ba173a81 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -239,13 +239,17 @@ _dl_start_user:\n\
    TLS variable, so undefined references should not be allowed to
    define the value.
    ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
-   of the main executable's symbols, as for a COPY reloc.  */
+   of the main executable's symbols, as for a COPY reloc.
+   ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA iff TYPE describes relocation may
+   against protected data whose address be external due to copy relocation.
+ */
 # define elf_machine_type_class(type) \
   ((((type) == R_386_JMP_SLOT || (type) == R_386_TLS_DTPMOD32		      \
      || (type) == R_386_TLS_DTPOFF32 || (type) == R_386_TLS_TPOFF32	      \
      || (type) == R_386_TLS_TPOFF || (type) == R_386_TLS_DESC)		      \
     * ELF_RTYPE_CLASS_PLT)						      \
-   | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
+   | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY)			      \
+   | (((type) == R_386_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
 
 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 #define ELF_MACHINE_JMP_SLOT	R_386_JMP_SLOT
diff --git a/sysdeps/x86_64/dl-lookupcfg.h b/sysdeps/x86_64/dl-lookupcfg.h
index 3fea8b4ab1..a9916b9f3c 100644
--- a/sysdeps/x86_64/dl-lookupcfg.h
+++ b/sysdeps/x86_64/dl-lookupcfg.h
@@ -20,6 +20,10 @@
 
 #include_next <dl-lookupcfg.h>
 
+/* Address of protected data defined in the shared library may be
+   external due to copy relocation.   */
+#define DL_EXTERN_PROTECTED_DATA
+
 struct link_map;
 
 extern void internal_function _dl_unmap (struct link_map *map);
diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
index 504c95f320..34f2773e13 100644
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -170,7 +170,10 @@ _dl_start_user:\n\
    TLS variable, so undefined references should not be allowed to
    define the value.
    ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
-   of the main executable's symbols, as for a COPY reloc.  */
+   of the main executable's symbols, as for a COPY reloc.
+   ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA iff TYPE describes relocation may
+   against protected data whose address be external due to copy relocation.
+ */
 #define elf_machine_type_class(type)					      \
   ((((type) == R_X86_64_JUMP_SLOT					      \
      || (type) == R_X86_64_DTPMOD64					      \
@@ -178,7 +181,8 @@ _dl_start_user:\n\
      || (type) == R_X86_64_TPOFF64					      \
      || (type) == R_X86_64_TLSDESC)					      \
     * ELF_RTYPE_CLASS_PLT)						      \
-   | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY))
+   | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY)			      \
+   | (((type) == R_X86_64_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
 
 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 #define ELF_MACHINE_JMP_SLOT	R_X86_64_JUMP_SLOT