Eliminate RTLD_PROTECT_PLT: ld.so is built with -Bsymbolic so the

PLT is empty/unused.  On at least macppc and sparc64, ld.so's attempt
to mprotect its PLT could instead hit its own allocated data and
cause a segfault shortly there after.

While here, take a shot at preventing the same issue with the GOT
by checking for __got_start != __got_end.

reproduction *with ktracing* by afresh1@ provided the key data
ok miod@ deraadt@

5 files changed, 12 insertions, 29 deletions

diff --git a/libexec/ld.so/alpha/archdep.h b/libexec/ld.so/alpha/archdep.h
index 37f70625bf8..44e7f595bf7 100644
--- a/libexec/ld.so/alpha/archdep.h
+++ b/libexec/ld.so/alpha/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.14 2014/04/16 10:52:58 guenther Exp $ */
+/*	$OpenBSD: archdep.h,v 1.15 2014/11/03 17:50:56 guenther Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -41,8 +41,6 @@
 #include "syscall.h"
 #include "util.h"
 
-#define RTLD_PROTECT_PLT
-
 static inline void
 RELOC_REL(Elf64_Rel *r, const Elf64_Sym *s, Elf64_Addr *p, unsigned long v)
 {
diff --git a/libexec/ld.so/loader.c b/libexec/ld.so/loader.c
index c5449df8901..8cc91d2f842 100644
--- a/libexec/ld.so/loader.c
+++ b/libexec/ld.so/loader.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: loader.c,v 1.150 2014/07/10 09:03:01 otto Exp $ */
+/*	$OpenBSD: loader.c,v 1.151 2014/11/03 17:50:56 guenther Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -399,23 +399,14 @@ _dl_boot(const char **argv, char **envp, const long dyn_loff, long *dl_data)
 	{
 		extern char *__got_start;
 		extern char *__got_end;
-#ifdef RTLD_PROTECT_PLT
-		extern char *__plt_start;
-		extern char *__plt_end;
-#endif
 
-		_dl_mprotect((void *)ELF_TRUNC((long)&__got_start, _dl_pagesz),
-		    ELF_ROUND((long)&__got_end,_dl_pagesz) -
-		    ELF_TRUNC((long)&__got_start, _dl_pagesz),
-		    GOT_PERMS);
-
-#ifdef RTLD_PROTECT_PLT
-		/* only for DATA_PLT or BSS_PLT */
-		_dl_mprotect((void *)ELF_TRUNC((long)&__plt_start, _dl_pagesz),
-		    ELF_ROUND((long)&__plt_end,_dl_pagesz) -
-		    ELF_TRUNC((long)&__plt_start, _dl_pagesz),
-		    PROT_READ|PROT_EXEC);
-#endif
+		if (&__got_start != &__got_end) {
+			_dl_mprotect((void *)ELF_TRUNC((long)&__got_start,
+			    _dl_pagesz),
+			    ELF_ROUND((long)&__got_end,_dl_pagesz) -
+			    ELF_TRUNC((long)&__got_start, _dl_pagesz),
+			    GOT_PERMS);
+		}
 	}
 #endif
 
diff --git a/libexec/ld.so/powerpc/archdep.h b/libexec/ld.so/powerpc/archdep.h
index 7bb80dc26c5..8e9733a5af0 100644
--- a/libexec/ld.so/powerpc/archdep.h
+++ b/libexec/ld.so/powerpc/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.15 2014/07/05 12:22:41 miod Exp $ */
+/*	$OpenBSD: archdep.h,v 1.16 2014/11/03 17:50:56 guenther Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -41,8 +41,6 @@
 #include "syscall.h"
 #include "util.h"
 
-#define RTLD_PROTECT_PLT
-
 /*
  *	The following functions are declared inline so they can
  *	be used before bootstrap linking has been finished.
diff --git a/libexec/ld.so/sparc/archdep.h b/libexec/ld.so/sparc/archdep.h
index 509b17c922f..cf3c03743a6 100644
--- a/libexec/ld.so/sparc/archdep.h
+++ b/libexec/ld.so/sparc/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.9 2010/01/02 12:16:35 kettenis Exp $ */
+/*	$OpenBSD: archdep.h,v 1.10 2014/11/03 17:50:56 guenther Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -43,8 +43,6 @@
 #include "syscall.h"
 #include "util.h"
 
-#define RTLD_PROTECT_PLT
-
 static inline void *
 _dl_mmap(void *addr, unsigned int len, unsigned int prot,
 	unsigned int flags, int fd, off_t offset)
diff --git a/libexec/ld.so/sparc64/archdep.h b/libexec/ld.so/sparc64/archdep.h
index 61e32e7e820..27b4036ac18 100644
--- a/libexec/ld.so/sparc64/archdep.h
+++ b/libexec/ld.so/sparc64/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.18 2010/01/02 12:16:35 kettenis Exp $ */
+/*	$OpenBSD: archdep.h,v 1.19 2014/11/03 17:50:56 guenther Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -43,8 +43,6 @@
 #include "syscall.h"
 #include "util.h"
 
-#define RTLD_PROTECT_PLT
-
 static inline void *
 _dl_mmap(void *addr, unsigned int len, unsigned int prot,
 	unsigned int flags, int fd, off_t offset)