This is the mail archive of the libc-alpha@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] Extend BIND_NOW to installed programs with --enable-bind-now


It turns out that static PIE programs benefit from -z now as well (more
RELRO coverage), so the patch below is a small improvement over the
first patch.

Thanks,
Florian

Extend BIND_NOW to installed programs with --enable-bind-now

Commit 2d6ab5df3b675e96ee587ae6a8c2ce004c6b1ba9 ("Document and fix
--enable-bind-now [BZ #21015]") extended BIND_NOW to all installed
shared objects.  This change also covers installed programs.

2019-04-24  Florian Weimer  <fweimer@redhat.com>

	Also enable BIND_NOW for programs if --enable-bind-now.
	* Makeconfig [$(bind-now)] (link-extra-flags): Add -Wl,-z,now.
	(+link-pie): Use $(link-extra-flags).
	(+link-static): Likewise.
	[! $(build-pie-default)] (+link): Likewise.
	* manual/install.texi (Configuring and compiling): Update
	--enable-bind-now description.
	* INSTALL: Regenerated.

diff --git a/INSTALL b/INSTALL
index ddb9e9018d..e137a71169 100644
--- a/INSTALL
+++ b/INSTALL
@@ -176,10 +176,10 @@ if 'CFLAGS' is specified it must enable optimization.  For example:
      protection.
 
 '--enable-bind-now'
-     Disable lazy binding for installed shared objects.  This provides
-     additional security hardening because it enables full RELRO and a
-     read-only global offset table (GOT), at the cost of slightly
-     increased program load times.
+     Disable lazy binding for installed shared objects and programs.
+     This provides additional security hardening because it enables full
+     RELRO and a read-only global offset table (GOT), at the cost of
+     slightly increased program load times.
 
 '--enable-pt_chown'
      The file 'pt_chown' is a helper binary for 'grantpt' (*note
diff --git a/Makeconfig b/Makeconfig
index 07007c9459..89443e9a90 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -398,6 +398,8 @@ endif
 # test modules.
 ifeq ($(bind-now),yes)
 LDFLAGS-lib.so += -Wl,-z,now
+# Extra flags for dynamically linked non-test main programs.
+link-extra-flags += -Wl,-z,now
 endif
 
 # Command to run after every final link (executable or shared object).
@@ -426,7 +428,7 @@ ifndef +link-pie
 	     $(link-extra-libs)
 +link-pie-after-libc = $(+postctorS) $(+postinit)
 define +link-pie
-$(+link-pie-before-libc) $(rtld-LDFLAGS) $(link-libc) $(+link-pie-after-libc)
+$(+link-pie-before-libc) $(rtld-LDFLAGS) $(link-extra-flags) $(link-libc) $(+link-pie-after-libc)
 $(call after-link,$@)
 endef
 define +link-pie-tests
@@ -454,7 +456,7 @@ ifndef +link-static
 	      $(link-extra-libs-static)
 +link-static-after-libc = $(+postctorT) $(+postinit)
 define +link-static
-$(+link-static-before-libc) $(link-libc-static) $(+link-static-after-libc)
+$(+link-static-before-libc) $(link-extra-flags) $(link-libc-static) $(+link-static-after-libc)
 $(call after-link,$@)
 endef
 define +link-static-tests
@@ -485,7 +487,7 @@ else  # not build-pie-default
 	      $(link-extra-libs)
 +link-after-libc = $(+postctor) $(+postinit)
 define +link
-$(+link-before-libc) $(rtld-LDFLAGS) $(link-libc) $(+link-after-libc)
+$(+link-before-libc) $(rtld-LDFLAGS) $(link-extra-flags) $(link-libc) $(+link-after-libc)
 $(call after-link,$@)
 endef
 define +link-tests
diff --git a/NEWS b/NEWS
index 63581b3618..792ffb1ec8 100644
--- a/NEWS
+++ b/NEWS
@@ -47,6 +47,9 @@ Deprecated and removed features, and other changes affecting compatibility:
 * The obsolete RES_INSECURE1 and RES_INSECURE2 option flags for the DNS stub
   resolver have been removed from <resolv.h>.
 
+* With --enable-bind-now, installed programs are now linked with the
+  BIND_NOW flag.
+
 Changes to build and runtime requirements:
 
 * GCC 6.2 or later is required to build the GNU C Library.
diff --git a/manual/install.texi b/manual/install.texi
index a9b8b4974c..29f6b68e25 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -204,10 +204,10 @@ number of routines called directly from assembler are excluded from this
 protection.
 
 @item --enable-bind-now
-Disable lazy binding for installed shared objects.  This provides
-additional security hardening because it enables full RELRO and a
-read-only global offset table (GOT), at the cost of slightly increased
-program load times.
+Disable lazy binding for installed shared objects and programs.  This
+provides additional security hardening because it enables full RELRO
+and a read-only global offset table (GOT), at the cost of slightly
+increased program load times.
 
 @pindex pt_chown
 @findex grantpt


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]