Move setproctitle() automatic initialization to its own library

The automatic initialization cannot be part of the main shared library,
because there is no thread-safe way to change the environ global
variable. This is not a problem if the initializaion happens just at
program load time, but becomes one if the shared library is directly or
indirectly dlopen()ed during the execution of the program, which could
have either kept references to the old environ or could change it in
some other thread. This has been observed for example on systems using
Samba NSS modules.

To avoid any other possible fallout, the constructor is split into a
new static library that needs to be linked explicitly into programs
using setproctitle(). As an additional safety measure the pkg-config
linker flags will mark the program as not allowing to be dlopen()ed
so that we avoid the problem described above.

Reported-by: Jan Alexander Steffens (heftig) <jan.steffens@gmail.com>
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=66679

diff --git a/configure.ac b/configure.ac
index a390d0c36775538073fadccf7deeafd2f99aa7f9..dbad6f46e99a086ca5a1f2403f55b86ff8d80dae 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -132,6 +132,7 @@ AC_CONFIG_FILES([
        man/Makefile
        src/Makefile
        src/libbsd.pc
+       src/libbsd-ctor.pc
        src/libbsd-overlay.pc
        test/Makefile
 ])

diff --git a/include/bsd/unistd.h b/include/bsd/unistd.h
index 193dd351a439b356eb756ebeb3b0fdc5d7ef20a0..5dfa605f263054892634aa30f856f0318ce33e8a 100644 (file)
--- a/include/bsd/unistd.h
+++ b/include/bsd/unistd.h
@@ -56,6 +56,10 @@ void *setmode(const char *mode_str);
 
 void closefrom(int lowfd);
 
+/* Compatibility with sendmail implementations. */
+#define initsetproctitle(c, a, e) setproctitle_init((c), (a), (e))
+
+void setproctitle_init(int argc, char *argv[], char *envp[]);
 void setproctitle(const char *fmt, ...);
 
 int getpeereid(int s, uid_t *euid, gid_t *egid);

diff --git a/man/setproctitle.3 b/man/setproctitle.3
index d42498e320e6ba76d53517c33fbe10d1bb5f4981..dd5df592e3371676fa63625d6f8622d56a221d1f 100644 (file)
--- a/man/setproctitle.3
+++ b/man/setproctitle.3
@@ -33,6 +33,8 @@
 .In sys/types.h
 .In bsd/unistd.h
 .Ft void
+.Fn setproctitle_init "int argc" "char *argv[]" "char *envp[]"
+.Ft void
 .Fn setproctitle "const char *fmt" "..."
 .Sh DESCRIPTION
 The
@@ -41,6 +43,15 @@ library routine sets the process title that appears on the
 .Xr ps 1
 command.
 .Pp
+The
+.Fn setproctitle_init
+library routine only needs to be called (before any call to
+.Fn setproctitle
+and with
+.Fn main
+arguments), if the automatic constructor support has not
+been linked in through the libbsd-ctor pkg-config file.
+.Pp
 The title is set from the executable's name, followed by the
 result of a
 .Xr printf 3
@@ -101,6 +112,11 @@ first appeared in
 .Fx 2.2 .
 Other operating systems have
 similar functions.
+.Pp
+The
+.Fn setproctitle_init
+function is a libbsd extension not present on the BSDs, avoid using it
+in portable code.
 .Sh AUTHORS
 .An -nosplit
 .An Peter Wemm Aq peter@FreeBSD.org

diff --git a/src/Makefile.am b/src/Makefile.am
index 96fee3e4aeb70acef34123d2fe4bdcad803eeb0c..46f86346348f3863156ee57f4e0e4bea846f150c 100644 (file)
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -10,6 +10,7 @@ AM_CPPFLAGS = \
 EXTRA_DIST = \
        libbsd.map \
        libbsd.pc.in \
+       libbsd-ctor.pc.in \
        libbsd-overlay.pc.in \
        hash/helper.c \
        $(nil)
@@ -21,10 +22,12 @@ CLEANFILES = \
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = \
        libbsd.pc \
+       libbsd-ctor.pc \
        libbsd-overlay.pc \
        $(nil)
 
 lib_LTLIBRARIES = libbsd.la
+lib_LIBRARIES = libbsd-ctor.a
 
 hash/md5hl.c: $(srcdir)/hash/helper.c
        $(AM_V_at) $(MKDIR_P) hash
@@ -75,6 +78,10 @@ libbsd_la_SOURCES = \
        wcslcpy.c \
        $(nil)
 
+libbsd_ctor_a_SOURCES = \
+       setproctitle_ctor.c \
+       $(nil)
+
 runtimelibdir = $(libdir)
 
 install-exec-hook:

diff --git a/src/libbsd-ctor.pc.in b/src/libbsd-ctor.pc.in
new file mode 100644 (file)
index 0000000..117b823
--- /dev/null
+++ b/src/libbsd-ctor.pc.in
@@ -0,0 +1,12 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: libbsd-ctor
+Description: Automatic constructor functions for libbsd
+Version: @VERSION@
+URL: http://libbsd.freedesktop.org/
+Cflags: -I${includedir}
+Libs: -L${libdir} -Wl,-z,nodlopen -Wl,-u,libbsd_init_func -lbsd-ctor
+Requires: libbsd

diff --git a/src/libbsd.map b/src/libbsd.map
index 4067e2c0e38ee6c328bf796b091281a5dd9c16ad..52df212cd9216e2adea13361d9361844ca2d6af1 100644 (file)
--- a/src/libbsd.map
+++ b/src/libbsd.map
@@ -105,3 +105,8 @@ LIBBSD_0.5 {
     wcslcat;
     wcslcpy;
 } LIBBSD_0.4;
+
+LIBBSD_0.6 {
+    /* Exported to cope with the constructor+dlopen+threads mess. */
+    setproctitle_init;
+} LIBBSD_0.5;

diff --git a/src/setproctitle.c b/src/setproctitle.c
index 7e4b16567e96bfce4bbbb29d5b90c135b7eac6df..305b563455c0c616622d573839261d5252e22b11 100644 (file)
--- a/src/setproctitle.c
+++ b/src/setproctitle.c
@@ -153,8 +153,8 @@ spt_copyargs(int argc, char *argv[])
        return 0;
 }
 
-static void
-spt_init(int argc, char *argv[], char *envp[])
+void
+setproctitle_init(int argc, char *argv[], char *envp[])
 {
        char *base, *end, *nul, *tmp;
        int i, envc, error;
@@ -215,14 +215,6 @@ spt_init(int argc, char *argv[], char *envp[])
        SPT.end  = end;
 }
 
-/*
- * Force spt_init() function into the .init_array section instead of expecting
- * either the compiler to place constructors there or the linker to move them
- * from .ctors to .init_array.
- */
-void (*spt_init_func)(int argc, char *argv[], char *envp[])
-       __attribute__((section(".init_array"))) = spt_init;
-
 #ifndef SPT_MAXTITLE
 #define SPT_MAXTITLE 255
 #endif

diff --git a/src/setproctitle_ctor.c b/src/setproctitle_ctor.c
new file mode 100644 (file)
index 0000000..9360774
--- /dev/null
+++ b/src/setproctitle_ctor.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright © 2013 Guillem Jover <guillem@hadrons.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <unistd.h>
+
+/*
+ * The automatic initialization cannot be part of the main shared library,
+ * because there is no thread-safe way to change the environ global
+ * variable. This is not a problem if the initializaion happens just at
+ * program load time, but becomes one if the shared library is directly or
+ * indirectly dlopen()ed during the execution of the program, which could
+ * have either kept references to the old environ or could change it in
+ * some other thread. This has been observed for example on systems using
+ * Samba NSS modules.
+ *
+ * To avoid any other possible fallout, the constructor is split into a
+ * new static library that needs to be linked explicitly into programs
+ * using setproctitle(). As an additional safety measure the pkg-config
+ * linker flags will mark the program as not allowing to be dlopen()ed
+ * so that we make sure to avoid the problem described above.
+ */
+
+/*
+ * Force setproctitle_init() function into the .init_array section instead of
+ * expecting either the compiler to place constructors there or the linker to
+ * move them from .ctors to .init_array.
+ */
+void (*libbsd_init_func)(int argc, char *argv[], char *envp[])
+       __attribute__((section(".init_array"))) = setproctitle_init;

diff --git a/test/Makefile.am b/test/Makefile.am
index 73a1e911ca88a9a25a4f6df7266152833a0c7181..d0e0f0b71263defa4044ab8c5f947851a6f0dea1 100644 (file)
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -18,6 +18,10 @@ check_PROGRAMS = \
 
 humanize_LDFLAGS = $(top_builddir)/src/libbsd.la
 fgetln_LDFLAGS = $(top_builddir)/src/libbsd.la
-proctitle_LDFLAGS = $(top_builddir)/src/libbsd.la
+proctitle_LDFLAGS = \
+       -Wl,-u,libbsd_init_func \
+       $(top_builddir)/src/libbsd-ctor.a \
+       $(top_builddir)/src/libbsd.la \
+       $(nil)
 
 TESTS = $(check_PROGRAMS)