Libguestfs - Aug 2021 - [PATCH nbdkit v2 1/2] tests: Invoke MALLOC_CHECK_ correctly and only for glibc

MALLOC_CHECK_ and MALLOC_PERTURB_ environment variables have been
replaced in glibc 2.34 by GLIBC_TUNABLES settings[1][2].  In addition
the new glibc requires that you preload a new library called
libc_malloc_debug.so.0 to get these features.

These features never worked in non-glibc (but the environment
variables are ignored).

Only define MALLOC_* environment variables when we detect glibc < 2.34,
using the ordinary glibc macros[3].

For glibc >= 2.34, use the new library and GLIBC_TUNABLES.  Note this
relies on LD_PRELOAD warning but otherwise not breaking if a preload
library does not exist.

[1]
https://www.gnu.org/software/libc/manual/html_node/Memory-Allocation-Tunables.html
[2] https://sourceware.org/pipermail/libc-alpha/2021-August/129718.html
[3] https://sourceforge.net/p/predef/wiki/Libraries/

Thanks: Eric Blake
---
 configure.ac      | 24 ++++++++++++++++++++++++
 tests/Makefile.am | 23 +++++++++++++++++------
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/configure.ac b/configure.ac
index 9eb9b174..bdb56b37 100644
--- a/configure.ac
+++ b/configure.ac
@@ -569,6 +569,30 @@ AS_IF([test "x$is_windows" = "xyes"],[
 
 AC_SEARCH_LIBS([getaddrinfo], [network socket])
 
+dnl Does this libc have MALLOC_CHECK_ and MALLOC_PERTURB_ (both glibc)
+dnl and does the feature require libc_malloc_debug.so (glibc >= 2.34)?
+AC_MSG_CHECKING([if this is glibc])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#include <limits.h>
+#ifndef __GLIBC__
+#error "not glibc"
+#endif
+        ]])], [is_glibc=yes], [is_glibc=no]
+)
+AC_MSG_RESULT([$is_glibc])
+AM_CONDITIONAL([HAVE_GLIBC], [test "x$is_glibc" = "xyes"])
+
+AC_MSG_CHECKING([if this is glibc >= 2.34])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#include <limits.h>
+#if !defined(__GLIBC__) || __GLIBC__ < 2 || (__GLIBC__ == 2 &&
__GLIBC_MINOR__ < 34)
+#error "not glibc 2.34"
+#endif
+        ]])], [is_glibc_234=yes], [is_glibc_234=no]
+)
+AC_MSG_RESULT([$is_glibc_234])
+AM_CONDITIONAL([HAVE_GLIBC_234], [test "x$is_glibc_234" =
"xyes"])
+
 dnl Check for SELinux socket labelling (optional).
 PKG_CHECK_MODULES([LIBSELINUX], [libselinux], [
     AC_SUBST([LIBSELINUX_CFLAGS])
diff --git a/tests/Makefile.am b/tests/Makefile.am
index a6e27d95..5919187b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -61,21 +61,32 @@ EXTRA_DIST = README.tests
 EXTRA_PROGRAMS  
 # Use the 'direct' backend, and ensure maximum libguestfs debugging.
-#
 # Enable libnbd debugging.
-#
-# Enable malloc-check as a cheap way to find some use-after-free and
-# uninitialized read problems when using glibc, and doesn't affect
-# normal operation or other libc.
 TESTS_ENVIRONMENT = \
 	SRCDIR=$(srcdir) \
 	LIBGUESTFS_ATTACH_METHOD=appliance \
 	LIBGUESTFS_DEBUG=1 \
 	LIBGUESTFS_TRACE=1 \
 	LIBNBD_DEBUG=1 \
+	$(NULL)
+
+# Enable malloc-check as a cheap way to find some use-after-free and
+# uninitialized read problems when using glibc, and doesn't affect
+# normal operation or other libc.
+random = $(shell bash -c 'echo $$(( 1 + (RANDOM & 255) ))')
+if HAVE_GLIBC_234
+TESTS_ENVIRONMENT += \
+
LD_PRELOAD="$${LD_PRELOAD:+"$$LD_PRELOAD:"}$(libdir)/libc_malloc_debug.so.0"
\
+	GLIBC_TUNABLES=glibc.malloc.check=1:glibc.malloc.perturb=$(random) \
+	$(NULL)
+else
+if HAVE_GLIBC
+TESTS_ENVIRONMENT += \
 	MALLOC_CHECK_=1 \
-	MALLOC_PERTURB_=$(shell bash -c 'echo $$(( 1 + (RANDOM & 255) ))')
\
+	MALLOC_PERTURB_=$(random) \
 	$(NULL)
+endif
+endif
 
 if !IS_WINDOWS
 # Ensure we're testing the local copy by running everything through
-- 
2.32.0

On Sun, Aug 22, 2021 at 01:57:15PM +0100, Richard W.M. Jones
wrote:
> MALLOC_CHECK_ and MALLOC_PERTURB_ environment variables have been
> replaced in glibc 2.34 by GLIBC_TUNABLES settings[1][2].  In addition
> the new glibc requires that you preload a new library called
> libc_malloc_debug.so.0 to get these features.
Do we actually require the soname .so.0, or can we get by with the
more generic version-less .so (and thus continue to work when glibc
bumps to .so.1, provided that bump is backwards compatible for our
usage)?
> 
> These features never worked in non-glibc (but the environment
> variables are ignored).
> 
> Only define MALLOC_* environment variables when we detect glibc < 2.34,
> using the ordinary glibc macros[3].
> 
> For glibc >= 2.34, use the new library and GLIBC_TUNABLES.  Note this
> relies on LD_PRELOAD warning but otherwise not breaking if a preload
> library does not exist.
> 
> [1]
https://www.gnu.org/software/libc/manual/html_node/Memory-Allocation-Tunables.html
> [2] https://sourceware.org/pipermail/libc-alpha/2021-August/129718.html
> [3] https://sourceforge.net/p/predef/wiki/Libraries/
> 
> Thanks: Eric Blake
> ---
> +# Enable malloc-check as a cheap way to find some use-after-free and
> +# uninitialized read problems when using glibc, and doesn't affect
> +# normal operation or other libc.
> +random = $(shell bash -c 'echo $$(( 1 + (RANDOM & 255) ))')
> +if HAVE_GLIBC_234
> +TESTS_ENVIRONMENT += \
> +
LD_PRELOAD="$${LD_PRELOAD:+"$$LD_PRELOAD:"}$(libdir)/libc_malloc_debug.so.0"
\
> +	GLIBC_TUNABLES=glibc.malloc.check=1:glibc.malloc.perturb=$(random) \
> +	$(NULL)
-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org