Re: [PATCH] Use libnss_files.so for tests posix/bug-ga2 and resolv/tst-leaks2 [BZ #26821]

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Nov 19, 2020 at 4:32 AM Stefan Liebler via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> The tests posix/bug-ga2-mem and resolv/mtrace-tst-leaks2 are failing on
> fedora 33 as mtrace reports memory leaks.
>
> The /etc/nsswitch.conf differs between
> Fedora 32: hosts:      files dns myhostname
> Fedora 33: hosts:      files resolve [!UNAVAIL=return] myhostname dns
>
> Therefore /lib64/libnss_resolve.so.2 (from systemd) and the dependencies
> libgcc_s.so.1 and libpthread.so.0 are loaded.
>
> Usually all malloc'ed resources from getaddrinfo / gethostbyname are freed
> and the libraries are dlclose'd in nss/nsswitch.c:libc_freeres_fn (free_mem).
> Unfortunately, /lib64/libnss_resolve.so.2 is marked with DF_1_NODELETE.
> As this library is not unmapped, you'll see "Memory not freed".
>
> Therefore those tests are now only rely on libnss_files.so by preparing
> a chroot with all required configuration files and executing the test in
> a subprocess.
>
> This patch also added support for /etc/services and /etc/nsswitch.conf
> in struct support_chroot_configuration.
>
> Note:
> We can't use __nss_configure_lookup as it would lead to not setting up
> nsswitch.c:service_table before calling __getservbyname_r / __gethostbyname_r.
> nsswitch.c:nss_load_library would then add resources to default_table which
> are not freed by nsswitch.c:libc_freeres_fn (free_mem)
> ---
>  posix/Makefile           |  1 +
>  posix/bug-ga2.c          | 68 +++++++++++++++++++++++++++++++++++-----
>  resolv/Makefile          |  1 +
>  resolv/tst-leaks2.c      | 63 +++++++++++++++++++++++++++++++++----
>  support/namespace.h      |  4 +++
>  support/support_chroot.c |  9 +++++-
>  6 files changed, 132 insertions(+), 14 deletions(-)
>
> diff --git a/posix/Makefile b/posix/Makefile
> index 693082ed28..0ef4e7f4be 100644
> --- a/posix/Makefile
> +++ b/posix/Makefile
> @@ -361,6 +361,7 @@ $(objpfx)bug-ga2-mem.out: $(objpfx)bug-ga2.out
>         $(common-objpfx)malloc/mtrace $(objpfx)bug-ga2.mtrace > $@; \
>         $(evaluate-test)
>
> +$(objpfx)bug-ga2: $(libdl)
>  bug-ga2-ENV = MALLOC_TRACE=$(objpfx)bug-ga2.mtrace
>
>  bug-glob2-ENV = MALLOC_TRACE=$(objpfx)bug-glob2.mtrace
> diff --git a/posix/bug-ga2.c b/posix/bug-ga2.c
> index 5ea759b8ce..889f100358 100644
> --- a/posix/bug-ga2.c
> +++ b/posix/bug-ga2.c
> @@ -1,16 +1,46 @@
>  /* Test case by Sam Varshavchik <mrsam@courier-mta.com>.  */
>  #include <mcheck.h>
>  #include <netdb.h>
> -#include <stdio.h>
> +#include <stdlib.h>
>  #include <string.h>
> +#include <dlfcn.h>
> +#include <gnu/lib-names.h>
> +#include <support/check.h>
> +#include <support/namespace.h>
> +#include <support/test-driver.h>
> +#include <support/xunistd.h>
>
> -int
> -main (void)
> +struct support_chroot *chroot_env;
> +
> +static void
> +prepare (int argc, char **argv)
> +{
> +  /* Generate a /etc/nsswitch.conf instead of using __nss_configure_lookup
> +     as it would lead to not setting up nsswitch.c:service_table before calling
> +     __getservbyname_r.  nss_load_library would then add resources to
> +     default_table which are not freed by
> +     nss/nsswitch.c:libc_freeres_fn (free_mem).  */
> +  chroot_env = support_chroot_create
> +    ((struct support_chroot_configuration)
> +     {
> +       .nsswitch_conf =
> +       "services: files\n"
> +       "hosts: files\n",
> +       .host_conf = "multi on\n",
> +       .hosts = "192.0.2.1 www.gnu.org\n",
> +       .services = "http 80/tcp\n"
> +     });
> +}
> +
> +static void
> +subprocess_test (void *closure)
>  {
>    struct addrinfo hints, *res;
>    int i, ret;
>
>    mtrace ();
> +  xchroot (chroot_env->path_chroot);
> +
>    for (i = 0; i < 100; i++)
>      {
>        memset (&hints, 0, sizeof (hints));
> @@ -20,11 +50,35 @@ main (void)
>        ret = getaddrinfo ("www.gnu.org", "http", &hints, &res);
>
>        if (ret)
> -       {
> -         printf ("%s\n", gai_strerror (ret));
> -         return 1;
> -       }
> +       FAIL_EXIT1 ("%s\n", gai_strerror (ret));
> +
>        freeaddrinfo (res);
>      }
> +
> +  /* Ensure that the resources malloc'ed by getaddrinfo are freed by
> +     nss/nsswitch.c:libc_freeres_fn (free_mem).  */
> +  exit (EXIT_SUCCESS);
> +}
> +
> +
> +static int
> +do_test (void)
> +{
> +  support_become_root ();
> +  if (!support_can_chroot ())
> +    return EXIT_UNSUPPORTED;
> +
> +  /* Load the libraries now as those are not available in chroot.  */
> +  if (dlopen (LIBNSS_FILES_SO, RTLD_LAZY) == NULL)
> +    FAIL_EXIT1 ("could not load " LIBNSS_FILES_SO ": %s", dlerror ());
> +

Can you copy the needed shared libraries to chroot?

-- 
H.J.