[v5,03/22] elf: Do not fail for failed dlopem on audit modules (BZ #28061)

  The dl_main() sets the LM_ID_BASE to RT_ADD just before starting to
add load new shared objects.  The state is set to R_CONSISTENT just
after all objects are loaded.

However if a audit modules tries to dlmopen() an inexistent module,
the _dl_open() will assert that the namespace is in an inconsistent
state.

This is different than dlopen(), since first it will not use
LM_ID_BASE and second _dl_map_object_from_fd() is the sole responsible
to set and reset the r_state value.

So the assert() on _dl_open() can not really see if the state is
consistent since it is _dt_main() that reset is.  This patch removes
the assert.

Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
---
 elf/Makefile         |  5 ++++
 elf/dl-open.c        |  2 --
 elf/tst-audit19.c    | 25 +++++++++++++++++++
 elf/tst-auditmod19.c | 57 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 87 insertions(+), 2 deletions(-)
 create mode 100644 elf/tst-audit19.c
 create mode 100644 elf/tst-auditmod19.c
  

On Tue, Nov 9, 2021 at 10:35 AM Adhemerval Zanella via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> The dl_main() sets the LM_ID_BASE to RT_ADD just before starting to
> add load new shared objects.  The state is set to R_CONSISTENT just
> after all objects are loaded.

Did you mean dlmopen in subject?

> However if a audit modules tries to dlmopen() an inexistent module,
> the _dl_open() will assert that the namespace is in an inconsistent
> state.
>
> This is different than dlopen(), since first it will not use
> LM_ID_BASE and second _dl_map_object_from_fd() is the sole responsible
> to set and reset the r_state value.
>
> So the assert() on _dl_open() can not really see if the state is
> consistent since it is _dt_main() that reset is.  This patch removes
> the assert.
>
> Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
> ---
>  elf/Makefile         |  5 ++++
>  elf/dl-open.c        |  2 --
>  elf/tst-audit19.c    | 25 +++++++++++++++++++
>  elf/tst-auditmod19.c | 57 ++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 87 insertions(+), 2 deletions(-)
>  create mode 100644 elf/tst-audit19.c
>  create mode 100644 elf/tst-auditmod19.c
>
> diff --git a/elf/Makefile b/elf/Makefile
> index bd1a0f79b4..96db0b4322 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -226,6 +226,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
>          tst-dlopenfail-2 \
>          tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen \
>          tst-audit18a tst-audit18b \
> +        tst-audit19 \
>          tst-single_threaded tst-single_threaded-pthread \
>          tst-tls-ie tst-tls-ie-dlmopen argv0test \
>          tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
> @@ -315,6 +316,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
>                 tst-unique2mod1 tst-unique2mod2 \
>                 tst-auditmod9a tst-auditmod9b \
>                 tst-auditmod18a tst-auditmod18b tst-audit18bmod \
> +               tst-auditmod19 \
>                 $(if $(CXX),tst-unique3lib tst-unique3lib2 tst-unique4lib \
>                   tst-nodelete-uniquemod tst-nodelete-rtldmod \
>                   tst-nodelete-zmod \
> @@ -1560,6 +1562,9 @@ $(objpfx)tst-audit18b.out: $(objpfx)tst-auditmod18b.so
>  $(objpfx)tst-audit18b: $(objpfx)tst-audit18bmod.so
>  tst-audit18b-ARGS = -- $(host-test-program-cmd)
>
> +$(objpfx)tst-audit19.out: $(objpfx)tst-auditmod19.so
> +tst-audit19-ENV = LD_AUDIT=$(objpfx)tst-auditmod19.so
> +
>  # tst-sonamemove links against an older implementation of the library.
>  LDFLAGS-tst-sonamemove-linkmod1.so = \
>    -Wl,--version-script=tst-sonamemove-linkmod1.map \
> diff --git a/elf/dl-open.c b/elf/dl-open.c
> index 6ea5dd2457..00f6d8cfcc 100644
> --- a/elf/dl-open.c
> +++ b/elf/dl-open.c
> @@ -932,8 +932,6 @@ no more namespaces available for dlmopen()"));
>              the flag here.  */
>         }
>
> -      assert (_dl_debug_update (args.nsid)->r_state == RT_CONSISTENT);
> -
>        /* Release the lock.  */
>        __rtld_lock_unlock_recursive (GL(dl_load_lock));
>
> diff --git a/elf/tst-audit19.c b/elf/tst-audit19.c
> new file mode 100644
> index 0000000000..6f39ccee86
> --- /dev/null
> +++ b/elf/tst-audit19.c
> @@ -0,0 +1,25 @@
> +/* Check dlopen failure on audit modules.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +static int
> +do_test (void)
> +{
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/elf/tst-auditmod19.c b/elf/tst-auditmod19.c
> new file mode 100644
> index 0000000000..c57e50ee4e
> --- /dev/null
> +++ b/elf/tst-auditmod19.c
> @@ -0,0 +1,57 @@
> +/* Check dlopen failure on audit modules.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <dlfcn.h>
> +#include <link.h>
> +#include <stdlib.h>
> +
> +unsigned int
> +la_version (unsigned int v)
> +{
> +  return LAV_CURRENT;
> +}
> +
> +static void
> +check (void)
> +{
> +  {
> +    void *mod = dlopen ("nonexistent.so", RTLD_NOW);
> +    if (mod != NULL)
> +      abort ();
> +  }
> +
> +  {
> +    void *mod = dlmopen (LM_ID_BASE, "nonexistent.so", RTLD_NOW);
> +    if (mod != NULL)
> +      abort ();
> +  }
> +}
> +
> +void
> +la_activity (uintptr_t *cookie, unsigned int flag)
> +{
> +  if (flag != LA_ACT_CONSISTENT)
> +    return;
> +  check ();
> +}
> +
> +void
> +la_preinit (uintptr_t *cookie)
> +{
> +  check ();
> +}
> --
> 2.32.0
>
  

* Adhemerval Zanella:

> So the assert() on _dl_open() can not really see if the state is
> consistent since it is _dt_main() that reset is.  This patch removes
> the assert.

H.J. also mentioned the dlmopen typo.  “since it is _dt_main() that
reset is” seems to have multiple typos, too.

Patch itself looks okay.

Thanks,
Florian
  

On 09/11/2021 15:51, H.J. Lu wrote:
> On Tue, Nov 9, 2021 at 10:35 AM Adhemerval Zanella via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>>
>> The dl_main() sets the LM_ID_BASE to RT_ADD just before starting to
>> add load new shared objects.  The state is set to R_CONSISTENT just
>> after all objects are loaded.
> 
> Did you mean dlmopen in subject?

Yes, I have fixed it.
  

On 10/11/2021 11:00, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> So the assert() on _dl_open() can not really see if the state is
>> consistent since it is _dt_main() that reset is.  This patch removes
>> the assert.
> 
> H.J. also mentioned the dlmopen typo.  “since it is _dt_main() that
> reset is” seems to have multiple typos, too.

Ack.

> 
> Patch itself looks okay.