elf: Call __libc_early_init for reused namespaces (bug 29528)

  libc_map is never reset to NULL, neither during dlclose nor on a
dlopen call which reuses the namespace structure.  As a result, if a
namespace is reused, its libc is not initialized properly.  The most
visible result is a crash in the <ctype.h> functions.

To prevent similar bugs on namespace reuse from surfacing,
unconditionally initialize the chosen namespace to zero using memset.

Tested on i686-linux-gnu and x86_64-linux-gnu.  Built with
build-many-glibcs.py.

---
 elf/Makefile                 |  7 +++++++
 elf/dl-open.c                | 13 +++++++-----
 elf/tst-dlmopen-twice-mod1.c | 37 ++++++++++++++++++++++++++++++++
 elf/tst-dlmopen-twice-mod2.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
 elf/tst-dlmopen-twice.c      | 34 ++++++++++++++++++++++++++++++
 5 files changed, 136 insertions(+), 5 deletions(-)


base-commit: 5ecc98241229d494aaad23a4a3fe106fe11e1f40
  

On Fri, Aug 26, 2022 at 5:46 AM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> libc_map is never reset to NULL, neither during dlclose nor on a
> dlopen call which reuses the namespace structure.  As a result, if a
> namespace is reused, its libc is not initialized properly.  The most
> visible result is a crash in the <ctype.h> functions.
>
> To prevent similar bugs on namespace reuse from surfacing,
> unconditionally initialize the chosen namespace to zero using memset.
>
> Tested on i686-linux-gnu and x86_64-linux-gnu.  Built with
> build-many-glibcs.py.
>
> ---
>  elf/Makefile                 |  7 +++++++
>  elf/dl-open.c                | 13 +++++++-----
>  elf/tst-dlmopen-twice-mod1.c | 37 ++++++++++++++++++++++++++++++++
>  elf/tst-dlmopen-twice-mod2.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
>  elf/tst-dlmopen-twice.c      | 34 ++++++++++++++++++++++++++++++
>  5 files changed, 136 insertions(+), 5 deletions(-)
>
> diff --git a/elf/Makefile b/elf/Makefile
> index 3928a08787..008770bfaf 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -410,6 +410,7 @@ tests += \
>    tst-dlmopen4 \
>    tst-dlmopen-dlerror \
>    tst-dlmopen-gethostbyname \
> +  tst-dlmopen-twice \
>    tst-dlopenfail \
>    tst-dlopenfail-2 \
>    tst-dlopenrpath \
> @@ -839,6 +840,8 @@ modules-names += \
>    tst-dlmopen1mod \
>    tst-dlmopen-dlerror-mod \
>    tst-dlmopen-gethostbyname-mod \
> +  tst-dlmopen-twice-mod1 \
> +  tst-dlmopen-twice-mod2 \
>    tst-dlopenfaillinkmod \
>    tst-dlopenfailmod1 \
>    tst-dlopenfailmod2 \
> @@ -2976,3 +2979,7 @@ $(objpfx)tst-audit-tlsdesc.out: $(objpfx)tst-auditmod-tlsdesc.so
>  tst-audit-tlsdesc-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so
>  $(objpfx)tst-audit-tlsdesc-dlopen.out: $(objpfx)tst-auditmod-tlsdesc.so
>  tst-audit-tlsdesc-dlopen-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so
> +
> +$(objpfx)tst-dlmopen-twice.out: \
> +  $(objpfx)tst-dlmopen-twice-mod1.so \
> +  $(objpfx)tst-dlmopen-twice-mod2.so
> diff --git a/elf/dl-open.c b/elf/dl-open.c
> index a23e65926b..46e8066fd8 100644
> --- a/elf/dl-open.c
> +++ b/elf/dl-open.c
> @@ -844,11 +844,14 @@ _dl_open (const char *file, int mode, const void *caller_dlopen, Lmid_t nsid,
>           _dl_signal_error (EINVAL, file, NULL, N_("\
>  no more namespaces available for dlmopen()"));
>         }
> -      else if (nsid == GL(dl_nns))
> -       {
> -         __rtld_lock_initialize (GL(dl_ns)[nsid]._ns_unique_sym_table.lock);
> -         ++GL(dl_nns);
> -       }
> +
> +      if (nsid == GL(dl_nns))
> +       ++GL(dl_nns);
> +
> +      /* Initialize the new namespace.  Most members are
> +        zero-initialized, only the lock needs special treatment.  */
> +      memset (&GL(dl_ns)[nsid], 0, sizeof (GL(dl_ns)[nsid]));
> +      __rtld_lock_initialize (GL(dl_ns)[nsid]._ns_unique_sym_table.lock);
>
>        _dl_debug_update (nsid)->r_state = RT_CONSISTENT;
>      }
> diff --git a/elf/tst-dlmopen-twice-mod1.c b/elf/tst-dlmopen-twice-mod1.c
> new file mode 100644
> index 0000000000..38a3a5f0ac
> --- /dev/null
> +++ b/elf/tst-dlmopen-twice-mod1.c
> @@ -0,0 +1,37 @@
> +/* Initialization of libc after dlmopen/dlclose/dlmopen (bug 29528).  Module 1.
> +   Copyright (C) 2022 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 <stdio.h>
> +
> +static void __attribute__ ((constructor))
> +init (void)
> +{
> +  puts ("info: tst-dlmopen-twice-mod2.so loaded");

Did you mean tst-dlmopen-twice-mod1.so?

> +  fflush (stdout);
> +}
> +
> +static void __attribute__ ((destructor))
> +fini (void)
> +{
> +  puts ("info: tst-dlmopen-twice-mod2.so about to be unloaded");

Likewise.

> +  fflush (stdout);
> +}
> +
> +/* Large allocation.  The second module does not have this, so it
> +   should load libc at a different address.  */
> +char large_allocate[16 * 1024 * 1024];
> diff --git a/elf/tst-dlmopen-twice-mod2.c b/elf/tst-dlmopen-twice-mod2.c
> new file mode 100644
> index 0000000000..40c6c01f96
> --- /dev/null
> +++ b/elf/tst-dlmopen-twice-mod2.c
> @@ -0,0 +1,50 @@
> +/* Initialization of libc after dlmopen/dlclose/dlmopen (bug 29528).  Module 2.
> +   Copyright (C) 2022 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 <ctype.h>
> +#include <stdio.h>
> +
> +static void __attribute__ ((constructor))
> +init (void)
> +{
> +  puts ("info: tst-dlmopen-twice-mod2.so loaded");
> +  fflush (stdout);
> +}
> +
> +static void __attribute__ ((destructor))
> +fini (void)
> +{
> +  puts ("info: tst-dlmopen-twice-mod2.so about to be unloaded");
> +  fflush (stdout);
> +}
> +
> +int
> +run_check (void)
> +{
> +  puts ("info: about to call isalpha");
> +  fflush (stdout);
> +
> +  volatile char ch = 'a';
> +  if (!isalpha (ch))
> +    {
> +      puts ("error: isalpha ('a') is not true");
> +      fflush (stdout);
> +      return 1;
> +    }
> +  return 0;
> +}
> diff --git a/elf/tst-dlmopen-twice.c b/elf/tst-dlmopen-twice.c
> new file mode 100644
> index 0000000000..449f3c8fa9
> --- /dev/null
> +++ b/elf/tst-dlmopen-twice.c
> @@ -0,0 +1,34 @@
> +/* Initialization of libc after dlmopen/dlclose/dlmopen (bug 29528).  Main.
> +   Copyright (C) 2022 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 <support/xdlfcn.h>
> +#include <support/check.h>
> +
> +static int
> +do_test (void)
> +{
> +  void *handle = xdlmopen (LM_ID_NEWLM, "tst-dlmopen-twice-mod1.so", RTLD_NOW);
> +  xdlclose (handle);
> +  handle = xdlmopen (LM_ID_NEWLM, "tst-dlmopen-twice-mod2.so", RTLD_NOW);
> +  int (*run_check) (void) = xdlsym (handle, "run_check");
> +  TEST_COMPARE (run_check (), 0);
> +  xdlclose (handle);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
>
> base-commit: 5ecc98241229d494aaad23a4a3fe106fe11e1f40
>
  

* H. J. Lu:

>> +static void __attribute__ ((constructor))
>> +init (void)
>> +{
>> +  puts ("info: tst-dlmopen-twice-mod2.so loaded");
>
> Did you mean tst-dlmopen-twice-mod1.so?
>
>> +  fflush (stdout);
>> +}
>> +
>> +static void __attribute__ ((destructor))
>> +fini (void)
>> +{
>> +  puts ("info: tst-dlmopen-twice-mod2.so about to be unloaded");
>
> Likewise.

Thanks, I've sen't a second version.

Florian