Re: [PATCH 08/19] nptl: Use __pthread_attr_copy in pthread_getattr_default_np (bug 25999)

[Carlos O'Donell <carlos@redhat.com>]

On 5/19/20 6:44 AM, Florian Weimer via Libc-alpha wrote:
> pthread_getattr_default_np needs to make a deep copy.

Agreed, this seems like an oversight regarding the affinity.
I expect not enough programs ever use the kind of setup you run in
the test, but it's still wrong, we should be doing a deep copy.

Tested clean on x86_64 and i686.

OK for master.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  nptl/Makefile                       |  1 +
>  nptl/pthread_getattr_default_np.c   | 12 ++---
>  nptl/tst-pthread-defaultattr-free.c | 78 +++++++++++++++++++++++++++++
>  3 files changed, 82 insertions(+), 9 deletions(-)
>  create mode 100644 nptl/tst-pthread-defaultattr-free.c
> 
> diff --git a/nptl/Makefile b/nptl/Makefile
> index b4aaad0f20..e5686b20ac 100644
> --- a/nptl/Makefile
> +++ b/nptl/Makefile
> @@ -328,6 +328,7 @@ tests = tst-attr2 tst-attr3 tst-default-attr \
>  	tst-thread-affinity-pthread \
>  	tst-thread-affinity-pthread2 \
>  	tst-thread-affinity-sched \
> +	tst-pthread-defaultattr-free \

OK.

>  
>  
>  tests-container =  tst-pthread-getattr
> diff --git a/nptl/pthread_getattr_default_np.c b/nptl/pthread_getattr_default_np.c
> index cce20cbe94..a9665c5df7 100644
> --- a/nptl/pthread_getattr_default_np.c
> +++ b/nptl/pthread_getattr_default_np.c
> @@ -16,20 +16,14 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -#include <errno.h>
> -#include <stdlib.h>
>  #include <pthreadP.h>
>  
>  int
>  pthread_getattr_default_np (pthread_attr_t *out)
>  {
> -  struct pthread_attr *real_out;
> -
> -  real_out = (struct pthread_attr *) out;
> -
>    lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);
> -  *real_out = __default_pthread_attr;
> +  int ret = __pthread_attr_copy (out,
> +                                 (pthread_attr_t *) &__default_pthread_attr);

OK. Locks kept in place, and call to __pthread_attr_copy owns the struct.

>    lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
> -
> -  return 0;
> +  return ret;
>  }
> diff --git a/nptl/tst-pthread-defaultattr-free.c b/nptl/tst-pthread-defaultattr-free.c
> new file mode 100644
> index 0000000000..5a84302380
> --- /dev/null
> +++ b/nptl/tst-pthread-defaultattr-free.c
> @@ -0,0 +1,78 @@
> +/* Test for user-after-free bug in pthread_getattr_default_np (bug 25999).

OK.

> +   Copyright (C) 2020 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 <pthread.h>
> +#include <sched.h>
> +#include <support/check.h>
> +#include <support/xthread.h>
> +
> +static int
> +do_test (void)
> +{
> +  /* This is a typical affinity size.  */
> +  enum { cpu_count = 128 };
> +  cpu_set_t *set = CPU_ALLOC (cpu_count);
> +  size_t set_size = CPU_ALLOC_SIZE (cpu_count);
> +  CPU_ZERO_S (set_size, set);
> +  CPU_SET (1, set);
> +  CPU_SET (3, set);

OK.

> +
> +  /* Apply the affinity mask to the default attribute.  */
> +  pthread_attr_t attr;
> +  xpthread_attr_init (&attr);
> +  TEST_COMPARE (pthread_attr_setaffinity_np (&attr, set_size, set), 0);
> +  TEST_COMPARE (pthread_setattr_default_np (&attr), 0);

OK. Set the default.

> +  xpthread_attr_destroy (&attr);

OK.

> +
> +  /* Read back the default attribute and check affinity mask.  */
> +  pthread_getattr_default_np (&attr);
> +  CPU_ZERO_S (set_size, set);
> +  TEST_COMPARE (pthread_attr_getaffinity_np (&attr, set_size, set), 0);
> +  for (int i = 0; i < cpu_count; ++i)
> +    TEST_COMPARE (!!CPU_ISSET (i, set), i == 1 || i == 3);

OK.

> +
> +
> +  /* Apply a larger CPU affinity mask to the default attribute, to
> +     trigger reallocation.  */
> +  {
> +    cpu_set_t *large_set = CPU_ALLOC (4 * cpu_count);
> +    size_t large_set_size = CPU_ALLOC_SIZE (4 * cpu_count);
> +    CPU_ZERO_S (large_set_size, large_set);
> +    pthread_attr_t large_attr;
> +    xpthread_attr_init (&large_attr);
> +    TEST_COMPARE (pthread_attr_setaffinity_np (&large_attr,
> +                                               large_set_size, large_set), 0);
> +    TEST_COMPARE (pthread_setattr_default_np (&large_attr), 0);

OK.

> +    xpthread_attr_destroy (&large_attr);
> +    CPU_FREE (large_set);
> +  }
> +
> +  /* Read back the default attribute and check affinity mask.  */
> +  CPU_ZERO_S (set_size, set);
> +  TEST_COMPARE (pthread_attr_getaffinity_np (&attr, set_size, set), 0);
> +  for (int i = 0; i < cpu_count; ++i)
> +    TEST_COMPARE (!!CPU_ISSET (i, set), i == 1 || i == 3);
> +  /* Due to bug 25999, the following caused a double-free abort.  */
> +  xpthread_attr_destroy (&attr);

OK.

> +
> +  CPU_FREE (set);
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> 


-- 
Cheers,
Carlos.