linux-hardening - Re: [PATCH] selftests/memfd: fix test

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Date:   Fri, 14 Apr 2023 14:23:33 +0800
From:   Yujie Liu <yujie.liu@...el.com>
To:     <jeffxu@...omium.org>
CC:     <skhan@...uxfoundation.org>, <keescook@...omium.org>,
        <akpm@...ux-foundation.org>, <dmitry.torokhov@...il.com>,
        <dverkamp@...omium.org>, <hughd@...gle.com>, <jeffxu@...gle.com>,
        <jorgelo@...omium.org>, <linux-kernel@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>, <linux-mm@...ck.org>,
        <jannh@...gle.com>, <linux-hardening@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] selftests/memfd: fix test_sysctl

On Fri, Apr 14, 2023 at 02:28:01AM +0000, jeffxu@...omium.org wrote:
> From: Jeff Xu <jeffxu@...gle.com>
> 
> sysctl memfd_noexec is pid-namespaced, non-reservable,
> and inherent to the child process.
> Moving the inherence test from init ns to child ns, so
> init ns can keep the default value.
> 
> Signed-off-by: Jeff Xu <jeffxu@...gle.com>
> Reported-by: kernel test robot <yujie.liu@...el.com>
> Link: https://lore.kernel.org/oe-lkp/202303312259.441e35db-yujie.liu@intel.com

The reported issue is gone after applying this patch. Thanks.

Tested-by: Yujie Liu <yujie.liu@...el.com>

=========================================================================================
compiler/group/kconfig/rootfs/tbox_group/testcase:
  gcc-11/group-02/x86_64-rhel-8.3-kselftests/debian-12-x86_64-20220629.cgz/lkp-skl-d06/kernel-selftests

commit:
  c4f75bc8bd6b3 ("mm/memfd: add write seals when apply SEAL_EXEC to executable memfd")
  11f75a01448f1 ("selftests/memfd: add tests for MFD_NOEXEC_SEAL MFD_EXEC")
  395874d592d77 ("selftests/memfd: fix test_sysctl")

c4f75bc8bd6b3d62 11f75a01448f1b7a739e75dbd8f 395874d592d775d999d18ef9cae
---------------- --------------------------- ---------------------------
       fail:runs  %reproduction    fail:runs  %reproduction    fail:runs
           |             |             |             |             |
           :6          233%          14:20           0%            :5     kernel-selftests.memfd.run_fuse_test.sh.fail

> ---
>  tools/testing/selftests/memfd/memfd_test.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
> index ae71f15f790d..dba0e8ba002f 100644
> --- a/tools/testing/selftests/memfd/memfd_test.c
> +++ b/tools/testing/selftests/memfd/memfd_test.c
> @@ -43,6 +43,9 @@
>   */
>  static size_t mfd_def_size = MFD_DEF_SIZE;
>  static const char *memfd_str = MEMFD_STR;
> +static pid_t spawn_newpid_thread(unsigned int flags, int (*fn)(void *));
> +static int newpid_thread_fn2(void *arg);
> +static void join_newpid_thread(pid_t pid);
>  
>  static ssize_t fd2name(int fd, char *buf, size_t bufsize)
>  {
> @@ -1111,6 +1114,7 @@ static void test_noexec_seal(void)
>  static void test_sysctl_child(void)
>  {
>  	int fd;
> +	int pid;
>  
>  	printf("%s sysctl 0\n", memfd_str);
>  	sysctl_assert_write("0");
> @@ -1129,6 +1133,10 @@ static void test_sysctl_child(void)
>  			    mfd_def_size,
>  			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
>  
> +	printf("%s child ns\n", memfd_str);
> +	pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn2);
> +	join_newpid_thread(pid);
> +
>  	mfd_assert_mode(fd, 0666);
>  	mfd_assert_has_seals(fd, F_SEAL_EXEC);
>  	mfd_fail_chmod(fd, 0777);
> @@ -1206,12 +1214,6 @@ static void test_sysctl(void)
>  	int pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn);
>  
>  	join_newpid_thread(pid);
> -
> -	printf("%s child ns\n", memfd_str);
> -	sysctl_assert_write("1");
> -
> -	pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn2);
> -	join_newpid_thread(pid);
>  }
>  
>  /*
> -- 
> 2.40.0.577.gac1e443424-goog
>