Re: [PATCH 3/3] test: add openat2() test for invalid upper 32 bit flag value

From: Richard Guy Briggs <rgb@redhat.com>
To: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Aleksa Sarai <cyphar@cyphar.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org,
	Christian Brauner <christian.brauner@ubuntu.com>
Subject: Re: [PATCH 3/3] test: add openat2() test for invalid upper 32 bit flag value
Date: Fri, 30 Apr 2021 11:24:00 -0400	[thread overview]
Message-ID: <20210430152400.GY3141668@madcap2.tricolour.ca> (raw)
In-Reply-To: <20210423111037.3590242-3-brauner@kernel.org>

On 2021-04-23 13:10, Christian Brauner wrote:
> From: Christian Brauner <christian.brauner@ubuntu.com>
> 
> Test that openat2() rejects unknown flags in the upper 32 bit range.
> 
> Cc: Richard Guy Briggs <rgb@redhat.com>
> Cc: Aleksa Sarai <cyphar@cyphar.com>
> Cc: linux-fsdevel@vger.kernel.org
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
> ---
>  tools/testing/selftests/openat2/openat2_test.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/openat2/openat2_test.c b/tools/testing/selftests/openat2/openat2_test.c
> index 381d874cce99..7379e082a994 100644
> --- a/tools/testing/selftests/openat2/openat2_test.c
> +++ b/tools/testing/selftests/openat2/openat2_test.c
> @@ -155,7 +155,7 @@ struct flag_test {
>  	int err;
>  };
>  
> -#define NUM_OPENAT2_FLAG_TESTS 24
> +#define NUM_OPENAT2_FLAG_TESTS 25
>  
>  void test_openat2_flags(void)
>  {
> @@ -229,6 +229,11 @@ void test_openat2_flags(void)
>  		{ .name = "invalid how.resolve and O_PATH",
>  		  .how.flags = O_PATH,
>  		  .how.resolve = 0x1337, .err = -EINVAL },
> +
> +		/* Invalid flags in the upper 32 bits must be rejected. */
> +		{ .name = "invalid flags (1 << 63)",
> +		  .how.flags = O_RDONLY | (1ULL << 63),
> +		  .how.resolve = 0, .err = -EINVAL },

This doesn't appear to specifically test for flags over 32 bits.  It
appears to test for flags not included in VALID_OPEN_FLAGS.

"1ULL << 2" would accomplish the same thing, as would "1ULL << 31" due
to the unused flags in the bottom 32 bits.

The test appears to be useful, but misnamed.

If a new flag was added at 1ULL << 33, this test wouldn't notice and it
would still get dropped in build_open_flags() when flags gets assigned
to op->open_flags.

>  	};
>  
>  	BUILD_BUG_ON(ARRAY_LEN(tests) != NUM_OPENAT2_FLAG_TESTS);
> -- 
> 2.27.0
> 

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635