From: Shuah Khan <skhan@linuxfoundation.org>
To: Daniel Verkamp <dverkamp@chromium.org>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Mattias Nissler <mnissler@chromium.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Kees Cook <keescook@chromium.org>,
Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH 3/4] selftests/memfd: add tests for F_SEAL_EXEC
Date: Thu, 7 Apr 2022 14:00:32 -0600 [thread overview]
Message-ID: <6f71a4f3-8f8e-926b-883c-1df630cfc1a0@linuxfoundation.org> (raw)
In-Reply-To: <20220401220834.307660-4-dverkamp@chromium.org>
On 4/1/22 4:08 PM, Daniel Verkamp wrote:
> Basic tests to ensure that user/group/other execute bits cannot be
> changed after applying F_SEAL_EXEC to a memfd.
>
> Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
> ---
> tools/testing/selftests/memfd/memfd_test.c | 80 ++++++++++++++++++++++
> 1 file changed, 80 insertions(+)
>
> diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
> index 94df2692e6e4..fdb0e46e9df9 100644
> --- a/tools/testing/selftests/memfd/memfd_test.c
> +++ b/tools/testing/selftests/memfd/memfd_test.c
> @@ -28,6 +28,10 @@
> #define MFD_DEF_SIZE 8192
> #define STACK_SIZE 65536
>
> +#ifndef F_SEAL_EXEC
> +#define F_SEAL_EXEC 0x0020
> +#endif
> +
> /*
> * Default is not to test hugetlbfs
> */
> @@ -594,6 +598,48 @@ static void mfd_fail_grow_write(int fd)
> }
> }
>
> +static void mfd_assert_mode(int fd, int mode)
> +{
> + struct stat st;
> +
> + if (fstat(fd, &st) < 0) {
> + printf("fstat(%d) failed: %m\n", fd);
Let's print the filename here - just printing fd isn't useful.
> + abort();
> + } else if ((st.st_mode & 07777) != mode) {
> + printf("wrong file mode 0%04o, but expected 0%04o\n",
> + (int)st.st_mode & 07777, mode);
This one doesn't even print fd - same comment here about filename.
> + abort();
> + }
> +}
> +
> +static void mfd_assert_chmod(int fd, int mode)
> +{
> + if (fchmod(fd, mode) < 0) {
> + printf("fchmod(0%04o) failed: %m\n", mode);
Same here.
> + abort();
> + }
> +
> + mfd_assert_mode(fd, mode);
> +}
> +
> +static void mfd_fail_chmod(int fd, int mode)
> +{
> + struct stat st;
> +
> + if (fstat(fd, &st) < 0) {
> + printf("fstat(%d) failed: %m\n", fd);
Same comment about filename
> + abort();
> + }
> +
> + if (fchmod(fd, mode) == 0) {
> + printf("fchmod(0%04o) didn't fail as expected\n");
Same comment about filename
> + abort();
> + }
> +
> + /* verify that file mode bits did not change */
> + mfd_assert_mode(fd, st.st_mode & 07777);
> +}
> +
> static int idle_thread_fn(void *arg)
> {
> sigset_t set;
> @@ -880,6 +926,39 @@ static void test_seal_resize(void)
> close(fd);
> }
>
> +/*
> + * Test SEAL_EXEC
> + * Test that chmod() cannot change x bits after sealing
> + */
> +static void test_seal_exec(void)
> +{
> + int fd;
> +
> + printf("%s SEAL-EXEC\n", memfd_str);
> +
> + fd = mfd_assert_new("kern_memfd_seal_exec",
> + mfd_def_size,
> + MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +
> + mfd_assert_mode(fd, 0777);
> +
> + mfd_assert_chmod(fd, 0644);
> +
> + mfd_assert_has_seals(fd, 0);
> + mfd_assert_add_seals(fd, F_SEAL_EXEC);
> + mfd_assert_has_seals(fd, F_SEAL_EXEC);
> +
> + mfd_assert_chmod(fd, 0600);
> + mfd_fail_chmod(fd, 0777);
> + mfd_fail_chmod(fd, 0670);
> + mfd_fail_chmod(fd, 0605);
> + mfd_fail_chmod(fd, 0700);
> + mfd_fail_chmod(fd, 0100);
> + mfd_assert_chmod(fd, 0666);
> +
> + close(fd);
> +}
> +
> /*
> * Test sharing via dup()
> * Test that seals are shared between dupped FDs and they're all equal.
> @@ -1059,6 +1138,7 @@ int main(int argc, char **argv)
> test_seal_shrink();
> test_seal_grow();
> test_seal_resize();
> + test_seal_exec();
>
> test_share_dup("SHARE-DUP", "");
> test_share_mmap("SHARE-MMAP", "");
>
The rest looks good.
thanks,
-- Shuah
next prev parent reply other threads:[~2022-04-07 20:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220401220834.307660-1-dverkamp@chromium.org>
2022-04-01 22:08 ` [PATCH 4/4] selftests/memfd: add tests for MFD_NOEXEC Daniel Verkamp
2022-04-07 20:03 ` Shuah Khan
[not found] ` <20220401220834.307660-4-dverkamp@chromium.org>
2022-04-07 20:00 ` Shuah Khan [this message]
2022-07-29 6:15 ` [PATCH 3/4] selftests/memfd: add tests for F_SEAL_EXEC Jeff Xu
2022-07-29 6:15 ` [PATCH 4/4] selftests/memfd: add tests for MFD_NOEXEC Jeff Xu
2022-07-29 6:29 ` Jeff Xu
2022-07-29 21:24 ` [PATCH 3/4] selftests/memfd: add tests for F_SEAL_EXEC Jeff Xu
2022-07-29 22:00 ` Jeff Xu
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