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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id q30sm13377505pjh.5.2020.03.13.16.07.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2020 16:07:54 -0700 (PDT) Date: Fri, 13 Mar 2020 16:07:53 -0700 From: Kees Cook To: Christian Brauner Cc: gregkh@linuxfoundation.org, tkjos@android.com, linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org, ardb@kernel.org, arve@android.com, hridya@google.com, joel@joelfernandes.org, john.stultz@linaro.org, kernel-team@android.com, linux-kselftest@vger.kernel.org, maco@android.com, naresh.kamboju@linaro.org, shuah@kernel.org Subject: Re: [PATCH v2 2/3] binderfs_test: switch from /dev to a unique per-test mountpoint Message-ID: <202003131607.10FDF99191@keescook> References: <20200312131531.3615556-1-christian.brauner@ubuntu.com> <20200313152420.138777-1-christian.brauner@ubuntu.com> <20200313152420.138777-2-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200313152420.138777-2-christian.brauner@ubuntu.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 13, 2020 at 04:24:19PM +0100, Christian Brauner wrote: > Unprivileged users will be able to create directories in there. The > unprivileged test for /dev wouldn't have worked on most systems. > > Cc: Kees Cook : > Signed-off-by: Christian Brauner Reviewed-by: Kees Cook -Kees > --- > /* v2 */ > - Kees Cook : > - Switch to unique mountpoint through mkdtemp(). > --- > .../filesystems/binderfs/binderfs_test.c | 47 +++++++++---------- > 1 file changed, 23 insertions(+), 24 deletions(-) > > diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > index 0cfca65e095a..818eb49f8125 100644 > --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > @@ -139,29 +139,25 @@ static int __do_binderfs_test(void) > int fd, ret, saved_errno; > size_t len; > ssize_t wret; > - bool keep = false; > struct binderfs_device device = { 0 }; > struct binder_version version = { 0 }; > + char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX", > + device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME]; > > change_to_mountns(); > > - ret = mkdir("/dev/binderfs", 0755); > - if (ret < 0) { > - if (errno != EEXIST) > - ksft_exit_fail_msg( > - "%s - Failed to create binderfs mountpoint\n", > - strerror(errno)); > - > - keep = true; > - } > + if (!mkdtemp(binderfs_mntpt)) > + ksft_exit_fail_msg( > + "%s - Failed to create binderfs mountpoint\n", > + strerror(errno)); > > - ret = mount(NULL, "/dev/binderfs", "binder", 0, 0); > + ret = mount(NULL, binderfs_mntpt, "binder", 0, 0); > if (ret < 0) { > if (errno != ENODEV) > ksft_exit_fail_msg("%s - Failed to mount binderfs\n", > strerror(errno)); > > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > return 1; > } > > @@ -170,7 +166,8 @@ static int __do_binderfs_test(void) > > memcpy(device.name, "my-binder", strlen("my-binder")); > > - fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC); > + snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt); > + fd = open(device_path, O_RDONLY | O_CLOEXEC); > if (fd < 0) > ksft_exit_fail_msg( > "%s - Failed to open binder-control device\n", > @@ -181,7 +178,7 @@ static int __do_binderfs_test(void) > close(fd); > errno = saved_errno; > if (ret < 0) { > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > ksft_exit_fail_msg( > "%s - Failed to allocate new binder device\n", > strerror(errno)); > @@ -194,9 +191,10 @@ static int __do_binderfs_test(void) > /* binder device allocation test passed */ > ksft_inc_pass_cnt(); > > - fd = open("/dev/binderfs/my-binder", O_CLOEXEC | O_RDONLY); > + snprintf(device_path, sizeof(device_path), "%s/my-binder", binderfs_mntpt); > + fd = open(device_path, O_CLOEXEC | O_RDONLY); > if (fd < 0) { > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > ksft_exit_fail_msg("%s - Failed to open my-binder device\n", > strerror(errno)); > } > @@ -206,7 +204,7 @@ static int __do_binderfs_test(void) > close(fd); > errno = saved_errno; > if (ret < 0) { > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > ksft_exit_fail_msg( > "%s - Failed to open perform BINDER_VERSION request\n", > strerror(errno)); > @@ -218,9 +216,9 @@ static int __do_binderfs_test(void) > /* binder transaction with binderfs binder device passed */ > ksft_inc_pass_cnt(); > > - ret = unlink("/dev/binderfs/my-binder"); > + ret = unlink(device_path); > if (ret < 0) { > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > ksft_exit_fail_msg("%s - Failed to delete binder device\n", > strerror(errno)); > } > @@ -228,12 +226,13 @@ static int __do_binderfs_test(void) > /* binder device removal passed */ > ksft_inc_pass_cnt(); > > - ret = unlink("/dev/binderfs/binder-control"); > + snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt); > + ret = unlink(device_path); > if (!ret) { > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > ksft_exit_fail_msg("Managed to delete binder-control device\n"); > } else if (errno != EPERM) { > - keep ? : rmdir_protect_errno("/dev/binderfs"); > + rmdir_protect_errno(binderfs_mntpt); > ksft_exit_fail_msg( > "%s - Failed to delete binder-control device but exited with unexpected error code\n", > strerror(errno)); > @@ -243,8 +242,8 @@ static int __do_binderfs_test(void) > ksft_inc_xfail_cnt(); > > on_error: > - ret = umount2("/dev/binderfs", MNT_DETACH); > - keep ?: rmdir_protect_errno("/dev/binderfs"); > + ret = umount2(binderfs_mntpt, MNT_DETACH); > + rmdir_protect_errno(binderfs_mntpt); > if (ret < 0) > ksft_exit_fail_msg("%s - Failed to unmount binderfs\n", > strerror(errno)); > -- > 2.25.1 > -- Kees Cook