From patchwork Thu Mar 20 13:24:11 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 14023983 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E9A2C2AE99 for ; Thu, 20 Mar 2025 13:24:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742477066; cv=none; b=b+Dd2Va2UW9GneSTCrlDat4WAQkiFENPL/of5NqiKxg66ZSquTdCBZHufwF25Nm62IND7VPDealHSFUMP8zg+QEn2BnXkCtfI+y0Dnc1JFT+mWzhM/FIv1pctOCSigluA8wjMAJe+bF7fK22G9i6YdMuFh3z6uVJvrUu5gcFXnQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742477066; c=relaxed/simple; bh=2oPuMKXAnppK07WHh02sLh41hDtkPLKu83E2A4l+cPw=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=SeuxGYnFa55eFRLBYHSV+m6PSvVMa52Jgh7OEk3BpLPfzptbnaFhdgRLfSTmXDMJBEf+MoJ8SzLEvS24bJ3igHee/zZSuIZf2f/7yH20ED73CyGkT9ZPHgPy0+nJUBlcBkHy6xudF8Ni0c8QS8ZPt6pyEJXy7Gc6DBXt8sexVcU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q6OXomrq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q6OXomrq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D10D6C4CEEC; Thu, 20 Mar 2025 13:24:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742477065; bh=2oPuMKXAnppK07WHh02sLh41hDtkPLKu83E2A4l+cPw=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Q6OXomrq/fFmUUszs/ghr8EBPk2w83o8eoMKIxd8OC98cgHtME/6+T17hiA341d5j zIyr4aHtK1mOoc4boUSPGaPY+7+XQepRZIKR7y4Yk3Vc7HrVFEJ4kd44VhGALaC25b uoJ/PHO7vxRypi6PVedI7yhv5bVZyH39+8cv5aJvaCFQBqCxMg5+GBGCtR8WihhHaC IlD+QEdNf8vF5izCtLRJQITJhjghnAwwMehPg+NVZfq8oesF4ULJM+zatXlgoAp4dK ovpSC/LuUTFcELFG/XtLTffCKBKugZx6XkelMN66g/8JJz5woZfqB7LgXmXuL0RCIh yV7FG3xNfvJ9A== From: Christian Brauner Date: Thu, 20 Mar 2025 14:24:11 +0100 Subject: [PATCH v4 4/4] selftests/pidfd: third test for multi-threaded exec polling Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250320-work-pidfs-thread_group-v4-4-da678ce805bf@kernel.org> References: <20250320-work-pidfs-thread_group-v4-0-da678ce805bf@kernel.org> In-Reply-To: <20250320-work-pidfs-thread_group-v4-0-da678ce805bf@kernel.org> To: Oleg Nesterov Cc: linux-fsdevel@vger.kernel.org, Jeff Layton , Lennart Poettering , Daan De Meyer , Mike Yuan , Christian Brauner X-Mailer: b4 0.15-dev-42535 X-Developer-Signature: v=1; a=openpgp-sha256; l=5712; i=brauner@kernel.org; h=from:subject:message-id; bh=2oPuMKXAnppK07WHh02sLh41hDtkPLKu83E2A4l+cPw=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMaTfEftnE+q4koP90KxMn4RtnxwOa3Lefcree1Dpw9tsJ pmHCySMO0pZGMS4GGTFFFkc2k3C5ZbzVGw2ytSAmcPKBDKEgYtTACbypJaR4dbLSxofO+9pPN7F eqJ7Ssv7wLgfIssvi2pq32GfyiCzdz4jw50fzne8dz+47njzt+N63fgNJwwsJy9fNGH28rjrHnG PVbgA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Ensure that during a multi-threaded exec and premature thread-group leader exit no exit notification is generated. Signed-off-by: Christian Brauner --- tools/testing/selftests/pidfd/pidfd_info_test.c | 147 ++++++++++++++++++++++++ 1 file changed, 147 insertions(+) diff --git a/tools/testing/selftests/pidfd/pidfd_info_test.c b/tools/testing/selftests/pidfd/pidfd_info_test.c index 4169780c9e55..1758a1b0457b 100644 --- a/tools/testing/selftests/pidfd/pidfd_info_test.c +++ b/tools/testing/selftests/pidfd/pidfd_info_test.c @@ -542,4 +542,151 @@ TEST_F(pidfd_info, thread_group_exec) EXPECT_EQ(close(pidfd_thread), 0); } +static void *pidfd_info_thread_exec_sane(void *arg) +{ + pid_t pid_thread = gettid(); + int ipc_socket = *(int *)arg; + + /* Inform the grand-parent what the tid of this thread is. */ + if (write_nointr(ipc_socket, &pid_thread, sizeof(pid_thread)) != sizeof(pid_thread)) + return NULL; + + if (read_nointr(ipc_socket, &pid_thread, sizeof(pid_thread)) != sizeof(pid_thread)) + return NULL; + + close(ipc_socket); + + sys_execveat(AT_FDCWD, "pidfd_exec_helper", NULL, NULL, 0); + return NULL; +} + +TEST_F(pidfd_info, thread_group_exec_thread) +{ + pid_t pid_leader, pid_poller, pid_thread; + pthread_t thread; + int nevents, pidfd_leader, pidfd_leader_thread, pidfd_thread, ret; + int ipc_sockets[2]; + struct pollfd fds = {}; + struct pidfd_info info = { + .mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT, + }; + + ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + EXPECT_EQ(ret, 0); + + pid_leader = create_child(&pidfd_leader, 0); + EXPECT_GE(pid_leader, 0); + + if (pid_leader == 0) { + close(ipc_sockets[0]); + + /* The thread will outlive the thread-group leader. */ + if (pthread_create(&thread, NULL, pidfd_info_thread_exec_sane, &ipc_sockets[1])) + syscall(__NR_exit, EXIT_FAILURE); + + /* + * Pause the thread-group leader. It will be killed once + * the subthread execs. + */ + pause(); + syscall(__NR_exit, EXIT_SUCCESS); + } + + /* Retrieve the tid of the thread. */ + EXPECT_EQ(close(ipc_sockets[1]), 0); + ASSERT_EQ(read_nointr(ipc_sockets[0], &pid_thread, sizeof(pid_thread)), sizeof(pid_thread)); + + /* Opening a thread as a PIDFD_THREAD must succeed. */ + pidfd_thread = sys_pidfd_open(pid_thread, PIDFD_THREAD); + ASSERT_GE(pidfd_thread, 0); + + /* Open a thread-specific pidfd for the thread-group leader. */ + pidfd_leader_thread = sys_pidfd_open(pid_leader, PIDFD_THREAD); + ASSERT_GE(pidfd_leader_thread, 0); + + pid_poller = fork(); + ASSERT_GE(pid_poller, 0); + if (pid_poller == 0) { + /* + * The subthread will now exec. The struct pid of the old + * thread-group leader will be assumed by the subthread which + * becomes the new thread-group leader. So no exit notification + * must be generated. Wait for 5 seconds and call it a success + * if no notification has been received. + */ + fds.events = POLLIN; + fds.fd = pidfd_leader_thread; + nevents = poll(&fds, 1, 10000 /* wait 5 seconds */); + if (nevents != 0) + _exit(EXIT_FAILURE); + if (fds.revents & POLLIN) + _exit(EXIT_FAILURE); + if (fds.revents & POLLHUP) + _exit(EXIT_FAILURE); + _exit(EXIT_SUCCESS); + } + + /* Now that we've opened a thread-specific pidfd the thread can exec. */ + ASSERT_EQ(write_nointr(ipc_sockets[0], &pid_thread, sizeof(pid_thread)), sizeof(pid_thread)); + EXPECT_EQ(close(ipc_sockets[0]), 0); + ASSERT_EQ(wait_for_pid(pid_poller), 0); + + /* Wait until the kernel has SIGKILLed the thread. */ + fds.events = POLLHUP; + fds.fd = pidfd_thread; + nevents = poll(&fds, 1, -1); + ASSERT_EQ(nevents, 1); + /* The thread has been reaped. */ + ASSERT_TRUE(!!(fds.revents & POLLHUP)); + + /* Retrieve thread-specific exit info from pidfd. */ + ASSERT_EQ(ioctl(pidfd_thread, PIDFD_GET_INFO, &info), 0); + ASSERT_FALSE(!!(info.mask & PIDFD_INFO_CREDS)); + ASSERT_TRUE(!!(info.mask & PIDFD_INFO_EXIT)); + /* + * While the kernel will have SIGKILLed the whole thread-group + * during exec it will cause the individual threads to exit + * cleanly. + */ + ASSERT_TRUE(WIFEXITED(info.exit_code)); + ASSERT_EQ(WEXITSTATUS(info.exit_code), 0); + + /* + * The thread-group leader is still alive, the thread has taken + * over its struct pid and thus its pid number. + */ + info.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT; + ASSERT_EQ(ioctl(pidfd_leader, PIDFD_GET_INFO, &info), 0); + ASSERT_TRUE(!!(info.mask & PIDFD_INFO_CREDS)); + ASSERT_FALSE(!!(info.mask & PIDFD_INFO_EXIT)); + ASSERT_EQ(info.pid, pid_leader); + + /* Take down the thread-group leader. */ + EXPECT_EQ(sys_pidfd_send_signal(pidfd_leader, SIGKILL, NULL, 0), 0); + + /* + * Afte the exec we're dealing with an empty thread-group so now + * we must see an exit notification on the thread-specific pidfd + * for the thread-group leader as there's no subthread that can + * revive the struct pid. + */ + fds.events = POLLIN; + fds.fd = pidfd_leader_thread; + nevents = poll(&fds, 1, -1); + ASSERT_EQ(nevents, 1); + ASSERT_TRUE(!!(fds.revents & POLLIN)); + ASSERT_FALSE(!!(fds.revents & POLLHUP)); + + EXPECT_EQ(sys_waitid(P_PIDFD, pidfd_leader, NULL, WEXITED), 0); + + /* Retrieve exit information for the thread-group leader. */ + info.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT; + ASSERT_EQ(ioctl(pidfd_leader, PIDFD_GET_INFO, &info), 0); + ASSERT_FALSE(!!(info.mask & PIDFD_INFO_CREDS)); + ASSERT_TRUE(!!(info.mask & PIDFD_INFO_EXIT)); + + EXPECT_EQ(close(pidfd_leader), 0); + EXPECT_EQ(close(pidfd_thread), 0); +} + TEST_HARNESS_MAIN