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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Memv8GZb; 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="Memv8GZb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9FDEC19424; Mon, 23 Feb 2026 10:45:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771843522; bh=lQWnqJdd5KZDYPYMpsNBRE3B8p6+ExaMxdmOo4pbBnU=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Memv8GZb4zr6FIcBxpeWbbhN6cFLT26CsdQSy2Y7r/iEfl/8ufUMzxRH10kpc2hI/ SfShLdBad4YRiFF4TcbPCfTLA/VJ0MT61XXIjv7e5PGigipuw1kejtLb0iwCN604U6 QAZeTnozMvA9zPHvkkLKoi2Sy42t1ntOh7vGCBaefEo0pwGxafXzOsMmroymqY1zSP RtoY44ziWMi7M9MIJ/MAbJb0OoHCtwW7iGFRfcYN1qVYNJSsO6BmnVHAhSmrcRmok1 IdiNg69z4ybRt9v4pTc3nWAtzpVgRIwGJtREqo9R+lD/tbab245dVCHEK6gHXNBxKL TOp7sHAsLWXAA== From: Christian Brauner Date: Mon, 23 Feb 2026 11:45:00 +0100 Subject: [PATCH v4 3/4] selftests/pidfd: add CLONE_AUTOREAP tests Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260223-work-pidfs-autoreap-v4-3-e393c08c09d1@kernel.org> References: <20260223-work-pidfs-autoreap-v4-0-e393c08c09d1@kernel.org> In-Reply-To: <20260223-work-pidfs-autoreap-v4-0-e393c08c09d1@kernel.org> To: Oleg Nesterov , Jann Horn Cc: Linus Torvalds , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christian Brauner X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=14666; i=brauner@kernel.org; h=from:subject:message-id; bh=lQWnqJdd5KZDYPYMpsNBRE3B8p6+ExaMxdmOo4pbBnU=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWTO0d85td3iyvFPWUdFWzR3cN2ddetE5A3dzNYS4yunZ 19Kss7f0lHKwiDGxSArpsji0G4SLrecp2KzUaYGzBxWJpAhDFycAjAR++MMv1nLTeKui8r8OPr/ rqTERe1kRfmFafv9vedlV4nFaKupXWZkaL8f+mTf0hd1VcVN65OP7Ihz2LhOW/6qu0siz7bC+bn PuQA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Add tests for the new CLONE_AUTOREAP clone3() flag: - autoreap_without_pidfd: CLONE_AUTOREAP without CLONE_PIDFD works (fire-and-forget) - autoreap_rejects_exit_signal: CLONE_AUTOREAP with non-zero exit_signal fails - autoreap_rejects_parent: CLONE_AUTOREAP with CLONE_PARENT fails - autoreap_rejects_thread: CLONE_AUTOREAP with CLONE_THREAD fails - autoreap_basic: child exits, pidfd poll works, PIDFD_GET_INFO returns correct exit code, waitpid() returns -ECHILD - autoreap_signaled: child killed by signal, exit info correct via pidfd - autoreap_reparent: autoreap grandchild reparented to subreaper still auto-reaps - autoreap_multithreaded: autoreap process with sub-threads auto-reaps after last thread exits - autoreap_no_inherit: grandchild forked without CLONE_AUTOREAP becomes a regular zombie Signed-off-by: Christian Brauner --- tools/testing/selftests/pidfd/.gitignore | 1 + tools/testing/selftests/pidfd/Makefile | 2 +- .../testing/selftests/pidfd/pidfd_autoreap_test.c | 507 +++++++++++++++++= ++++ 3 files changed, 509 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/pidfd/.gitignore b/tools/testing/selft= ests/pidfd/.gitignore index 144e7ff65d6a..4cd8ec7fd349 100644 --- a/tools/testing/selftests/pidfd/.gitignore +++ b/tools/testing/selftests/pidfd/.gitignore @@ -12,3 +12,4 @@ pidfd_info_test pidfd_exec_helper pidfd_xattr_test pidfd_setattr_test +pidfd_autoreap_test diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftes= ts/pidfd/Makefile index 764a8f9ecefa..4211f91e9af8 100644 --- a/tools/testing/selftests/pidfd/Makefile +++ b/tools/testing/selftests/pidfd/Makefile @@ -4,7 +4,7 @@ CFLAGS +=3D -g $(KHDR_INCLUDES) $(TOOLS_INCLUDES) -pthread = -Wall TEST_GEN_PROGS :=3D pidfd_test pidfd_fdinfo_test pidfd_open_test \ pidfd_poll_test pidfd_wait pidfd_getfd_test pidfd_setns_test \ pidfd_file_handle_test pidfd_bind_mount pidfd_info_test \ - pidfd_xattr_test pidfd_setattr_test + pidfd_xattr_test pidfd_setattr_test pidfd_autoreap_test =20 TEST_GEN_PROGS_EXTENDED :=3D pidfd_exec_helper =20 diff --git a/tools/testing/selftests/pidfd/pidfd_autoreap_test.c b/tools/te= sting/selftests/pidfd/pidfd_autoreap_test.c new file mode 100644 index 000000000000..9e52a16239ea --- /dev/null +++ b/tools/testing/selftests/pidfd/pidfd_autoreap_test.c @@ -0,0 +1,507 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2026 Christian Brauner + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "pidfd.h" +#include "kselftest_harness.h" + +#ifndef CLONE_AUTOREAP +#define CLONE_AUTOREAP 0x400000000ULL +#endif + +static pid_t create_autoreap_child(int *pidfd) +{ + struct __clone_args args =3D { + .flags =3D CLONE_PIDFD | CLONE_AUTOREAP, + .exit_signal =3D 0, + .pidfd =3D ptr_to_u64(pidfd), + }; + + return sys_clone3(&args, sizeof(args)); +} + +/* + * Test that CLONE_AUTOREAP works without CLONE_PIDFD (fire-and-forget). + */ +TEST(autoreap_without_pidfd) +{ + struct __clone_args args =3D { + .flags =3D CLONE_AUTOREAP, + .exit_signal =3D 0, + }; + pid_t pid; + int ret; + + pid =3D sys_clone3(&args, sizeof(args)); + if (pid < 0 && errno =3D=3D EINVAL) + SKIP(return, "CLONE_AUTOREAP not supported"); + ASSERT_GE(pid, 0); + + if (pid =3D=3D 0) + _exit(0); + + /* + * Give the child a moment to exit and be autoreaped. + * Then verify no zombie remains. + */ + usleep(200000); + ret =3D waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); +} + +/* + * Test that CLONE_AUTOREAP with a non-zero exit_signal fails. + */ +TEST(autoreap_rejects_exit_signal) +{ + struct __clone_args args =3D { + .flags =3D CLONE_PIDFD | CLONE_AUTOREAP, + .exit_signal =3D SIGCHLD, + }; + int pidfd =3D -1; + pid_t pid; + + args.pidfd =3D ptr_to_u64(&pidfd); + + pid =3D sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * Test that CLONE_AUTOREAP with CLONE_PARENT fails. + */ +TEST(autoreap_rejects_parent) +{ + struct __clone_args args =3D { + .flags =3D CLONE_PIDFD | CLONE_AUTOREAP | CLONE_PARENT, + .exit_signal =3D 0, + }; + int pidfd =3D -1; + pid_t pid; + + args.pidfd =3D ptr_to_u64(&pidfd); + pid =3D sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * Test that CLONE_AUTOREAP with CLONE_THREAD fails. + */ +TEST(autoreap_rejects_thread) +{ + struct __clone_args args =3D { + .flags =3D CLONE_PIDFD | CLONE_AUTOREAP | + CLONE_THREAD | CLONE_SIGHAND | + CLONE_VM, + .exit_signal =3D 0, + }; + int pidfd =3D -1; + pid_t pid; + + args.pidfd =3D ptr_to_u64(&pidfd); + + pid =3D sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * Basic test: create an autoreap child, let it exit, verify: + * - pidfd becomes readable (poll returns POLLIN) + * - PIDFD_GET_INFO returns the correct exit code + * - waitpid() returns -1/ECHILD (no zombie) + */ +TEST(autoreap_basic) +{ + struct pidfd_info info =3D { .mask =3D PIDFD_INFO_EXIT }; + int pidfd =3D -1, ret; + struct pollfd pfd; + pid_t pid; + + pid =3D create_autoreap_child(&pidfd); + if (pid < 0 && errno =3D=3D EINVAL) + SKIP(return, "CLONE_AUTOREAP not supported"); + ASSERT_GE(pid, 0); + + if (pid =3D=3D 0) + _exit(42); + + ASSERT_GE(pidfd, 0); + + /* Wait for the child to exit via pidfd poll. */ + pfd.fd =3D pidfd; + pfd.events =3D POLLIN; + ret =3D poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Verify exit info via PIDFD_GET_INFO. */ + ret =3D ioctl(pidfd, PIDFD_GET_INFO, &info); + ASSERT_EQ(ret, 0); + ASSERT_TRUE(info.mask & PIDFD_INFO_EXIT); + /* + * exit_code is in waitpid format: for _exit(42), + * WIFEXITED is true and WEXITSTATUS is 42. + */ + ASSERT_TRUE(WIFEXITED(info.exit_code)); + ASSERT_EQ(WEXITSTATUS(info.exit_code), 42); + + /* Verify no zombie: waitpid should fail with ECHILD. */ + ret =3D waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +/* + * Test that an autoreap child killed by a signal reports + * the correct exit info. + */ +TEST(autoreap_signaled) +{ + struct pidfd_info info =3D { .mask =3D PIDFD_INFO_EXIT }; + int pidfd =3D -1, ret; + struct pollfd pfd; + pid_t pid; + + pid =3D create_autoreap_child(&pidfd); + if (pid < 0 && errno =3D=3D EINVAL) + SKIP(return, "CLONE_AUTOREAP not supported"); + ASSERT_GE(pid, 0); + + if (pid =3D=3D 0) { + pause(); + _exit(1); + } + + ASSERT_GE(pidfd, 0); + + /* Kill the child. */ + ret =3D sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0); + ASSERT_EQ(ret, 0); + + /* Wait for exit via pidfd. */ + pfd.fd =3D pidfd; + pfd.events =3D POLLIN; + ret =3D poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Verify signal info. */ + ret =3D ioctl(pidfd, PIDFD_GET_INFO, &info); + ASSERT_EQ(ret, 0); + ASSERT_TRUE(info.mask & PIDFD_INFO_EXIT); + ASSERT_TRUE(WIFSIGNALED(info.exit_code)); + ASSERT_EQ(WTERMSIG(info.exit_code), SIGKILL); + + /* No zombie. */ + ret =3D waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +/* + * Test autoreap survives reparenting: middle process creates an + * autoreap grandchild, then exits. The grandchild gets reparented + * to us (the grandparent, which is a subreaper). When the grandchild + * exits, it should still be autoreaped - no zombie under us. + */ +TEST(autoreap_reparent) +{ + int ipc_sockets[2], ret; + int pidfd =3D -1; + struct pollfd pfd; + pid_t mid_pid, grandchild_pid; + char buf[32] =3D {}; + + /* Make ourselves a subreaper so reparented children come to us. */ + ret =3D prctl(PR_SET_CHILD_SUBREAPER, 1); + ASSERT_EQ(ret, 0); + + ret =3D socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + ASSERT_EQ(ret, 0); + + mid_pid =3D fork(); + ASSERT_GE(mid_pid, 0); + + if (mid_pid =3D=3D 0) { + /* Middle child: create an autoreap grandchild. */ + int gc_pidfd =3D -1; + + close(ipc_sockets[0]); + + grandchild_pid =3D create_autoreap_child(&gc_pidfd); + if (grandchild_pid < 0) { + write_nointr(ipc_sockets[1], "E", 1); + close(ipc_sockets[1]); + _exit(1); + } + + if (grandchild_pid =3D=3D 0) { + /* Grandchild: wait for signal to exit. */ + close(ipc_sockets[1]); + if (gc_pidfd >=3D 0) + close(gc_pidfd); + pause(); + _exit(0); + } + + /* Send grandchild PID to grandparent. */ + snprintf(buf, sizeof(buf), "%d", grandchild_pid); + write_nointr(ipc_sockets[1], buf, strlen(buf)); + close(ipc_sockets[1]); + if (gc_pidfd >=3D 0) + close(gc_pidfd); + + /* Middle child exits, grandchild gets reparented. */ + _exit(0); + } + + close(ipc_sockets[1]); + + /* Read grandchild's PID. */ + ret =3D read_nointr(ipc_sockets[0], buf, sizeof(buf) - 1); + close(ipc_sockets[0]); + ASSERT_GT(ret, 0); + + if (buf[0] =3D=3D 'E') { + waitpid(mid_pid, NULL, 0); + prctl(PR_SET_CHILD_SUBREAPER, 0); + SKIP(return, "CLONE_AUTOREAP not supported"); + } + + grandchild_pid =3D atoi(buf); + ASSERT_GT(grandchild_pid, 0); + + /* Wait for the middle child to exit. */ + ret =3D waitpid(mid_pid, NULL, 0); + ASSERT_EQ(ret, mid_pid); + + /* + * Now the grandchild is reparented to us (subreaper). + * Open a pidfd for the grandchild and kill it. + */ + pidfd =3D sys_pidfd_open(grandchild_pid, 0); + ASSERT_GE(pidfd, 0); + + ret =3D sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0); + ASSERT_EQ(ret, 0); + + /* Wait for it to exit via pidfd poll. */ + pfd.fd =3D pidfd; + pfd.events =3D POLLIN; + ret =3D poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* + * The grandchild should have been autoreaped even though + * we (the new parent) haven't set SA_NOCLDWAIT. + * waitpid should return -1/ECHILD. + */ + ret =3D waitpid(grandchild_pid, NULL, WNOHANG); + EXPECT_EQ(ret, -1); + EXPECT_EQ(errno, ECHILD); + + close(pidfd); + + /* Clean up subreaper status. */ + prctl(PR_SET_CHILD_SUBREAPER, 0); +} + +static int thread_sock_fd; + +static void *thread_func(void *arg) +{ + /* Signal parent we're running. */ + write_nointr(thread_sock_fd, "1", 1); + + /* Give main thread time to call _exit() first. */ + usleep(200000); + + return NULL; +} + +/* + * Test that an autoreap child with multiple threads is properly + * autoreaped only after all threads have exited. + */ +TEST(autoreap_multithreaded) +{ + struct pidfd_info info =3D { .mask =3D PIDFD_INFO_EXIT }; + int ipc_sockets[2], ret; + int pidfd =3D -1; + struct pollfd pfd; + pid_t pid; + char c; + + ret =3D socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + ASSERT_EQ(ret, 0); + + pid =3D create_autoreap_child(&pidfd); + if (pid < 0 && errno =3D=3D EINVAL) { + close(ipc_sockets[0]); + close(ipc_sockets[1]); + SKIP(return, "CLONE_AUTOREAP not supported"); + } + ASSERT_GE(pid, 0); + + if (pid =3D=3D 0) { + pthread_t thread; + + close(ipc_sockets[0]); + + /* + * Create a sub-thread that outlives the main thread. + * The thread signals readiness, then sleeps. + * The main thread waits briefly, then calls _exit(). + */ + thread_sock_fd =3D ipc_sockets[1]; + pthread_create(&thread, NULL, thread_func, NULL); + pthread_detach(thread); + + /* Wait for thread to be running. */ + usleep(100000); + + /* Main thread exits; sub-thread is still alive. */ + _exit(99); + } + + close(ipc_sockets[1]); + + /* Wait for the sub-thread to signal readiness. */ + ret =3D read_nointr(ipc_sockets[0], &c, 1); + close(ipc_sockets[0]); + ASSERT_EQ(ret, 1); + + /* Wait for the process to fully exit via pidfd poll. */ + pfd.fd =3D pidfd; + pfd.events =3D POLLIN; + ret =3D poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Verify exit info. */ + ret =3D ioctl(pidfd, PIDFD_GET_INFO, &info); + ASSERT_EQ(ret, 0); + ASSERT_TRUE(info.mask & PIDFD_INFO_EXIT); + ASSERT_TRUE(WIFEXITED(info.exit_code)); + ASSERT_EQ(WEXITSTATUS(info.exit_code), 99); + + /* No zombie. */ + ret =3D waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +/* + * Test that autoreap is NOT inherited by grandchildren. + */ +TEST(autoreap_no_inherit) +{ + int ipc_sockets[2], ret; + int pidfd =3D -1; + pid_t pid; + char buf[2] =3D {}; + struct pollfd pfd; + + ret =3D socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + ASSERT_EQ(ret, 0); + + pid =3D create_autoreap_child(&pidfd); + if (pid < 0 && errno =3D=3D EINVAL) { + close(ipc_sockets[0]); + close(ipc_sockets[1]); + SKIP(return, "CLONE_AUTOREAP not supported"); + } + ASSERT_GE(pid, 0); + + if (pid =3D=3D 0) { + pid_t gc; + int status; + + close(ipc_sockets[0]); + + /* Autoreap child forks a grandchild (without autoreap). */ + gc =3D fork(); + if (gc < 0) { + write_nointr(ipc_sockets[1], "E", 1); + _exit(1); + } + if (gc =3D=3D 0) { + /* Grandchild: exit immediately. */ + close(ipc_sockets[1]); + _exit(77); + } + + /* + * The grandchild should become a regular zombie + * since it was NOT created with CLONE_AUTOREAP. + * Wait for it to verify. + */ + ret =3D waitpid(gc, &status, 0); + if (ret =3D=3D gc && WIFEXITED(status) && + WEXITSTATUS(status) =3D=3D 77) { + write_nointr(ipc_sockets[1], "P", 1); + } else { + write_nointr(ipc_sockets[1], "F", 1); + } + close(ipc_sockets[1]); + _exit(0); + } + + close(ipc_sockets[1]); + + ret =3D read_nointr(ipc_sockets[0], buf, 1); + close(ipc_sockets[0]); + ASSERT_EQ(ret, 1); + + /* + * 'P' means the autoreap child was able to waitpid() its + * grandchild (correct - grandchild should be a normal zombie, + * not autoreaped). + */ + ASSERT_EQ(buf[0], 'P'); + + /* Wait for the autoreap child to exit. */ + pfd.fd =3D pidfd; + pfd.events =3D POLLIN; + ret =3D poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + + /* Autoreap child itself should be autoreaped. */ + ret =3D waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +TEST_HARNESS_MAIN --=20 2.47.3