mirror of https://github.com/torvalds/linux.git
114 lines
2.8 KiB
C
114 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define _GNU_SOURCE
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#include <errno.h>
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#include <sched.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/socket.h>
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#include <unistd.h>
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#include "../pidfd/pidfd.h"
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#include "../kselftest_harness.h"
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/*
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* Regression tests for the setns(pidfd) active reference counting bug.
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*
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* These tests are based on the reproducers that triggered the race condition
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* fixed by commit 1c465d0518dc ("ns: handle setns(pidfd, ...) cleanly").
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*
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* The bug: When using setns() with a pidfd, if the target task exits between
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* prepare_nsset() and commit_nsset(), the namespaces would become inactive.
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* Then ns_ref_active_get() would increment from 0 without properly resurrecting
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* the owner chain, causing active reference count underflows.
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*/
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/*
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* Simple pidfd setns test using create_child()+unshare().
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*
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* Without the fix, this would trigger active refcount warnings when the
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* parent exits after doing setns(pidfd) on a child that has already exited.
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*/
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TEST(simple_pidfd_setns)
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{
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pid_t child_pid;
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int pidfd = -1;
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int ret;
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int sv[2];
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char c;
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/* Ignore SIGCHLD for autoreap */
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ASSERT_NE(signal(SIGCHLD, SIG_IGN), SIG_ERR);
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ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
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/* Create a child process without namespaces initially */
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child_pid = create_child(&pidfd, 0);
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ASSERT_GE(child_pid, 0);
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if (child_pid == 0) {
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close(sv[0]);
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if (unshare(CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWNET | CLONE_NEWUSER) < 0) {
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close(sv[1]);
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_exit(1);
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}
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/* Signal parent that namespaces are ready */
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if (write_nointr(sv[1], "1", 1) < 0) {
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close(sv[1]);
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_exit(1);
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}
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close(sv[1]);
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_exit(0);
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}
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ASSERT_GE(pidfd, 0);
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EXPECT_EQ(close(sv[1]), 0);
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ret = read_nointr(sv[0], &c, 1);
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ASSERT_EQ(ret, 1);
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EXPECT_EQ(close(sv[0]), 0);
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/* Set to child's namespaces via pidfd */
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ret = setns(pidfd, CLONE_NEWUTS | CLONE_NEWIPC);
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TH_LOG("setns() returned %d", ret);
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close(pidfd);
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}
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/*
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* Simple pidfd setns test using create_child().
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*
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* This variation uses create_child() with namespace flags directly.
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* Namespaces are created immediately at clone time.
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*/
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TEST(simple_pidfd_setns_clone)
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{
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pid_t child_pid;
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int pidfd = -1;
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int ret;
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/* Ignore SIGCHLD for autoreap */
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ASSERT_NE(signal(SIGCHLD, SIG_IGN), SIG_ERR);
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/* Create a child process with new namespaces using create_child() */
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child_pid = create_child(&pidfd, CLONE_NEWUSER | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWNET);
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ASSERT_GE(child_pid, 0);
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if (child_pid == 0) {
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/* Child: sleep for a while so parent can setns to us */
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sleep(2);
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_exit(0);
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}
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/* Parent: pidfd was already created by create_child() */
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ASSERT_GE(pidfd, 0);
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/* Set to child's namespaces via pidfd */
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ret = setns(pidfd, CLONE_NEWUTS | CLONE_NEWIPC);
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close(pidfd);
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TH_LOG("setns() returned %d", ret);
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}
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TEST_HARNESS_MAIN
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