selftests/namespaces: Fix waitpid race in listns_efault_test cleanup

The efault tests spawn two categories of child processes: namespace
children (each in its own mount namespace, for concurrent destruction) and
an iterator child that calls listns() in a tight loop.  The cleanup loop
used waitpid(-1), which reaps any child in any order. If the iterator child
exits early (e.g. because listns() returned ENOSYS) before all namespace
children have been reaped, waitpid(-1) may consume it instead.  The
subsequent targeted waitpid(iter_pid) would then block indefinitely.

Track the PIDs of the namespace children explicitly and use targeted
waitpid() calls in the cleanup loop so the iterator child cannot be
inadvertently reaped during namespace cleanup.

Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://patch.msgid.link/20260407-selftests-namespaces_fixes-v1-2-59109909d88b@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/namespaces/listns_efault_test.c b/tools/testing/selftests/namespaces/listns_efault_test.c
index b570746e917c117a2ccb19044334195bfe802dfa..8df5397adbb0da902077dd330551b71b5772336a 100644 (file)
--- a/tools/testing/selftests/namespaces/listns_efault_test.c
+++ b/tools/testing/selftests/namespaces/listns_efault_test.c
@@ -38,7 +38,7 @@ TEST(listns_partial_fault_with_ns_cleanup)
        __u64 *ns_ids;
        ssize_t ret;
        long page_size;
-       pid_t pid, iter_pid;
+       pid_t pid, iter_pid, ns_pids[5];
        int pidfds[5];
        int sv[5][2];
        int iter_pidfd;
@@ -114,6 +114,7 @@ TEST(listns_partial_fault_with_ns_cleanup)
 
                pid = create_child(&pidfds[i], CLONE_NEWNS);
                ASSERT_NE(pid, -1);
+               ns_pids[i] = pid;
 
                if (pid == 0) {
                        close(sv[i][0]); /* Close parent end */
@@ -164,7 +165,7 @@ TEST(listns_partial_fault_with_ns_cleanup)
 
        /* Wait for all mount namespace children to exit and cleanup */
        for (i = 0; i < 5; i++) {
-               waitpid(-1, NULL, 0);
+               waitpid(ns_pids[i], NULL, 0);
                close(sv[i][0]);
                close(pidfds[i]);
        }
@@ -250,7 +251,7 @@ TEST(listns_late_fault_with_ns_cleanup)
        __u64 *ns_ids;
        ssize_t ret;
        long page_size;
-       pid_t pid, iter_pid;
+       pid_t pid, iter_pid, ns_pids[10];
        int pidfds[10];
        int sv[10][2];
        int iter_pidfd;
@@ -320,6 +321,7 @@ TEST(listns_late_fault_with_ns_cleanup)
 
                pid = create_child(&pidfds[i], CLONE_NEWNS);
                ASSERT_NE(pid, -1);
+               ns_pids[i] = pid;
 
                if (pid == 0) {
                        close(sv[i][0]); /* Close parent end */
@@ -373,7 +375,7 @@ TEST(listns_late_fault_with_ns_cleanup)
 
        /* Wait for all children and cleanup */
        for (i = 0; i < 10; i++) {
-               waitpid(-1, NULL, 0);
+               waitpid(ns_pids[i], NULL, 0);
                close(sv[i][0]);
                close(pidfds[i]);
        }
@@ -402,7 +404,7 @@ TEST(listns_mnt_ns_cleanup_on_fault)
        __u64 *ns_ids;
        ssize_t ret;
        long page_size;
-       pid_t pid, iter_pid;
+       pid_t pid, iter_pid, ns_pids[8];
        int pidfds[8];
        int sv[8][2];
        int iter_pidfd;
@@ -462,6 +464,7 @@ TEST(listns_mnt_ns_cleanup_on_fault)
 
                pid = create_child(&pidfds[i], CLONE_NEWNS);
                ASSERT_NE(pid, -1);
+               ns_pids[i] = pid;
 
                if (pid == 0) {
                        close(sv[i][0]); /* Close parent end */
@@ -508,7 +511,7 @@ TEST(listns_mnt_ns_cleanup_on_fault)
 
        /* Wait for children and cleanup */
        for (i = 0; i < 8; i++) {
-               waitpid(-1, NULL, 0);
+               waitpid(ns_pids[i], NULL, 0);
                close(sv[i][0]);
                close(pidfds[i]);
        }