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selftests/namespaces: second inactive namespace resurrection test

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Test that socket file descriptors keep network namespaces active. Create
a network namespace, create a socket in it, then exit the namespace. The
namespace should remain active while the socket FD is held.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-56-2e6f823ebdc0@kernel.org
Tested-by: syzbot@syzkaller.appspotmail.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-10-29 13:21:09 +01:00
parent a1e49d8d18
commit c0f06da568
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1 changed files with 126 additions and 0 deletions
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126
tools/testing/selftests/namespaces/siocgskns_test.c
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@ -69,4 +69,130 @@ TEST(siocgskns_basic)
close(current_netns_fd);
}
/*
* Test that socket file descriptors keep network namespaces active.
* Create a network namespace, create a socket in it, then exit the namespace.
* The namespace should remain active while the socket FD is held.
*/
TEST(siocgskns_keeps_netns_active)
{
int sock_fd, netns_fd, test_fd;
int ipc_sockets[2];
pid_t pid;
int status;
struct stat st;
EXPECT_EQ(socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets), 0);
pid = fork();
ASSERT_GE(pid, 0);
if (pid == 0) {
/* Child: create new netns and socket */
close(ipc_sockets[0]);
if (unshare(CLONE_NEWNET) < 0) {
TH_LOG("unshare(CLONE_NEWNET) failed: %s", strerror(errno));
close(ipc_sockets[1]);
exit(1);
}
/* Create a socket in the new network namespace */
sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
if (sock_fd < 0) {
TH_LOG("socket() failed: %s", strerror(errno));
close(ipc_sockets[1]);
exit(1);
}
/* Send socket FD to parent via SCM_RIGHTS */
struct msghdr msg = {0};
struct iovec iov = {0};
char buf[1] = {'X'};
char cmsg_buf[CMSG_SPACE(sizeof(int))];
iov.iov_base = buf;
iov.iov_len = 1;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cmsg_buf;
msg.msg_controllen = sizeof(cmsg_buf);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
memcpy(CMSG_DATA(cmsg), &sock_fd, sizeof(int));
if (sendmsg(ipc_sockets[1], &msg, 0) < 0) {
close(sock_fd);
close(ipc_sockets[1]);
exit(1);
}
close(sock_fd);
close(ipc_sockets[1]);
exit(0);
}
/* Parent: receive socket FD */
close(ipc_sockets[1]);
struct msghdr msg = {0};
struct iovec iov = {0};
char buf[1];
char cmsg_buf[CMSG_SPACE(sizeof(int))];
iov.iov_base = buf;
iov.iov_len = 1;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cmsg_buf;
msg.msg_controllen = sizeof(cmsg_buf);
ssize_t n = recvmsg(ipc_sockets[0], &msg, 0);
close(ipc_sockets[0]);
ASSERT_EQ(n, 1);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
ASSERT_NE(cmsg, NULL);
ASSERT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
memcpy(&sock_fd, CMSG_DATA(cmsg), sizeof(int));
/* Wait for child to exit */
waitpid(pid, &status, 0);
ASSERT_TRUE(WIFEXITED(status));
if (WEXITSTATUS(status) != 0)
SKIP(close(sock_fd); return, "Child failed to create namespace");
/* Get network namespace from socket */
netns_fd = ioctl(sock_fd, SIOCGSKNS);
if (netns_fd < 0) {
close(sock_fd);
if (errno == ENOTTY || errno == EINVAL)
SKIP(return, "SIOCGSKNS not supported");
ASSERT_GE(netns_fd, 0);
}
ASSERT_EQ(fstat(netns_fd, &st), 0);
/*
* Namespace should still be active because socket FD keeps it alive.
* Try to access it via /proc/self/fd/<fd>.
*/
char path[64];
snprintf(path, sizeof(path), "/proc/self/fd/%d", netns_fd);
test_fd = open(path, O_RDONLY);
ASSERT_GE(test_fd, 0);
close(test_fd);
close(netns_fd);
/* Close socket - namespace should become inactive */
close(sock_fd);
/* Try SIOCGSKNS again - should fail since socket is closed */
ASSERT_LT(ioctl(sock_fd, SIOCGSKNS), 0);
}
TEST_HARNESS_MAIN