Add a new test to ensure that when the transport changes a null pointer dereference does not occur[1].
Note that this test does not fail, but it may hang on the client side if it triggers a kernel oops. This works by creating a socket, trying to connect to a server, and then executing a second connect operation on the same socket but to a different CID (0). This triggers a transport change. If the connect operation is interrupted by a signal, this could cause a null-ptr-deref. Since this bug is non-deterministic, we need to try several times. It is safe to assume that the bug will show up within the timeout period. If there is a G2H transport loaded in the system, the bug is not triggered and this test will always pass. [1]https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/ Suggested-by: Hyunwoo Kim <v4...@theori.io> Suggested-by: Michal Luczaj <m...@rbox.co> Signed-off-by: Luigi Leonardi <leona...@redhat.com> --- This series introduces a new test that checks for a null pointer dereference that may happen when there is a transport change[1]. This bug was fixed in [2]. Note that this test *cannot* fail, it hangs if it triggers a kernel oops. The intended use-case is to run it and then check if there is any oops in the dmesg. This test is based on Hyunwoo Kim's[3] and Michal's python reproducers[4]. [1]https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/ [2]https://lore.kernel.org/netdev/20250110083511.30419-1-sgarz...@redhat.com/ [3]https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/#t [4]https://lore.kernel.org/netdev/2b3062e3-bdaa-4c94-a3c0-2930595b9...@rbox.co/ --- Changes in v2: - Addressed Stefano's comments: - Timeout is now using current_nsec() - Check for return values - Style issues - Added Hyunwoo Kim to Suggested-by - Link to v1: https://lore.kernel.org/r/20250306-test_vsock-v1-0-0320b5acc...@redhat.com --- tools/testing/vsock/Makefile | 1 + tools/testing/vsock/vsock_test.c | 101 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+) diff --git a/tools/testing/vsock/Makefile b/tools/testing/vsock/Makefile index 6e0b4e95e230500f99bb9c74350701a037ecd198..88211fd132d23ecdfd56ab0815580a237889e7f2 100644 --- a/tools/testing/vsock/Makefile +++ b/tools/testing/vsock/Makefile @@ -5,6 +5,7 @@ vsock_test: vsock_test.o vsock_test_zerocopy.o timeout.o control.o util.o msg_ze vsock_diag_test: vsock_diag_test.o timeout.o control.o util.o vsock_perf: vsock_perf.o msg_zerocopy_common.o +vsock_test: LDLIBS = -lpthread vsock_uring_test: LDLIBS = -luring vsock_uring_test: control.o util.o vsock_uring_test.o timeout.o msg_zerocopy_common.o diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c index d0f6d253ac72d08a957cb81a3c38fcc72bec5a53..d2820a67403c95bc4a7e7a16113ae2f6137b4c73 100644 --- a/tools/testing/vsock/vsock_test.c +++ b/tools/testing/vsock/vsock_test.c @@ -23,6 +23,7 @@ #include <sys/ioctl.h> #include <linux/sockios.h> #include <linux/time64.h> +#include <pthread.h> #include "vsock_test_zerocopy.h" #include "timeout.h" @@ -1788,6 +1789,101 @@ static void test_stream_connect_retry_server(const struct test_opts *opts) close(fd); } +static void *test_stream_transport_change_thread(void *vargp) +{ + pid_t *pid = (pid_t *)vargp; + + /* We want this thread to terminate as soon as possible */ + if (pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL)) { + perror("pthread_setcanceltype"); + exit(EXIT_FAILURE); + } + + while (true) { + if (kill(*pid, SIGUSR1) < 0) { + perror("kill"); + exit(EXIT_FAILURE); + } + } + return NULL; +} + +static void test_transport_change_signal_handler(int signal) +{ + /* We need a custom handler for SIGUSR1 as the default one terminates the process. */ +} + +static void test_stream_transport_change_client(const struct test_opts *opts) +{ + __sighandler_t old_handler; + pid_t pid = getpid(); + pthread_t thread_id; + time_t tout; + + old_handler = signal(SIGUSR1, test_transport_change_signal_handler); + if (old_handler == SIG_ERR) { + perror("signal"); + exit(EXIT_FAILURE); + } + + if (pthread_create(&thread_id, NULL, test_stream_transport_change_thread, &pid)) { + perror("pthread_create"); + exit(EXIT_FAILURE); + } + + tout = current_nsec() + TIMEOUT * NSEC_PER_SEC; + do { + struct sockaddr_vm sa = { + .svm_family = AF_VSOCK, + .svm_cid = opts->peer_cid, + .svm_port = opts->peer_port, + }; + int s; + + s = socket(AF_VSOCK, SOCK_STREAM, 0); + if (s < 0) { + perror("socket"); + exit(EXIT_FAILURE); + } + + connect(s, (struct sockaddr *)&sa, sizeof(sa)); + + /* Set CID to 0 cause a transport change. */ + sa.svm_cid = 0; + connect(s, (struct sockaddr *)&sa, sizeof(sa)); + + close(s); + } while (current_nsec() < tout); + + if (pthread_cancel(thread_id)) { + perror("pthread_cancel"); + exit(EXIT_FAILURE); + } + + /* Wait for the thread to terminate */ + if (pthread_join(thread_id, NULL)) { + perror("pthread_join"); + exit(EXIT_FAILURE); + } + + /* Restore the old handler */ + if (signal(SIGUSR1, old_handler) == SIG_ERR) { + perror("signal"); + exit(EXIT_FAILURE); + } +} + +static void test_stream_transport_change_server(const struct test_opts *opts) +{ + time_t tout = current_nsec() + TIMEOUT * NSEC_PER_SEC; + + do { + int s = vsock_stream_listen(VMADDR_CID_ANY, opts->peer_port); + + close(s); + } while (current_nsec() < tout); +} + static void test_stream_linger_client(const struct test_opts *opts) { struct linger optval = { @@ -1984,6 +2080,11 @@ static struct test_case test_cases[] = { .run_client = test_stream_linger_client, .run_server = test_stream_linger_server, }, + { + .name = "SOCK_STREAM transport change null-ptr-deref", + .run_client = test_stream_transport_change_client, + .run_server = test_stream_transport_change_server, + }, {}, }; --- base-commit: 4d872d51bc9d7b899c1f61534e3dbde72613f627 change-id: 20250306-test_vsock-3e77a9c7a245 Best regards, -- Luigi Leonardi <leona...@redhat.com>
