[PATCH net v2 0/3] vsock/bpf: Handle races between sockmap update and connect() disconnecting
Signal delivery during connect() may disconnect an already established socket. Problem is that such socket might have been placed in a sockmap before the connection was closed.
PATCH 1 ensures this race won't lead to an unconnected vsock staying in the sockmap. PATCH 2 selftests it.
PATCH 3 fixes a related race. Note that here the race window is rather difficult to hit and I can't think of an easy way of testing it.
Signed-off-by: Michal Luczaj mhal@rbox.co --- Changes in v2: - Handle one more path of tripping the warning - Add a selftest - Collect R-b [Stefano] - Link to v1: https://lore.kernel.org/r/20250307-vsock-trans-signal-race-v1-1-3aca3f771fbd...
--- Michal Luczaj (3): vsock/bpf: Fix EINTR connect() racing sockmap update selftest/bpf: Add test for AF_VSOCK connect() racing sockmap update vsock/bpf: Fix bpf recvmsg() racing transport reassignment
net/vmw_vsock/af_vsock.c | 10 +- net/vmw_vsock/vsock_bpf.c | 24 +++-- .../selftests/bpf/prog_tests/sockmap_basic.c | 111 +++++++++++++++++++++ 3 files changed, 136 insertions(+), 9 deletions(-) --- base-commit: da9e8efe7ee10e8425dc356a9fc593502c8e3933 change-id: 20250305-vsock-trans-signal-race-d62f7718d099
Best regards,
Signal delivery during connect() may result in a disconnect of an already TCP_ESTABLISHED socket. Problem is that such established socket might have been placed in a sockmap before the connection was closed. We end up with a SS_UNCONNECTED vsock in a sockmap. And this, combined with the ability to reassign (unconnected) vsock's transport to NULL, breaks the sockmap contract. As manifested by WARN_ON_ONCE.
connect / state = SS_CONNECTED / sock_map_update_elem if signal_pending state = SS_UNCONNECTED
connect transport = NULL vsock_bpf_recvmsg WARN_ON_ONCE(!vsk->transport)
Ensure the socket does not stay in sockmap.
WARNING: CPU: 8 PID: 1228 at net/vmw_vsock/vsock_bpf.c:97 vsock_bpf_recvmsg+0xb43/0xe00 CPU: 8 UID: 0 PID: 1228 Comm: a.out Not tainted 6.14.0-rc5+ RIP: 0010:vsock_bpf_recvmsg+0xb43/0xe00 sock_recvmsg+0x1b2/0x220 __sys_recvfrom+0x190/0x270 __x64_sys_recvfrom+0xdc/0x1b0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fixes: 634f1a7110b4 ("vsock: support sockmap") Reviewed-by: Stefano Garzarella sgarzare@redhat.com Signed-off-by: Michal Luczaj mhal@rbox.co --- net/vmw_vsock/af_vsock.c | 10 +++++++++- net/vmw_vsock/vsock_bpf.c | 1 + 2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 7e3db87ae4333cf63327ec105ca99253569bb9fe..81b1b8e9c946a646778367ab78ca180cef75ef72 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1579,7 +1579,15 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
if (signal_pending(current)) { err = sock_intr_errno(timeout); - sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE; + if (sk->sk_state == TCP_ESTABLISHED) { + /* Might have raced with a sockmap update. */ + if (sk->sk_prot->unhash) + sk->sk_prot->unhash(sk); + + sk->sk_state = TCP_CLOSING; + } else { + sk->sk_state = TCP_CLOSE; + } sock->state = SS_UNCONNECTED; vsock_transport_cancel_pkt(vsk); vsock_remove_connected(vsk); diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c index 07b96d56f3a577af71021b1b8132743554996c4f..c68fdaf09046b68254dac3ea70ffbe73dfa45cef 100644 --- a/net/vmw_vsock/vsock_bpf.c +++ b/net/vmw_vsock/vsock_bpf.c @@ -127,6 +127,7 @@ static void vsock_bpf_rebuild_protos(struct proto *prot, const struct proto *bas { *prot = *base; prot->close = sock_map_close; + prot->unhash = sock_map_unhash; prot->recvmsg = vsock_bpf_recvmsg; prot->sock_is_readable = sk_msg_is_readable; }
Racing signal-interrupted connect() and sockmap update may result in an unconnected (and missing vsock transport) socket in a sockmap.
Test spends 2 seconds attempting to reach WARN_ON_ONCE().
connect / state = SS_CONNECTED / sock_map_update_elem if signal_pending state = SS_UNCONNECTED
connect transport = NULL vsock_bpf_recvmsg WARN_ON_ONCE(!vsk->transport)
Signed-off-by: Michal Luczaj mhal@rbox.co --- .../selftests/bpf/prog_tests/sockmap_basic.c | 111 +++++++++++++++++++++ 1 file changed, 111 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c index 1e3e4392dcca0e1722c1982ecc649a80c27443b2..5c278353a924294a1452f650634cec0539804b1a 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c @@ -3,6 +3,7 @@ #include <error.h> #include <netinet/tcp.h> #include <sys/epoll.h> +#include <linux/time64.h>
#include "test_progs.h" #include "test_skmsg_load_helpers.skel.h" @@ -1042,6 +1043,114 @@ static void test_sockmap_vsock_unconnected(void) xclose(map); }
+#define CONNECT_SIGNAL_RACE_TIMEOUT 2 /* seconds */ + +static void sig_handler(int signum) +{ + /* nop */ +} + +static void connect_signal_racer_cleanup(void *map) +{ + xclose(*(int *)map); +} + +static void *connect_signal_racer(void *arg) +{ + int map; + + map = bpf_map_create(BPF_MAP_TYPE_SOCKMAP, NULL, sizeof(int), + sizeof(int), 1, NULL); + if (!ASSERT_OK_FD(map, "bpf_map_create")) + return NULL; + + pthread_cleanup_push(connect_signal_racer_cleanup, &map); + + for (;;) { + int c = *(int *)arg; + int zero = 0; + + (void)bpf_map_update_elem(map, &zero, &c, BPF_ANY); + + if (kill(0, SIGUSR1)) { + FAIL_ERRNO("kill"); + break; + } + + pthread_testcancel(); + } + + pthread_cleanup_pop(1); + + return NULL; +} + +static void test_sockmap_vsock_connect_signal_race(void) +{ + struct sockaddr_vm addr = { + .svm_family = AF_VSOCK, + .svm_cid = VMADDR_CID_LOCAL, + .svm_port = VMADDR_PORT_ANY + }; + struct sockaddr_vm bad_addr; + sighandler_t orig_handler; + pthread_t thread; + socklen_t alen; + int s, c, p; + __u64 tout; + + orig_handler = signal(SIGUSR1, sig_handler); + if (!ASSERT_NEQ(orig_handler, SIG_ERR, "signal handler setup")) + return; + + s = socket_loopback(AF_VSOCK, SOCK_SEQPACKET | SOCK_NONBLOCK); + if (s < 0) + goto restore; + + alen = sizeof(addr); + if (xgetsockname(s, (struct sockaddr *)&addr, &alen) < 0) + goto close; + + bad_addr = addr; + bad_addr.svm_cid = 0x42424242; /* non-existing */ + + if (xpthread_create(&thread, 0, connect_signal_racer, &c)) + goto close; + + tout = get_time_ns() + CONNECT_SIGNAL_RACE_TIMEOUT * NSEC_PER_SEC; + do { + c = xsocket(AF_VSOCK, SOCK_SEQPACKET, 0); + if (c < 0) + break; + + if (!connect(c, (struct sockaddr *)&addr, alen) || + errno != EINTR) + goto retry; + + if (!connect(c, (struct sockaddr *)&bad_addr, alen) || + errno != ESOCKTNOSUPPORT) + goto retry; + + if ((recv(c, &(char){0}, 1, MSG_DONTWAIT) < 0) && + errno == ENODEV) { + FAIL_ERRNO("recv"); + tout = 0; + } +retry: + xclose(c); + p = accept(s, NULL, NULL); + if (p >= 0) + xclose(p); + } while (get_time_ns() < tout); + + ASSERT_OK(pthread_cancel(thread), "pthread_cancel"); + xpthread_join(thread, NULL); +close: + xclose(s); +restore: + ASSERT_NEQ(signal(SIGUSR1, orig_handler), SIG_ERR, "handler restore"); +} + void test_sockmap_basic(void) { if (test__start_subtest("sockmap create_update_free")) @@ -1108,4 +1217,6 @@ void test_sockmap_basic(void) test_sockmap_skb_verdict_vsock_poll(); if (test__start_subtest("sockmap vsock unconnected")) test_sockmap_vsock_unconnected(); + if (test__start_subtest("sockmap vsock connect signal race")) + test_sockmap_vsock_connect_signal_race(); }
Signal delivery during connect() may lead to a disconnect of an already established socket. That involves removing socket from any sockmap and resetting state to SS_UNCONNECTED. While it correctly restores socket's proto, a call to vsock_bpf_recvmsg() might have been already under way in another thread. If the connect()ing thread reassigns the vsock transport to NULL, the recvmsg()ing thread may trigger a WARN_ON_ONCE.
connect / state = SS_CONNECTED / sock_map_update_elem vsock_bpf_recvmsg psock = sk_psock_get() lock sk if signal_pending unhash sock_map_remove_links state = SS_UNCONNECTED release sk
connect transport = NULL lock sk WARN_ON_ONCE(!vsk->transport)
Protect recvmsg() from racing against transport reassignment. Enforce the sockmap invariant that psock implies transport: lock socket before getting psock.
WARNING: CPU: 9 PID: 1222 at net/vmw_vsock/vsock_bpf.c:92 vsock_bpf_recvmsg+0xb55/0xe00 CPU: 9 UID: 0 PID: 1222 Comm: a.out Not tainted 6.14.0-rc5+ RIP: 0010:vsock_bpf_recvmsg+0xb55/0xe00 sock_recvmsg+0x1b2/0x220 __sys_recvfrom+0x190/0x270 __x64_sys_recvfrom+0xdc/0x1b0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fixes: 634f1a7110b4 ("vsock: support sockmap") Signed-off-by: Michal Luczaj mhal@rbox.co --- net/vmw_vsock/vsock_bpf.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c index c68fdaf09046b68254dac3ea70ffbe73dfa45cef..5138195d91fb258d4bc09b48e80e13651d62863a 100644 --- a/net/vmw_vsock/vsock_bpf.c +++ b/net/vmw_vsock/vsock_bpf.c @@ -73,28 +73,35 @@ static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int return err; }
-static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg, - size_t len, int flags, int *addr_len) +static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, + int flags, int *addr_len) { struct sk_psock *psock; struct vsock_sock *vsk; int copied;
+ /* Since signal delivery during connect() may reset the state of socket + * that's already in a sockmap, take the lock before checking on psock. + * This serializes a possible transport reassignment, protecting this + * function from running with NULL transport. + */ + lock_sock(sk); + psock = sk_psock_get(sk); - if (unlikely(!psock)) + if (unlikely(!psock)) { + release_sock(sk); return __vsock_recvmsg(sk, msg, len, flags); + }
- lock_sock(sk); vsk = vsock_sk(sk); - if (WARN_ON_ONCE(!vsk->transport)) { copied = -ENODEV; goto out; }
if (vsock_has_data(sk, psock) && sk_psock_queue_empty(psock)) { - release_sock(sk); sk_psock_put(sk, psock); + release_sock(sk); return __vsock_recvmsg(sk, msg, len, flags); }
@@ -108,8 +115,8 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg, }
if (sk_psock_queue_empty(psock)) { - release_sock(sk); sk_psock_put(sk, psock); + release_sock(sk); return __vsock_recvmsg(sk, msg, len, flags); }
@@ -117,8 +124,8 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg, }
out: - release_sock(sk); sk_psock_put(sk, psock); + release_sock(sk);
return copied; }
linux-kselftest-mirror@lists.linaro.org
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Michal Luczaj