From ae9ebfc4ebd6f146951f04cf9e12eeaaf4c2387e Mon Sep 17 00:00:00 2001 From: Zhu Yangyang Date: Mon, 8 Apr 2024 11:00:43 -0500 Subject: [PATCH 1/2] nbd/server: do not poll within a coroutine context RH-Author: Eric Blake RH-MergeRequest: 239: avoid destination hang on NBD+TLS storage migration RH-Jira: RHEL-33440 RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Miroslav Rezanina RH-Commit: [1/2] 27963e92aacca8ed43994113b645f472fba8f8bc (ebblake/centos-qemu-kvm) Coroutines are not supposed to block. Instead, they should yield. The client performs TLS upgrade outside of an AIOContext, during synchronous handshake; this still requires g_main_loop. But the server responds to TLS upgrade inside a coroutine, so a nested g_main_loop is wrong. Since the two callbacks no longer share more than the setting of data.complete and data.error, it's just as easy to use static helpers instead of trying to share a common code path. It is also possible to add assertions that no other code is interfering with the eventual path to qio reaching the callback, whether or not it required a yield or main loop. Fixes: f95910f ("nbd: implement TLS support in the protocol negotiation") Signed-off-by: Zhu Yangyang [eblake: move callbacks to their use point, add assertions] Signed-off-by: Eric Blake Message-ID: <20240408160214.1200629-5-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy Jira: https://issues.redhat.com/browse/RHEL-33440 (cherry picked from commit ae6d91a7e9b77abb029ed3fa9fad461422286942) Signed-off-by: Eric Blake --- nbd/client.c | 28 ++++++++++++++++++++++++---- nbd/common.c | 11 ----------- nbd/nbd-internal.h | 10 ---------- nbd/server.c | 28 +++++++++++++++++++++++----- 4 files changed, 47 insertions(+), 30 deletions(-) diff --git a/nbd/client.c b/nbd/client.c index 29ffc609a4..c89c750467 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -596,13 +596,31 @@ static int nbd_request_simple_option(QIOChannel *ioc, int opt, bool strict, return 1; } +/* Callback to learn when QIO TLS upgrade is complete */ +struct NBDTLSClientHandshakeData { + bool complete; + Error *error; + GMainLoop *loop; +}; + +static void nbd_client_tls_handshake(QIOTask *task, void *opaque) +{ + struct NBDTLSClientHandshakeData *data = opaque; + + qio_task_propagate_error(task, &data->error); + data->complete = true; + if (data->loop) { + g_main_loop_quit(data->loop); + } +} + static QIOChannel *nbd_receive_starttls(QIOChannel *ioc, QCryptoTLSCreds *tlscreds, const char *hostname, Error **errp) { int ret; QIOChannelTLS *tioc; - struct NBDTLSHandshakeData data = { 0 }; + struct NBDTLSClientHandshakeData data = { 0 }; ret = nbd_request_simple_option(ioc, NBD_OPT_STARTTLS, true, errp); if (ret <= 0) { @@ -619,18 +637,20 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc, return NULL; } qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls"); - data.loop = g_main_loop_new(g_main_context_default(), FALSE); trace_nbd_receive_starttls_tls_handshake(); qio_channel_tls_handshake(tioc, - nbd_tls_handshake, + nbd_client_tls_handshake, &data, NULL, NULL); if (!data.complete) { + data.loop = g_main_loop_new(g_main_context_default(), FALSE); g_main_loop_run(data.loop); + assert(data.complete); + g_main_loop_unref(data.loop); } - g_main_loop_unref(data.loop); + if (data.error) { error_propagate(errp, data.error); object_unref(OBJECT(tioc)); diff --git a/nbd/common.c b/nbd/common.c index 3247c1d618..589a748cfe 100644 --- a/nbd/common.c +++ b/nbd/common.c @@ -47,17 +47,6 @@ int nbd_drop(QIOChannel *ioc, size_t size, Error **errp) } -void nbd_tls_handshake(QIOTask *task, - void *opaque) -{ - struct NBDTLSHandshakeData *data = opaque; - - qio_task_propagate_error(task, &data->error); - data->complete = true; - g_main_loop_quit(data->loop); -} - - const char *nbd_opt_lookup(uint32_t opt) { switch (opt) { diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h index dfa02f77ee..91895106a9 100644 --- a/nbd/nbd-internal.h +++ b/nbd/nbd-internal.h @@ -72,16 +72,6 @@ static inline int nbd_write(QIOChannel *ioc, const void *buffer, size_t size, return qio_channel_write_all(ioc, buffer, size, errp) < 0 ? -EIO : 0; } -struct NBDTLSHandshakeData { - GMainLoop *loop; - bool complete; - Error *error; -}; - - -void nbd_tls_handshake(QIOTask *task, - void *opaque); - int nbd_drop(QIOChannel *ioc, size_t size, Error **errp); #endif diff --git a/nbd/server.c b/nbd/server.c index c3484cc1eb..98ae0e1632 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -748,6 +748,23 @@ static int nbd_negotiate_handle_info(NBDClient *client, Error **errp) return rc; } +/* Callback to learn when QIO TLS upgrade is complete */ +struct NBDTLSServerHandshakeData { + bool complete; + Error *error; + Coroutine *co; +}; + +static void nbd_server_tls_handshake(QIOTask *task, void *opaque) +{ + struct NBDTLSServerHandshakeData *data = opaque; + + qio_task_propagate_error(task, &data->error); + data->complete = true; + if (!qemu_coroutine_entered(data->co)) { + aio_co_wake(data->co); + } +} /* Handle NBD_OPT_STARTTLS. Return NULL to drop connection, or else the * new channel for all further (now-encrypted) communication. */ @@ -756,7 +773,7 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, { QIOChannel *ioc; QIOChannelTLS *tioc; - struct NBDTLSHandshakeData data = { 0 }; + struct NBDTLSServerHandshakeData data = { 0 }; assert(client->opt == NBD_OPT_STARTTLS); @@ -777,17 +794,18 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-server-tls"); trace_nbd_negotiate_handle_starttls_handshake(); - data.loop = g_main_loop_new(g_main_context_default(), FALSE); + data.co = qemu_coroutine_self(); qio_channel_tls_handshake(tioc, - nbd_tls_handshake, + nbd_server_tls_handshake, &data, NULL, NULL); if (!data.complete) { - g_main_loop_run(data.loop); + qemu_coroutine_yield(); + assert(data.complete); } - g_main_loop_unref(data.loop); + if (data.error) { object_unref(OBJECT(tioc)); error_propagate(errp, data.error); -- 2.39.3