From a0823c276671b0253f77cf5a1550995c3d06050f Mon Sep 17 00:00:00 2001 From: Zhu Yangyang Date: Mon, 8 Apr 2024 11:00:43 -0500 Subject: [PATCH] nbd/server: do not poll within a coroutine context 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 (cherry picked from commit ae6d91a7e9b77abb029ed3fa9fad461422286942) Signed-off-by: Michael Tokarev --- 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 30d5383cb19..15503d09288 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 ddfe7d11837..c201b58a838 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 1b2141ab4b2..c18554cb873 100644 --- a/nbd/nbd-internal.h +++ b/nbd/nbd-internal.h @@ -71,16 +71,6 @@ 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 ada16089f32..4d2061f55c6 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -729,6 +729,23 @@ 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. */ @@ -737,7 +754,7 @@ 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); @@ -758,17 +775,18 @@ 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); -- 2.39.5