| From 5bd3c61792fe793b1d42e675b53e47396f4219a3 Mon Sep 17 00:00:00 2001 |
| From: Eric Blake <eblake@redhat.com> |
| Date: Fri, 9 Jun 2017 22:04:13 +0200 |
| Subject: [PATCH 6/6] nbd: Fix regression on resiliency to port scan |
| |
| RH-Author: Eric Blake <eblake@redhat.com> |
| Message-id: <20170609220413.28793-3-eblake@redhat.com> |
| Patchwork-id: 75575 |
| O-Subject: [RHEL-7.4 qemu-kvm PATCH 2/2] nbd: Fix regression on resiliency to port scan |
| Bugzilla: 1451614 |
| RH-Acked-by: Laszlo Ersek <lersek@redhat.com> |
| RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com> |
| RH-Acked-by: Thomas Huth <thuth@redhat.com> |
| |
| Back in qemu 2.5, qemu-nbd was immune to port probes (a transient |
| server would not quit, regardless of how many probe connections |
| came and went, until a connection actually negotiated). But we |
| broke that in commit ee7d7aa when removing the return value to |
| nbd_client_new(), although that patch also introduced a bug causing |
| an assertion failure on a client that fails negotiation. We then |
| made it worse during refactoring in commit 1a6245a (a segfault |
| before we could even assert); the (masked) assertion was cleaned |
| up in d3780c2 (still in 2.6), and just recently we finally fixed |
| the segfault ("nbd: Fully intialize client in case of failed |
| negotiation"). But that still means that ever since we added |
| TLS support to qemu-nbd, we have been vulnerable to an ill-timed |
| port-scan being able to cause a denial of service by taking down |
| qemu-nbd before a real client has a chance to connect. |
| |
| Since negotiation is now handled asynchronously via coroutines, |
| we no longer have a synchronous point of return by re-adding a |
| return value to nbd_client_new(). So this patch instead wires |
| things up to pass the negotiation status through the close_fn |
| callback function. |
| |
| Simple test across two terminals: |
| $ qemu-nbd -f raw -p 30001 file |
| $ nmap 127.0.0.1 -p 30001 && \ |
| qemu-io -c 'r 0 512' -f raw nbd://localhost:30001 |
| |
| Note that this patch does not change what constitutes successful |
| negotiation (thus, a client must enter transmission phase before |
| that client can be considered as a reason to terminate the server |
| when the connection ends). Perhaps we may want to tweak things |
| in a later patch to also treat a client that uses NBD_OPT_ABORT |
| as being a 'successful' negotiation (the client correctly talked |
| the NBD protocol, and informed us it was not going to use our |
| export after all), but that's a discussion for another day. |
| |
| Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1451614 |
| |
| Signed-off-by: Eric Blake <eblake@redhat.com> |
| Message-Id: <20170608222617.20376-1-eblake@redhat.com> |
| (cherry picked from commit ???) |
| https://bugzilla.redhat.com/show_bug.cgi?id=1451614 |
| Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com> |
| |
| Conflicts: |
| blockdev-nbd.c - context |
| include/block/nbd.h - context with nbd_client_new parameters, |
| nbd_client_close not static |
| nbd/server.c - in nbd.c instead, context, comment to nbd_client_new |
| matching different parameters |
| qemu-nbd.c - context |
| |
| blockdev-nbd.c | 7 ++++++- |
| include/block/nbd.h | 5 +++-- |
| nbd.c | 25 ++++++++++++++++--------- |
| qemu-nbd.c | 4 ++-- |
| 4 files changed, 27 insertions(+), 14 deletions(-) |
| |
| diff --git a/blockdev-nbd.c b/blockdev-nbd.c |
| index 922cf56..dc7cffa 100644 |
| |
| |
| @@ -21,6 +21,11 @@ |
| |
| static int server_fd = -1; |
| |
| +static void nbd_blockdev_client_closed(NBDClient *client, bool ignored) |
| +{ |
| + nbd_client_put(client); |
| +} |
| + |
| static void nbd_accept(void *opaque) |
| { |
| struct sockaddr_in addr; |
| @@ -28,7 +33,7 @@ static void nbd_accept(void *opaque) |
| |
| int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len); |
| if (fd >= 0) { |
| - nbd_client_new(NULL, fd, nbd_client_put); |
| + nbd_client_new(NULL, fd, nbd_blockdev_client_closed); |
| } |
| } |
| |
| diff --git a/include/block/nbd.h b/include/block/nbd.h |
| index 92e360e..963c7ce 100644 |
| |
| |
| @@ -92,8 +92,9 @@ NBDExport *nbd_export_find(const char *name); |
| void nbd_export_set_name(NBDExport *exp, const char *name); |
| void nbd_export_close_all(void); |
| |
| -void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *)); |
| -void nbd_client_close(NBDClient *client); |
| +void nbd_client_new(NBDExport *exp, int csock, |
| + void (*close_fn)(NBDClient *, bool)); |
| +void nbd_client_close(NBDClient *client, bool negotiated); |
| void nbd_client_get(NBDClient *client); |
| void nbd_client_put(NBDClient *client); |
| |
| diff --git a/nbd.c b/nbd.c |
| index b5cdc1b..c3d554d 100644 |
| |
| |
| @@ -105,7 +105,7 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports); |
| |
| struct NBDClient { |
| int refcount; |
| - void (*close)(NBDClient *client); |
| + void (*close_fn)(NBDClient *client, bool negotiated); |
| |
| NBDExport *exp; |
| int sock; |
| @@ -862,7 +862,7 @@ void nbd_client_put(NBDClient *client) |
| } |
| } |
| |
| -void nbd_client_close(NBDClient *client) |
| +void nbd_client_close(NBDClient *client, bool negotiated) |
| { |
| if (client->closing) { |
| return; |
| @@ -876,8 +876,8 @@ void nbd_client_close(NBDClient *client) |
| shutdown(client->sock, 2); |
| |
| /* Also tell the client, so that they release their reference. */ |
| - if (client->close) { |
| - client->close(client); |
| + if (client->close_fn) { |
| + client->close_fn(client, negotiated); |
| } |
| } |
| |
| @@ -964,7 +964,7 @@ void nbd_export_close(NBDExport *exp) |
| |
| nbd_export_get(exp); |
| QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) { |
| - nbd_client_close(client); |
| + nbd_client_close(client, true); |
| } |
| nbd_export_set_name(exp, NULL); |
| nbd_export_put(exp); |
| @@ -1244,7 +1244,7 @@ done: |
| |
| out: |
| nbd_request_put(req); |
| - nbd_client_close(client); |
| + nbd_client_close(client, true); |
| } |
| |
| static int nbd_can_read(void *opaque) |
| @@ -1285,7 +1285,7 @@ static coroutine_fn void nbd_co_client_start(void *opaque) |
| qemu_set_nonblock(client->sock); |
| qemu_co_mutex_init(&client->send_lock); |
| if (nbd_negotiate(data)) { |
| - nbd_client_close(client); |
| + nbd_client_close(client, false); |
| goto out; |
| } |
| qemu_set_fd_handler2(client->sock, nbd_can_read, nbd_read, NULL, client); |
| @@ -1294,7 +1294,14 @@ out: |
| g_free(data); |
| } |
| |
| -void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *)) |
| +/* |
| + * Create a new client listener on the given export @exp, using the |
| + * given socket @csock. Begin servicing it in a coroutine. When the |
| + * connection closes, call @close_fn with an indication of whether the |
| + * client completed negotiation. |
| + */ |
| +void nbd_client_new(NBDExport *exp, int csock, |
| + void (*close_fn)(NBDClient *, bool)) |
| { |
| NBDClient *client; |
| NBDClientNewData *data = g_new(NBDClientNewData, 1); |
| @@ -1303,7 +1310,7 @@ void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *)) |
| client->refcount = 1; |
| client->exp = exp; |
| client->sock = csock; |
| - client->close = close_fn; |
| + client->close_fn = close_fn; |
| |
| data->client = client; |
| data->co = qemu_coroutine_create(nbd_co_client_start); |
| diff --git a/qemu-nbd.c b/qemu-nbd.c |
| index cde7431..e0f4517 100644 |
| |
| |
| @@ -276,10 +276,10 @@ static void nbd_export_closed(NBDExport *exp) |
| state = TERMINATED; |
| } |
| |
| -static void nbd_client_closed(NBDClient *client) |
| +static void nbd_client_closed(NBDClient *client, bool negotiated) |
| { |
| nb_fds--; |
| - if (nb_fds == 0 && !persistent && state == RUNNING) { |
| + if (negotiated && nb_fds == 0 && !persistent && state == RUNNING) { |
| state = TERMINATE; |
| } |
| qemu_notify_event(); |
| -- |
| 1.8.3.1 |
| |