qemu-kvm/SOURCES/kvm-nbd-server-Plumb-in-new-args-to-nbd_client_add.patch

From 0d204cb81aec2b13254a0bd53938f53bfea81cb5 Mon Sep 17 00:00:00 2001
From: Eric Blake <eblake@redhat.com>
Date: Wed, 7 Aug 2024 08:50:01 -0500
Subject: [PATCH 1/5] nbd/server: Plumb in new args to nbd_client_add()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

RH-Author: Eric Blake <eblake@redhat.com>
RH-MergeRequest: 388: nbd/server: fix CVE-2024-7409 (qemu crash on nbd-server-stop) [rhel-8.10.z]
RH-Jira: RHEL-52611
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Richard W.M. Jones <rjones@redhat.com>
RH-Commit: [1/4] 292be8dd2df2a840b2200e31a27e9d17fdab91ad (ebblake/qemu-kvm)

Upcoming patches to fix a CVE need to track an opaque pointer passed
in by the owner of a client object, as well as request for a time
limit on how fast negotiation must complete.  Prepare for that by
changing the signature of nbd_client_new() and adding an accessor to
get at the opaque pointer, although for now the two servers
(qemu-nbd.c and blockdev-nbd.c) do not change behavior even though
they pass in a new default timeout value.

Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240807174943.771624-11-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
[eblake: s/LIMIT/MAX_SECS/ as suggested by Dan]
Signed-off-by: Eric Blake <eblake@redhat.com>

(cherry picked from commit fb1c2aaa981e0a2fa6362c9985f1296b74f055ac)
Jira: https://issues.redhat.com/browse/RHEL-52611
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 blockdev-nbd.c      |  6 ++++--
 include/block/nbd.h | 11 ++++++++++-
 nbd/server.c        | 20 +++++++++++++++++---
 qemu-nbd.c          |  4 +++-
 4 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index bdfa7ed3a5..b9e8dc78f3 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -59,8 +59,10 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
     nbd_update_server_watch(nbd_server);
 
     qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
-    nbd_client_new(cioc, nbd_server->tlscreds, nbd_server->tlsauthz,
-                   nbd_blockdev_client_closed);
+    /* TODO - expose handshake timeout as QMP option */
+    nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS,
+                   nbd_server->tlscreds, nbd_server->tlsauthz,
+                   nbd_blockdev_client_closed, NULL);
 }
 
 static void nbd_update_server_watch(NBDServerData *s)
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 78d101b774..b71a297249 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -27,6 +27,12 @@
 
 extern const BlockExportDriver blk_exp_nbd;
 
+/*
+ * NBD_DEFAULT_HANDSHAKE_MAX_SECS: Number of seconds in which client must
+ * succeed at NBD_OPT_GO before being forcefully dropped as too slow.
+ */
+#define NBD_DEFAULT_HANDSHAKE_MAX_SECS 10
+
 /* Handshake phase structs - this struct is passed on the wire */
 
 struct NBDOption {
@@ -338,9 +344,12 @@ AioContext *nbd_export_aio_context(NBDExport *exp);
 NBDExport *nbd_export_find(const char *name);
 
 void nbd_client_new(QIOChannelSocket *sioc,
+                    uint32_t handshake_max_secs,
                     QCryptoTLSCreds *tlscreds,
                     const char *tlsauthz,
-                    void (*close_fn)(NBDClient *, bool));
+                    void (*close_fn)(NBDClient *, bool),
+                    void *owner);
+void *nbd_client_owner(NBDClient *client);
 void nbd_client_get(NBDClient *client);
 void nbd_client_put(NBDClient *client);
 
diff --git a/nbd/server.c b/nbd/server.c
index 6db124cf53..cc1b6838bf 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -120,10 +120,12 @@ typedef struct NBDExportMetaContexts {
 struct NBDClient {
     int refcount;
     void (*close_fn)(NBDClient *client, bool negotiated);
+    void *owner;
 
     NBDExport *exp;
     QCryptoTLSCreds *tlscreds;
     char *tlsauthz;
+    uint32_t handshake_max_secs;
     QIOChannelSocket *sioc; /* The underlying data channel */
     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
 
@@ -2706,6 +2708,7 @@ static coroutine_fn void nbd_co_client_start(void *opaque)
 
     qemu_co_mutex_init(&client->send_lock);
 
+    /* TODO - utilize client->handshake_max_secs */
     if (nbd_negotiate(client, &local_err)) {
         if (local_err) {
             error_report_err(local_err);
@@ -2718,14 +2721,17 @@ static coroutine_fn void nbd_co_client_start(void *opaque)
 }
 
 /*
- * Create a new client listener using the given channel @sioc.
+ * Create a new client listener using the given channel @sioc and @owner.
  * Begin servicing it in a coroutine.  When the connection closes, call
- * @close_fn with an indication of whether the client completed negotiation.
+ * @close_fn with an indication of whether the client completed negotiation
+ * within @handshake_max_secs seconds (0 for unbounded).
  */
 void nbd_client_new(QIOChannelSocket *sioc,
+                    uint32_t handshake_max_secs,
                     QCryptoTLSCreds *tlscreds,
                     const char *tlsauthz,
-                    void (*close_fn)(NBDClient *, bool))
+                    void (*close_fn)(NBDClient *, bool),
+                    void *owner)
 {
     NBDClient *client;
     Coroutine *co;
@@ -2737,13 +2743,21 @@ void nbd_client_new(QIOChannelSocket *sioc,
         object_ref(OBJECT(client->tlscreds));
     }
     client->tlsauthz = g_strdup(tlsauthz);
+    client->handshake_max_secs = handshake_max_secs;
     client->sioc = sioc;
     qio_channel_set_delay(QIO_CHANNEL(sioc), false);
     object_ref(OBJECT(client->sioc));
     client->ioc = QIO_CHANNEL(sioc);
     object_ref(OBJECT(client->ioc));
     client->close_fn = close_fn;
+    client->owner = owner;
 
     co = qemu_coroutine_create(nbd_co_client_start, client);
     qemu_coroutine_enter(co);
 }
+
+void *
+nbd_client_owner(NBDClient *client)
+{
+    return client->owner;
+}
diff --git a/qemu-nbd.c b/qemu-nbd.c
index c6c20df68a..f48abf379e 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -363,7 +363,9 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
 
     nb_fds++;
     nbd_update_server_watch();
-    nbd_client_new(cioc, tlscreds, tlsauthz, nbd_client_closed);
+    /* TODO - expose handshake timeout as command line option */
+    nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS,
+                   tlscreds, tlsauthz, nbd_client_closed, NULL);
 }
 
 static void nbd_update_server_watch(void)
-- 
2.39.3