patches: Add backport/rpc-ensure-temporary-GSource-is-removed-from-client-event.patch

CVE-2024-4418

Closes: #1070330

debian/patches/backport/rpc-ensure-temporary-GSource-is-removed-from-client-event.patch

+From: =?utf-8?b?IkRhbmllbCBQLiBCZXJyYW5nw6ki?= <berrange@redhat.com>
+Date: Tue, 30 Apr 2024 11:51:15 +0100
+Subject: rpc: ensure temporary GSource is removed from client event loop
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+Users are seeing periodic segfaults from libvirt client apps,
+especially thread heavy ones like virt-manager. A typical
+stack trace would end up in the virNetClientIOEventFD method,
+with illegal access to stale stack data. eg
+
+==238721==ERROR: AddressSanitizer: stack-use-after-return on address 0x75cd18709788 at pc 0x75cd3111f907 bp 0x75cd181ff550 sp 0x75cd181ff548
+WRITE of size 4 at 0x75cd18709788 thread T11
+    #0 0x75cd3111f906 in virNetClientIOEventFD /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:1634:15
+    #1 0x75cd3210d198  (/usr/lib/libglib-2.0.so.0+0x5a198) (BuildId: 0a2311dfbbc6c215dc36f4b6bdd2b4b6fbae55a2)
+    #2 0x75cd3216c3be  (/usr/lib/libglib-2.0.so.0+0xb93be) (BuildId: 0a2311dfbbc6c215dc36f4b6bdd2b4b6fbae55a2)
+    #3 0x75cd3210ddc6 in g_main_loop_run (/usr/lib/libglib-2.0.so.0+0x5adc6) (BuildId: 0a2311dfbbc6c215dc36f4b6bdd2b4b6fbae55a2)
+    #4 0x75cd3111a47c in virNetClientIOEventLoop /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:1722:9
+    #5 0x75cd3111a47c in virNetClientIO /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:2002:10
+    #6 0x75cd3111a47c in virNetClientSendInternal /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:2170:11
+    #7 0x75cd311198a8 in virNetClientSendWithReply /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:2198:11
+    #8 0x75cd31111653 in virNetClientProgramCall /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclientprogram.c:318:9
+    #9 0x75cd31241c8f in callFull /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/remote/remote_driver.c:6054:10
+    #10 0x75cd31241c8f in call /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/remote/remote_driver.c:6076:12
+    #11 0x75cd31241c8f in remoteNetworkGetXMLDesc /usr/src/debug/libvirt/libvirt-10.2.0/build/src/remote/remote_client_bodies.h:5959:9
+    #12 0x75cd31410ff7 in virNetworkGetXMLDesc /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/libvirt-network.c:952:15
+
+The root cause is a bad assumption in the virNetClientIOEventLoop
+method. This method is run by whichever thread currently owns the
+buck, and is responsible for handling I/O. Inside a for(;;) loop,
+this method creates a temporary GSource, adds it to the event loop
+and runs g_main_loop_run(). When I/O is ready, the GSource callback
+(virNetClientIOEventFD) will fire and call g_main_loop_quit(), and
+return G_SOURCE_REMOVE which results in the temporary GSource being
+destroyed. A g_autoptr() will then remove the last reference.
+
+What was overlooked, is that a second thread can come along and
+while it can't enter virNetClientIOEventLoop, it will register an
+idle source that uses virNetClientIOWakeup to interrupt the
+original thread's 'g_main_loop_run' call. When this happens the
+virNetClientIOEventFD callback never runs, and so the temporary
+GSource is not destroyed. The g_autoptr() will remove a reference,
+but by virtue of still being attached to the event context, there
+is an extra reference held causing GSource to be leaked. The
+next time 'g_main_loop_run' is called, the original GSource will
+trigger its callback, and access data that was allocated on the
+stack by the previous thread, and likely SEGV.
+
+To solve this, the thread calling 'g_main_loop_run' must call
+g_source_destroy, immediately upon return, to guarantee that
+the temporary GSource is removed.
+
+CVE-2024-4418
+Reviewed-by: Ján Tomko <jtomko@redhat.com>
+Reported-by: Martin Shirokov <shirokovmartin@gmail.com>
+Tested-by: Martin Shirokov <shirokovmartin@gmail.com>
+Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
+(cherry picked from commit 8074d64dc2eca846d6a61efe1a9b7428a0ce1dd1)
+
+Forwarded: not-needed
+Origin: https://gitlab.com/libvirt/libvirt/-/commit/8074d64dc2eca846d6a61efe1a9b7428a0ce1dd1
+---
+ src/rpc/virnetclient.c | 14 +++++++++++++-
+ 1 file changed, 13 insertions(+), 1 deletion(-)
+
+diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c
+index 68098b1..147b0d6 100644
+--- a/src/rpc/virnetclient.c
++++ b/src/rpc/virnetclient.c
+@@ -1657,7 +1657,7 @@ static int virNetClientIOEventLoop(virNetClient *client,
+ #endif /* !WIN32 */
+         int timeout = -1;
+         virNetMessage *msg = NULL;
+-        g_autoptr(GSource) G_GNUC_UNUSED source = NULL;
++        g_autoptr(GSource) source = NULL;
+         GIOCondition ev = 0;
+         struct virNetClientIOEventData data = {
+             .client = client,
+@@ -1721,6 +1721,18 @@ static int virNetClientIOEventLoop(virNetClient *client,
+ 
+         g_main_loop_run(client->eventLoop);
+ 
++        /*
++         * If virNetClientIOEventFD ran, this GSource will already be
++         * destroyed due to G_SOURCE_REMOVE. It is harmless to re-destroy
++         * it, since we still own a reference.
++         *
++         * If virNetClientIOWakeup ran, it will have interrupted the
++         * g_main_loop_run call, before virNetClientIOEventFD could
++         * run, and thus the GSource is still registered, and we need
++         * to destroy it since it is referencing stack memory for 'data'
++         */
++        g_source_destroy(source);
++
+ #ifndef WIN32
+         ignore_value(pthread_sigmask(SIG_SETMASK, &oldmask, NULL));
+ #endif /* !WIN32 */

debian/patches/series

+backport/rpc-ensure-temporary-GSource-is-removed-from-client-event.patch
 forward/Reduce-udevadm-settle-timeout-to-10-seconds.patch
 debian/Debianize-libvirt-guests.patch
 debian/apparmor_profiles_local_include.patch