97 lines
5.3 KiB
Diff
97 lines
5.3 KiB
Diff
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From 8074d64dc2eca846d6a61efe1a9b7428a0ce1dd1 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
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Date: Tue, 30 Apr 2024 11:51:15 +0100
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Subject: [PATCH] rpc: ensure temporary GSource is removed from client event
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loop
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Users are seeing periodic segfaults from libvirt client apps,
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especially thread heavy ones like virt-manager. A typical
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stack trace would end up in the virNetClientIOEventFD method,
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with illegal access to stale stack data. eg
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==238721==ERROR: AddressSanitizer: stack-use-after-return on address 0x75cd18709788 at pc 0x75cd3111f907 bp 0x75cd181ff550 sp 0x75cd181ff548
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WRITE of size 4 at 0x75cd18709788 thread T11
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#0 0x75cd3111f906 in virNetClientIOEventFD /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:1634:15
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#1 0x75cd3210d198 (/usr/lib/libglib-2.0.so.0+0x5a198) (BuildId: 0a2311dfbbc6c215dc36f4b6bdd2b4b6fbae55a2)
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#2 0x75cd3216c3be (/usr/lib/libglib-2.0.so.0+0xb93be) (BuildId: 0a2311dfbbc6c215dc36f4b6bdd2b4b6fbae55a2)
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#3 0x75cd3210ddc6 in g_main_loop_run (/usr/lib/libglib-2.0.so.0+0x5adc6) (BuildId: 0a2311dfbbc6c215dc36f4b6bdd2b4b6fbae55a2)
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#4 0x75cd3111a47c in virNetClientIOEventLoop /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:1722:9
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#5 0x75cd3111a47c in virNetClientIO /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:2002:10
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#6 0x75cd3111a47c in virNetClientSendInternal /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:2170:11
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#7 0x75cd311198a8 in virNetClientSendWithReply /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclient.c:2198:11
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#8 0x75cd31111653 in virNetClientProgramCall /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/rpc/virnetclientprogram.c:318:9
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#9 0x75cd31241c8f in callFull /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/remote/remote_driver.c:6054:10
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#10 0x75cd31241c8f in call /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/remote/remote_driver.c:6076:12
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#11 0x75cd31241c8f in remoteNetworkGetXMLDesc /usr/src/debug/libvirt/libvirt-10.2.0/build/src/remote/remote_client_bodies.h:5959:9
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#12 0x75cd31410ff7 in virNetworkGetXMLDesc /usr/src/debug/libvirt/libvirt-10.2.0/build/../src/libvirt-network.c:952:15
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The root cause is a bad assumption in the virNetClientIOEventLoop
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method. This method is run by whichever thread currently owns the
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buck, and is responsible for handling I/O. Inside a for(;;) loop,
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this method creates a temporary GSource, adds it to the event loop
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and runs g_main_loop_run(). When I/O is ready, the GSource callback
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(virNetClientIOEventFD) will fire and call g_main_loop_quit(), and
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return G_SOURCE_REMOVE which results in the temporary GSource being
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destroyed. A g_autoptr() will then remove the last reference.
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What was overlooked, is that a second thread can come along and
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while it can't enter virNetClientIOEventLoop, it will register an
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idle source that uses virNetClientIOWakeup to interrupt the
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original thread's 'g_main_loop_run' call. When this happens the
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virNetClientIOEventFD callback never runs, and so the temporary
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GSource is not destroyed. The g_autoptr() will remove a reference,
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but by virtue of still being attached to the event context, there
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is an extra reference held causing GSource to be leaked. The
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next time 'g_main_loop_run' is called, the original GSource will
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trigger its callback, and access data that was allocated on the
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stack by the previous thread, and likely SEGV.
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To solve this, the thread calling 'g_main_loop_run' must call
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g_source_destroy, immediately upon return, to guarantee that
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the temporary GSource is removed.
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CVE-2024-4418
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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Reported-by: Martin Shirokov <shirokovmartin@gmail.com>
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Tested-by: Martin Shirokov <shirokovmartin@gmail.com>
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Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
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---
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src/rpc/virnetclient.c | 14 +++++++++++++-
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1 file changed, 13 insertions(+), 1 deletion(-)
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diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c
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index 68098b1c8d8..147b0d661a3 100644
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--- a/src/rpc/virnetclient.c
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+++ b/src/rpc/virnetclient.c
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@@ -1657,7 +1657,7 @@ static int virNetClientIOEventLoop(virNetClient *client,
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#endif /* !WIN32 */
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int timeout = -1;
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virNetMessage *msg = NULL;
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- g_autoptr(GSource) G_GNUC_UNUSED source = NULL;
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+ g_autoptr(GSource) source = NULL;
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GIOCondition ev = 0;
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struct virNetClientIOEventData data = {
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.client = client,
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@@ -1721,6 +1721,18 @@ static int virNetClientIOEventLoop(virNetClient *client,
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g_main_loop_run(client->eventLoop);
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+ /*
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+ * If virNetClientIOEventFD ran, this GSource will already be
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+ * destroyed due to G_SOURCE_REMOVE. It is harmless to re-destroy
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+ * it, since we still own a reference.
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+ *
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+ * If virNetClientIOWakeup ran, it will have interrupted the
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+ * g_main_loop_run call, before virNetClientIOEventFD could
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+ * run, and thus the GSource is still registered, and we need
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+ * to destroy it since it is referencing stack memory for 'data'
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+ */
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+ g_source_destroy(source);
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+
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#ifndef WIN32
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ignore_value(pthread_sigmask(SIG_SETMASK, &oldmask, NULL));
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#endif /* !WIN32 */
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