[PATCH] rpc: avoid crash when system time jump back

[BiaoxiangYe <yebiaoxiang@xxxxxxxxxx>]

From: BiaoXiang Ye <yebiaoxiang@xxxxxxxxxx>

Setting the system time backward would lead to a
multiplication overflow in function virKeepAliveStart.
FunctionvirKeepAliveTimerInternal got the same bug too.

Backtrace below:
 #0  0x0000ffffae898470 in raise () from /usr/lib64/libc.so.6
 #1  0x0000ffffae89981c in abort () from /usr/lib64/libc.so.6
 #2  0x0000ffffaf9a36a8 in __mulvsi3 () from /usr/lib64/libvirt.so.0
 #3  0x0000ffffaf8fd9e8 in virKeepAliveStart (ka=0xaaaaf954ce10, interval=interval@entry=0,
     count=count@entry=0) at ../../src/rpc/virkeepalive.c:283
 #4  0x0000ffffaf908560 in virNetServerClientStartKeepAlive (client=0xaaaaf954cbe0)
     at ../../src/rpc/virnetserverclient.c:1628
 #5  0x0000aaaac57eb6dc in remoteDispatchConnectSupportsFeature (server=0xaaaaf95309d0,
     msg=0xaaaaf9549d90, ret=0xffff8c007fc0, args=0xffff8c002e70, rerr=0xffff9ea054a0,
     client=0xaaaaf954cbe0) at ../../src/remote/remote_daemon_dispatch.c:5063
 #6  remoteDispatchConnectSupportsFeatureHelper (server=0xaaaaf95309d0, client=0xaaaaf954cbe0,
     msg=0xaaaaf9549d90, rerr=0xffff9ea054a0, args=0xffff8c002e70, ret=0xffff8c007fc0)
     at ./remote/remote_daemon_dispatch_stubs.h:3503
 #7  0x0000ffffaf9053a4 in virNetServerProgramDispatchCall(msg=0xaaaaf9549d90, client=0xaaaaf954cbe0,
     server=0x0, prog=0xaaaaf953a170) at ../../src/rpc/virnetserverprogram.c:451
 #8  virNetServerProgramDispatch (prog=0xaaaaf953a170, server=0x0, server@entry=0xaaaaf95309d0,
     client=0xaaaaf954cbe0, msg=0xaaaaf9549d90) at ../../src/rpc/virnetserverprogram.c:306
 #9  0x0000ffffaf90a6bc in virNetServerProcessMsg (msg=<optimized out>, prog=<optimized out>,
     client=<optimized out>, srv=0xaaaaf95309d0) at ../../src/rpc/virnetserver.c:137
 #10 virNetServerHandleJob (jobOpaque=0xaaaaf950df80, opaque=0xaaaaf95309d0)
     at ../../src/rpc/virnetserver.c:154
 #11 0x0000ffffaf812e14 in virThreadPoolWorker (opaque=<optimized out>)
     at ../../src/util/virthreadpool.c:163
 #12 0x0000ffffaf81237c in virThreadHelper (data=<optimized out>) at ../../src/util/virthread.c:246
 #13 0x0000ffffaea327ac in ?? () from /usr/lib64/libpthread.so.0
 #14 0x0000ffffae93747c in ?? () from /usr/lib64/libc.so.6
 (gdb) frame 3
 #3  0x0000ffffaf8fd9e8 in virKeepAliveStart (ka=0xaaaaf954ce10, interval=interval@entry=0,
     count=count@entry=0) at ../../src/rpc/virkeepalive.c:283
 283	        timeout = ka->interval - delay;
 (gdb) list
 278    now = time(NULL);
 279    delay = now - ka->lastPacketReceived; <='delay' got a negative value
 280    if (delay > ka->interval)
 281        timeout = 0;
 282    else
 283        timeout = ka->interval - delay;
 284    ka->intervalStart = now - (ka->interval - timeout);
 285    ka->timer = virEventAddTimeout(timeout * 1000, virKeepAliveTimer, <= multiplication overflow
 286                                   ka, virObjectFreeCallback);
 287    if (ka->timer < 0)
 (gdb) p now
 $2 = 18288001
 (gdb) p ka->lastPacketReceived
 $3 = 1609430405

Signed-off-by: BiaoXiang Ye <yebiaoxiang@xxxxxxxxxx>
---
 src/rpc/virkeepalive.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/rpc/virkeepalive.c b/src/rpc/virkeepalive.c
index 860b91b6b1..e662484ea6 100644
--- a/src/rpc/virkeepalive.c
+++ b/src/rpc/virkeepalive.c
@@ -119,12 +119,25 @@ virKeepAliveTimerInternal(virKeepAlivePtr ka,
     if (ka->interval <= 0 || ka->intervalStart == 0)
         return false;
 
+    if (now < ka->intervalStart) {
+        VIR_WARN("system time jump back detected. now=%ld,"
+                 " intervalStart=%ld",
+                 now, ka->intervalStart);
+        ka->intervalStart = now;
+    }
+
     if (now - ka->intervalStart < ka->interval) {
         timeval = ka->interval - (now - ka->intervalStart);
         virEventUpdateTimeout(ka->timer, timeval * 1000);
         return false;
     }
 
+    if (now < ka->lastPacketReceived) {
+        VIR_WARN("system time jump back detected. now=%ld,"
+                 " lastPacketReceived=%ld",
+                 now, ka->lastPacketReceived);
+        ka->lastPacketReceived = now;
+    }
     timeval = now - ka->lastPacketReceived;
     PROBE(RPC_KEEPALIVE_TIMEOUT,
           "ka=%p client=%p countToDeath=%d idle=%d",
@@ -271,6 +284,13 @@ virKeepAliveStart(virKeepAlivePtr ka,
           ka, ka->client, interval, count);
 
     now = time(NULL);
+    if (now < ka->lastPacketReceived) {
+        VIR_WARN("system time jump back detected. now=%ld,"
+                 " lastPacketReceived=%ld",
+                 now, ka->lastPacketReceived);
+        ka->lastPacketReceived = now;
+    }
+
     delay = now - ka->lastPacketReceived;
     if (delay > ka->interval)
         timeout = 0;
-- 
2.23.0