A divide-by-zero exception like the below could occur when IPFIX
configuration is cleared while handling sampled packets from the
datapath. While it's not valid to configure the sampling probability of
IPFIX to zero via explicitly setting it in OVSDB, it is possible to
clear the configuration, which results in a probability of zero. In this
case, there is a window during which it is possible for upcalls to find
the cleared IPFIX object and attempt to perform sampling using it. Fix
the issue by ensuring that the probability is nonzero before using it.
"Program terminated with signal SIGFPE, Arithmetic exception."
dpif_ipfix_bridge_sample (...) at ../ofproto/ofproto-dpif-ipfix.c:1701
process_upcall (...) at ../ofproto/ofproto-dpif-upcall.c:1145
recv_upcalls (...) at ../ofproto/ofproto-dpif-upcall.c:705
udpif_upcall_handler (...) at ../ofproto/ofproto-dpif-upcall.c:631
ovsthread_wrapper (...) at ../lib/ovs-thread.c:340
start_thread (...) at pthread_create.c:312
clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
Signed-off-by: Joe Stringer <joestrin...@nicira.com>
---
Given that there's a couple of other places in the IPFIX code that check
the probability before using it, I'm assuming this isn't an invariant and
this is a reasonable place to fix the bug. I haven't looked into whether
this kind of bug may affect other sampling implementations in OVS.
---
ofproto/ofproto-dpif-ipfix.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/ofproto/ofproto-dpif-ipfix.c b/ofproto/ofproto-dpif-ipfix.c
index 48ff827..9ad8fa2 100644
--- a/ofproto/ofproto-dpif-ipfix.c
+++ b/ofproto/ofproto-dpif-ipfix.c
@@ -1692,6 +1692,10 @@ dpif_ipfix_bridge_sample(struct dpif_ipfix *di, const
struct dp_packet *packet,
struct dpif_ipfix_port * tunnel_port = NULL;
ovs_mutex_lock(&mutex);
+ if (!bridge_exporter_enabled(di)) {
+ ovs_mutex_unlock(&mutex);
+ return;
+ }
/* Use the sampling probability as an approximation of the number
* of matched packets. */
packet_delta_count = UINT32_MAX / di->bridge_exporter.probability;
--
2.1.4
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