[dpdk-stable] patch 'vhost: fix crash' has been queued to LTS release 17.11.1

[Yuanhan Liu]

Hi,

FYI, your patch has been queued to LTS release 17.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 01/26/18. So please
shout if anyone has objections.

Thanks.

	--yliu

---
>From e1fd3c6f9e695da2e74a939bba129b92a0d09d95 Mon Sep 17 00:00:00 2001
From: Jianfeng Tan <jianfeng.tan at intel.com>
Date: Wed, 15 Nov 2017 11:41:08 +0000
Subject: [PATCH] vhost: fix crash

[ upstream commit cab278dee9290ee48062576b09d21e6c1eb0214b ]

In a running VM, operations (like device attach/detach) will
trigger the QEMU to resend set_mem_table to vhost-user backend.

DPDK vhost-user handles this message rudely by unmap all existing
regions and map new ones. This might lead to segfault if there
is pmd thread just trying to touch those unmapped memory regions.

But for most cases, except VM memory hotplug, QEMU still sends the
set_mem_table message even the memory regions are not changed as
QEMU vhost-user filters out those not backed by file (fd > 0).

To fix this case, we add a check in the handler to see if the
memory regions are really changed; if not, we just keep old memory
regions.

Fixes: 8f972312b8f4 ("vhost: support vhost-user")

Reported-by: Yang Zhang <zy107165 at alibaba-inc.com>
Reported-by: Xin Long <longxin.xl at alibaba-inc.com>
Signed-off-by: Yi Yang <yi.y.yang at intel.com>
Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
Acked-by: Yuanhan Liu <yliu at fridaylinux.org>
---
 lib/librte_vhost/vhost_user.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index f4c7ce4..6f3869c 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -573,6 +573,30 @@ dump_guest_pages(struct virtio_net *dev)
 #define dump_guest_pages(dev)
 #endif
 
+static bool
+vhost_memory_changed(struct VhostUserMemory *new,
+		     struct rte_vhost_memory *old)
+{
+	uint32_t i;
+
+	if (new->nregions != old->nregions)
+		return true;
+
+	for (i = 0; i < new->nregions; ++i) {
+		VhostUserMemoryRegion *new_r = &new->regions[i];
+		struct rte_vhost_mem_region *old_r = &old->regions[i];
+
+		if (new_r->guest_phys_addr != old_r->guest_phys_addr)
+			return true;
+		if (new_r->memory_size != old_r->size)
+			return true;
+		if (new_r->userspace_addr != old_r->guest_user_addr)
+			return true;
+	}
+
+	return false;
+}
+
 static int
 vhost_user_set_mem_table(struct virtio_net *dev, struct VhostUserMsg *pmsg)
 {
@@ -585,6 +609,16 @@ vhost_user_set_mem_table(struct virtio_net *dev, struct VhostUserMsg *pmsg)
 	uint32_t i;
 	int fd;
 
+	if (dev->mem && !vhost_memory_changed(&memory, dev->mem)) {
+		RTE_LOG(INFO, VHOST_CONFIG,
+			"(%d) memory regions not changed\n", dev->vid);
+
+		for (i = 0; i < memory.nregions; i++)
+			close(pmsg->fds[i]);
+
+		return 0;
+	}
+
 	if (dev->mem) {
 		free_mem_region(dev);
 		rte_free(dev->mem);
-- 
2.7.4