[Qemu-devel] [PATCH] vhost-user: avoid misaligned access

["Michael S. Tsirkin" <mst@redhat.com>]

We can't pass a pointer to memory field directly since
it's within a packed structure, so isn't aligned.
Pass a pointer on stack and copy.

Fixes: 30c4cc7 ("vhost: used_memslots refactoring")
Cc: Jay Zhou <jianjay.zhou@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

I had to apply this to fix make check errors with clang.
Pls review, test and ack.

Thanks!

 hw/virtio/vhost-user.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index c12fdd9..a44ee7f 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct vhost_dev *dev,
     bool reply_supported = virtio_has_feature(dev->protocol_features,
                                               VHOST_USER_PROTOCOL_F_REPLY_ACK);
     VhostUserMsg msg_reply;
+    VhostUserMemory memory = {};
     int region_i, msg_i;
 
     VhostUserMsg msg = {
@@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct vhost_dev *dev,
         msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
     }
 
-    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
+    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
         error_report("Failed preparing vhost-user memory table msg");
         return -1;
     }
+    msg.payload.memory = memory;
 
     fd_num = msg.payload.memory.nregions;
 
@@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev,
         .hdr.request = VHOST_USER_SET_MEM_TABLE,
         .hdr.flags = VHOST_USER_VERSION,
     };
+    VhostUserMemory memory = {};
 
     if (reply_supported) {
         msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
     }
 
-    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
+    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
         error_report("Failed preparing vhost-user memory table msg");
         return -1;
     }
 
+    msg.payload.memory = memory;
+
     fd_num = msg.payload.memory.nregions;
 
     if (!fd_num) {
@@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct vhost_dev *dev)
 {
     int fds[VHOST_MEMORY_MAX_NREGIONS];
     VhostUserMsg msg;
+    VhostUserMemory memory = {};
+
+    vhost_user_prepare_msg(dev, &memory, fds);
 
-    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
+    msg.payload.memory = memory;
 }
 
 const VhostOps user_ops = {
-- 
MST