From f625d197050d05d33172bd5e93d044155208befb Mon Sep 17 00:00:00 2001
From: "plai@redhat.com" <plai@redhat.com>
Date: Thu, 21 Jun 2018 18:54:38 +0200
Subject: [PATCH 29/57] vhost-user: support receiving file descriptors in
 slave_read

RH-Author: plai@redhat.com
Message-id: <1529607285-9942-4-git-send-email-plai@redhat.com>
Patchwork-id: 80933
O-Subject: [RHEL7.6 PATCH BZ 1526645 03/10] vhost-user: support receiving file descriptors in slave_read
Bugzilla: 1526645
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Maxime Coquelin <maxime.coquelin@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

From: Tiwei Bie <tiwei.bie@intel.com>

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 1f3a4519b1c107b5db2434b30638353978366b4d)
Signed-off-by: Paul Lai <plai@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/virtio/vhost-user.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 38da869..85d8fd2 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -852,14 +852,44 @@ static void slave_read(void *opaque)
     VhostUserHeader hdr = { 0, };
     VhostUserPayload payload = { 0, };
     int size, ret = 0;
+    struct iovec iov;
+    struct msghdr msgh;
+    int fd = -1;
+    char control[CMSG_SPACE(sizeof(fd))];
+    struct cmsghdr *cmsg;
+    size_t fdsize;
+
+    memset(&msgh, 0, sizeof(msgh));
+    msgh.msg_iov = &iov;
+    msgh.msg_iovlen = 1;
+    msgh.msg_control = control;
+    msgh.msg_controllen = sizeof(control);
 
     /* Read header */
-    size = read(u->slave_fd, &hdr, VHOST_USER_HDR_SIZE);
+    iov.iov_base = &hdr;
+    iov.iov_len = VHOST_USER_HDR_SIZE;
+
+    size = recvmsg(u->slave_fd, &msgh, 0);
     if (size != VHOST_USER_HDR_SIZE) {
         error_report("Failed to read from slave.");
         goto err;
     }
 
+    if (msgh.msg_flags & MSG_CTRUNC) {
+        error_report("Truncated message.");
+        goto err;
+    }
+
+    for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
+         cmsg = CMSG_NXTHDR(&msgh, cmsg)) {
+            if (cmsg->cmsg_level == SOL_SOCKET &&
+                cmsg->cmsg_type == SCM_RIGHTS) {
+                    fdsize = cmsg->cmsg_len - CMSG_LEN(0);
+                    memcpy(&fd, CMSG_DATA(cmsg), fdsize);
+                    break;
+            }
+    }
+
     if (hdr.size > VHOST_USER_PAYLOAD_SIZE) {
         error_report("Failed to read msg header."
                 " Size %d exceeds the maximum %zu.", hdr.size,
@@ -883,9 +913,15 @@ static void slave_read(void *opaque)
         break;
     default:
         error_report("Received unexpected msg type.");
+        if (fd != -1) {
+            close(fd);
+        }
         ret = -EINVAL;
     }
 
+    /* Message handlers need to make sure that fd will be consumed. */
+    fd = -1;
+
     /*
      * REPLY_ACK feature handling. Other reply types has to be managed
      * directly in their request handlers.
@@ -918,6 +954,9 @@ err:
     qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);
     close(u->slave_fd);
     u->slave_fd = -1;
+    if (fd != -1) {
+        close(fd);
+    }
     return;
 }
 
-- 
1.8.3.1