[PATCH v5 48/50] multi-process: Validate incoming commands from Proxy

[Jagannathan Raman]

From: Elena Ufimtseva <address@hidden>

Validate the incoming commands to confirm that they would not cause any
errors in the remote process.

Signed-off-by: Elena Ufimtseva <address@hidden>
Signed-off-by: Jagannathan Raman <address@hidden>
Signed-off-by: John G Johnson <address@hidden>
---
 hw/proxy/qemu-proxy.c    |  6 +++-
 include/io/mpqemu-link.h |  2 ++
 io/mpqemu-link.c         | 75 +++++++++++++++++++++++++++++++++++++++++++++++-
 remote/remote-main.c     |  4 +++
 4 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/hw/proxy/qemu-proxy.c b/hw/proxy/qemu-proxy.c
index 4d4eff4..7330094 100644
--- a/hw/proxy/qemu-proxy.c
+++ b/hw/proxy/qemu-proxy.c
@@ -868,7 +868,11 @@ static void send_bar_access_msg(PCIProxyDev *dev, 
MemoryRegion *mr,
 
     mpqemu_msg_recv(&ret, mpqemu_link->mmio);
 
-    *val = ret.data1.mmio_ret.val;
+    if (!mpqemu_msg_valid(&ret)) {
+        *val = 0;
+    } else {
+        *val = ret.data1.mmio_ret.val;
+    }
 }
 
 void proxy_default_bar_write(void *opaque, hwaddr addr, uint64_t val,
diff --git a/include/io/mpqemu-link.h b/include/io/mpqemu-link.h
index 722f08c..2f44f31 100644
--- a/include/io/mpqemu-link.h
+++ b/include/io/mpqemu-link.h
@@ -213,4 +213,6 @@ void mpqemu_start_coms(MPQemuLinkState *s);
 uint64_t wait_for_remote(int efd);
 void notify_proxy(int fd, uint64_t val);
 
+bool mpqemu_msg_valid(MPQemuMsg *msg);
+
 #endif
diff --git a/io/mpqemu-link.c b/io/mpqemu-link.c
index 07a9be9..298bb58 100644
--- a/io/mpqemu-link.c
+++ b/io/mpqemu-link.c
@@ -65,7 +65,7 @@ void mpqemu_link_finalize(MPQemuLinkState *s)
 void mpqemu_msg_send(MPQemuMsg *msg, MPQemuChannel *chan)
 {
     int rc;
-    uint8_t *data;
+    uint8_t *data = NULL;
     union {
         char control[CMSG_SPACE(REMOTE_MAX_FDS * sizeof(int))];
         struct cmsghdr align;
@@ -335,3 +335,76 @@ void mpqemu_start_coms(MPQemuLinkState *s)
 
     g_main_loop_run(s->loop);
 }
+
+bool mpqemu_msg_valid(MPQemuMsg *msg)
+{
+    if (msg->cmd >= MAX) {
+        return false;
+    }
+
+    if (msg->bytestream) {
+        if (!msg->data2) {
+            return false;
+        }
+    } else {
+        if (msg->data2) {
+            return false;
+        }
+    }
+
+    /* Verify FDs. */
+    if (msg->num_fds >= REMOTE_MAX_FDS) {
+        return false;
+    }
+    if (msg->num_fds > 0) {
+        for (int i = 0; i < msg->num_fds; i++) {
+            if (fcntl(msg->fds[i], F_GETFL) == -1) {
+                return false;
+            }
+        }
+    }
+
+    /* Verify ID size. */
+    if (msg->id >= UINT64_MAX) {
+        return false;
+    }
+
+    /* Verify message specific fields. */
+    switch (msg->cmd) {
+    case SYNC_SYSMEM:
+        if (msg->num_fds == 0 || msg->bytestream != 0) {
+            return false;
+        }
+        if (msg->size != sizeof(msg->data1)) {
+            return false;
+        }
+        break;
+    case PCI_CONFIG_WRITE:
+    case PCI_CONFIG_READ:
+        if (msg->size != sizeof(struct conf_data_msg)) {
+            return false;
+        }
+        break;
+    case BAR_WRITE:
+    case BAR_READ:
+    case SET_IRQFD:
+    case MMIO_RETURN:
+    case DEVICE_RESET:
+    case RUNSTATE_SET:
+        if (msg->size != sizeof(msg->data1)) {
+            return false;
+        }
+        break;
+    case PROXY_PING:
+    case START_MIG_OUT:
+    case START_MIG_IN:
+        if (msg->size != 0) {
+            return false;
+        }
+        break;
+    default:
+        break;
+    }
+
+    return true;
+}
diff --git a/remote/remote-main.c b/remote/remote-main.c
index 20d160e..c4aa3e0 100644
--- a/remote/remote-main.c
+++ b/remote/remote-main.c
@@ -435,6 +435,10 @@ static void process_msg(GIOCondition cond, MPQemuChannel 
*chan)
     if (msg->id > MAX_REMOTE_DEVICES) {
         error_setg(&err, "id of the device is larger than max number of "\
                          "devices per remote process.");
+    }
+
+    if (!mpqemu_msg_valid(msg)) {
+        error_setg(&err, "Message is not valid");
         goto finalize_loop;
     }
 
-- 
1.8.3.1