[Qemu-devel] [PATCH v2 1/1] virtio-console: Prevent abort()s in case of host chardev close

[Amit Shah <amit.shah@redhat.com>]

A host chardev could close just before the guest sends some data to be
written.  This will cause an -EPIPE error.  This shouldn't be propagated
to virtio-serial-bus.

Ideally we should close the port once -EPIPE is received, but since the
chardev interface doesn't return such meaningful values to its users,
all we get is -1 for any kind of error.  Just return 0 for now and wait
for chardevs to return better error messages to act better on the return
messages.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 hw/virtio-console.c |   20 ++++++++++++++++++--
 1 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/hw/virtio-console.c b/hw/virtio-console.c
index b076331..9ca0dc6 100644
--- a/hw/virtio-console.c
+++ b/hw/virtio-console.c
@@ -24,8 +24,24 @@ typedef struct VirtConsole {
 static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
 {
     VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
-
-    return qemu_chr_write(vcon->chr, buf, len);
+    ssize_t ret;
+
+    ret = qemu_chr_write(vcon->chr, buf, len);
+    if (ret < 0) {
+        /*
+         * Ideally we'd get a better error code than just -1, but
+         * that's what the chardev interface gives us right now.  If
+         * we had a finer-grained message, like -EPIPE, we could close
+         * this connection.  Absent such error messages, the most we
+         * can do is to return 0 here.
+         *
+         * This will prevent stray -1 values to go to
+         * virtio-serial-bus.c and cause abort()s in
+         * do_flush_queued_data().
+         */
+        ret = 0;
+    }
+    return ret;
 }
 
 /* Callback function that's called when the guest opens the port */
-- 
1.7.6