--- /dev/null
+From aec6bba73f7d7692de2c4196ee80e4d753b45604 Mon Sep 17 00:00:00 2001
+From: Stefan Hajnoczi <stefanha@redhat.com>
+Date: Fri, 2 Jun 2017 10:54:24 +0100
+Subject: [PATCH 02/13] virtio-serial: fix segfault on disconnect
+
+Since commit d4c19cdeeb2f1e474bc426a6da261f1d7346eb5b ("virtio-serial:
+add missing virtio_detach_element() call") the following commands may
+cause QEMU to segfault:
+
+ $ qemu -M accel=kvm -cpu host -m 1G \
+ -drive if=virtio,file=test.img,format=raw \
+ -device virtio-serial-pci,id=virtio-serial0 \
+ -chardev socket,id=channel1,path=/tmp/chardev.sock,server,nowait \
+ -device virtserialport,chardev=channel1,bus=virtio-serial0.0,id=port1
+ $ nc -U /tmp/chardev.sock
+ ^C
+
+ (guest)$ cat /dev/zero >/dev/vport0p1
+
+The segfault is non-deterministic: if the event loop notices the socket
+has been closed then there is no crash. The disconnect has to happen
+right before QEMU attempts to write data to the socket.
+
+The backtrace is as follows:
+
+ Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
+ 0x00005555557e0698 in do_flush_queued_data (port=0x5555582cedf0, vq=0x7fffcc854290, vdev=0x55555807b1d0) at hw/char/virtio-serial-bus.c:180
+ 180 for (i = port->iov_idx; i < port->elem->out_num; i++) {
+ #1 0x000055555580d363 in virtio_queue_notify_vq (vq=0x7fffcc854290) at hw/virtio/virtio.c:1524
+ #2 0x000055555580d363 in virtio_queue_host_notifier_read (n=0x7fffcc8542f8) at hw/virtio/virtio.c:2430
+ #3 0x0000555555b3482c in aio_dispatch_handlers (ctx=ctx@entry=0x5555566b8c80) at util/aio-posix.c:399
+ #4 0x0000555555b350d8 in aio_dispatch (ctx=0x5555566b8c80) at util/aio-posix.c:430
+ #5 0x0000555555b3212e in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at util/async.c:261
+ #6 0x00007fffde71de52 in g_main_context_dispatch () at /lib64/libglib-2.0.so.0
+ #7 0x0000555555b34353 in glib_pollfds_poll () at util/main-loop.c:213
+ #8 0x0000555555b34353 in os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:261
+ #9 0x0000555555b34353 in main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:517
+ #10 0x0000555555773207 in main_loop () at vl.c:1917
+ #11 0x0000555555773207 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4751
+
+The do_flush_queued_data() function does not anticipate chardev close
+events during vsc->have_data(). It expects port->elem to remain
+non-NULL for the duration its for loop.
+
+The fix is simply to return from do_flush_queued_data() if the port
+closes because the close event already frees port->elem and drains the
+virtqueue - there is nothing left for do_flush_queued_data() to do.
+
+Reported-by: Sitong Liu <siliu@redhat.com>
+Reported-by: Min Deng <mdeng@redhat.com>
+Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
+Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
+Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
+---
+ hw/char/virtio-serial-bus.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
+index aa9c11ae92..f5bc173844 100644
+--- a/hw/char/virtio-serial-bus.c
++++ b/hw/char/virtio-serial-bus.c
+@@ -186,6 +186,9 @@ static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
+ port->elem->out_sg[i].iov_base
+ + port->iov_offset,
+ buf_size);
++ if (!port->elem) { /* bail if we got disconnected */
++ return;
++ }
+ if (port->throttled) {
+ port->iov_idx = i;
+ if (ret > 0) {
+--
+2.11.0
+
projects / pve-qemu.git / blobdiff