There's a race condition in which the tcp_chr_read() ioc handler can
close a connection that is being written to from another thread.
Running iotest 136 in a loop triggers this problem and crashes QEMU.
(gdb) bt
#0 0x00005558b842902d in object_get_class (obj=0x0) at qom/object.c:860
#1 0x00005558b84f92db in qio_channel_writev_full (ioc=0x0,
iov=0x7ffc355decf0, niov=1, fds=0x0, nfds=0, errp=0x0) at io/channel.c:76
#2 0x00005558b84e0e9e in io_channel_send_full (ioc=0x0, buf=0x5558baf5beb0,
len=138, fds=0x0, nfds=0) at chardev/char-io.c:123
#3 0x00005558b84e4a69 in tcp_chr_write (chr=0x5558ba460380,
buf=0x5558baf5beb0 "...", len=138) at chardev/char-socket.c:135
#4 0x00005558b84dca55 in qemu_chr_write_buffer (s=0x5558ba460380,
buf=0x5558baf5beb0 "...", len=138, offset=0x7ffc355dedd0, write_all=false) at
chardev/char.c:112
#5 0x00005558b84dcbc2 in qemu_chr_write (s=0x5558ba460380, buf=0x5558baf5beb0
"...", len=138, write_all=false) at chardev/char.c:147
#6 0x00005558b84dfb26 in qemu_chr_fe_write (be=0x5558ba476610,
buf=0x5558baf5beb0 "...", len=138) at chardev/char-fe.c:42
#7 0x00005558b8088c86 in monitor_flush_locked (mon=0x5558ba476610) at
monitor.c:406
#8 0x00005558b8088e8c in monitor_puts (mon=0x5558ba476610, str=0x5558ba921e49
"") at monitor.c:449
#9 0x00005558b8089178 in qmp_send_response (mon=0x5558ba476610,
rsp=0x5558bb161600) at monitor.c:498
#10 0x00005558b808920c in monitor_qapi_event_emit (event=QAPI_EVENT_SHUTDOWN,
qdict=0x5558bb161600) at monitor.c:526
#11 0x00005558b8089307 in monitor_qapi_event_queue_no_reenter
(event=QAPI_EVENT_SHUTDOWN, qdict=0x5558bb161600) at monitor.c:551
#12 0x00005558b80896c0 in qapi_event_emit (event=QAPI_EVENT_SHUTDOWN,
qdict=0x5558bb161600) at monitor.c:626
#13 0x00005558b855f23b in qapi_event_send_shutdown (guest=false,
reason=SHUTDOWN_CAUSE_HOST_QMP_QUIT) at qapi/qapi-events-run-state.c:43
#14 0x00005558b81911ef in qemu_system_shutdown
(cause=SHUTDOWN_CAUSE_HOST_QMP_QUIT) at vl.c:1837
#15 0x00005558b8191308 in main_loop_should_exit () at vl.c:1885
#16 0x00005558b819140d in main_loop () at vl.c:1924
#17 0x00005558b8198c84 in main (argc=18, argv=0x7ffc355df3f8,
envp=0x7ffc355df490) at vl.c:4665
Signed-off-by: Alberto Garcia <be...@igalia.com>
---
chardev/char-socket.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index eaa8e8b68f..47bef1d2bd 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -148,7 +148,9 @@ static int tcp_chr_write(Chardev *chr, const uint8_t *buf,
int len)
if (ret < 0 && errno != EAGAIN) {
if (tcp_chr_read_poll(chr) <= 0) {
+ qemu_mutex_unlock(&chr->chr_write_lock);
tcp_chr_disconnect(chr);
+ qemu_mutex_lock(&chr->chr_write_lock);
return len;
} /* else let the read handler finish it properly */
}
@@ -449,7 +451,9 @@ static void tcp_chr_disconnect(Chardev *chr)
SocketChardev *s = SOCKET_CHARDEV(chr);
bool emit_close = s->connected;
+ qemu_mutex_lock(&chr->chr_write_lock);
tcp_chr_free_connection(chr);
+ qemu_mutex_unlock(&chr->chr_write_lock);
if (s->listener) {
qio_net_listener_set_client_func_full(s->listener, tcp_chr_accept,
--
2.11.0
