On one of our client's node, due to trying to read from closed ioc,
a segmentation fault occured. Corresponding backtrace:
0 object_get_class (obj=obj@entry=0x0)
1 qio_channel_readv_full (ioc=0x0, iov=0x7ffe55277180 ...
2 qio_channel_read (ioc=<optimized out> ...
3 vnc_client_read_buf (vs=vs@entry=0x55625f3c6000, ...
4 vnc_client_read_plain (vs=0x55625f3c6000)
5 vnc_client_read (vs=0x55625f3c6000)
6 vnc_client_io (ioc=<optimized out>, condition=G_IO_IN, ...
7 g_main_dispatch (context=0x556251568a50)
8 g_main_context_dispatch (context=context@entry=0x556251568a50)
9 glib_pollfds_poll ()
10 os_host_main_loop_wait (timeout=<optimized out>)
11 main_loop_wait (nonblocking=nonblocking@entry=0)
12 main_loop () at vl.c:1909
13 main (argc=<optimized out>, argv=<optimized out>, ...
Having analyzed the coredump, I understood that the reason is that
ioc_tag is reset on vnc_disconnect_start and ioc is cleaned
in vnc_disconnect_finish. Between these two events due to some
reasons the ioc_tag was set again and after vnc_disconnect_finish
the handler is running with freed ioc,
which led to the segmentation fault.
The patch checks vs->disconnecting in places where we call
qio_channel_add_watch and resets handler if disconnecting == TRUE
to prevent such an occurrence.
Signed-off-by: Klim Kireev <klim.kireev@virtuozzo.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20180207094844.21402-1-klim.kireev@virtuozzo.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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