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io: fix use after free in websocket handshake code

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If the QIOChannelWebsock object is freed while it is waiting to
complete a handshake, a GSource is leaked. This can lead to the
callback firing later on and triggering a use-after-free in the
use of the channel. This was observed in the VNC server with the
following trace from valgrind:

==2523108== Invalid read of size 4
==2523108==    at 0x4054A24: vnc_disconnect_start (vnc.c:1296)
==2523108==    by 0x4054A24: vnc_client_error (vnc.c:1392)
==2523108==    by 0x4068A09: vncws_handshake_done (vnc-ws.c:105)
==2523108==    by 0x44863B4: qio_task_complete (task.c:197)
==2523108==    by 0x448343D: qio_channel_websock_handshake_io (channel-websock.c:588)
==2523108==    by 0x6EDB862: UnknownInlinedFun (gmain.c:3398)
==2523108==    by 0x6EDB862: g_main_context_dispatch_unlocked.lto_priv.0 (gmain.c:4249)
==2523108==    by 0x6EDBAE4: g_main_context_dispatch (gmain.c:4237)
==2523108==    by 0x45EC79F: glib_pollfds_poll (main-loop.c:287)
==2523108==    by 0x45EC79F: os_host_main_loop_wait (main-loop.c:310)
==2523108==    by 0x45EC79F: main_loop_wait (main-loop.c:589)
==2523108==    by 0x423A56D: qemu_main_loop (runstate.c:835)
==2523108==    by 0x454F300: qemu_default_main (main.c:37)
==2523108==    by 0x73D6574: (below main) (libc_start_call_main.h:58)
==2523108==  Address 0x57a6e0dc is 28 bytes inside a block of size 103,608 free'd
==2523108==    at 0x5F2FE43: free (vg_replace_malloc.c:989)
==2523108==    by 0x6EDC444: g_free (gmem.c:208)
==2523108==    by 0x4053F23: vnc_update_client (vnc.c:1153)
==2523108==    by 0x4053F23: vnc_refresh (vnc.c:3225)
==2523108==    by 0x4042881: dpy_refresh (console.c:880)
==2523108==    by 0x4042881: gui_update (console.c:90)
==2523108==    by 0x45EFA1B: timerlist_run_timers.part.0 (qemu-timer.c:562)
==2523108==    by 0x45EFC8F: timerlist_run_timers (qemu-timer.c:495)
==2523108==    by 0x45EFC8F: qemu_clock_run_timers (qemu-timer.c:576)
==2523108==    by 0x45EFC8F: qemu_clock_run_all_timers (qemu-timer.c:663)
==2523108==    by 0x45EC765: main_loop_wait (main-loop.c:600)
==2523108==    by 0x423A56D: qemu_main_loop (runstate.c:835)
==2523108==    by 0x454F300: qemu_default_main (main.c:37)
==2523108==    by 0x73D6574: (below main) (libc_start_call_main.h:58)
==2523108==  Block was alloc'd at
==2523108==    at 0x5F343F3: calloc (vg_replace_malloc.c:1675)
==2523108==    by 0x6EE2F81: g_malloc0 (gmem.c:133)
==2523108==    by 0x4057DA3: vnc_connect (vnc.c:3245)
==2523108==    by 0x448591B: qio_net_listener_channel_func (net-listener.c:54)
==2523108==    by 0x6EDB862: UnknownInlinedFun (gmain.c:3398)
==2523108==    by 0x6EDB862: g_main_context_dispatch_unlocked.lto_priv.0 (gmain.c:4249)
==2523108==    by 0x6EDBAE4: g_main_context_dispatch (gmain.c:4237)
==2523108==    by 0x45EC79F: glib_pollfds_poll (main-loop.c:287)
==2523108==    by 0x45EC79F: os_host_main_loop_wait (main-loop.c:310)
==2523108==    by 0x45EC79F: main_loop_wait (main-loop.c:589)
==2523108==    by 0x423A56D: qemu_main_loop (runstate.c:835)
==2523108==    by 0x454F300: qemu_default_main (main.c:37)
==2523108==    by 0x73D6574: (below main) (libc_start_call_main.h:58)
==2523108==

The above can be reproduced by launching QEMU with

  $ qemu-system-x86_64 -vnc localhost:0,websocket=5700

and then repeatedly running:

  for i in {1..100}; do
     (echo -n "GET / HTTP/1.1" && sleep 0.05) | nc -w 1 localhost 5700 &
  done

CVE-2025-11234
Reported-by: Grant Millar | Cylo <rid@cylo.io>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrangé
2025-09-30 12:03:15 +01:00
parent 322c3c4f3a
commit b7a1f2ca45
2 changed files with 18 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
include/io/channel-websock.h
View File

@ -61,7 +61,8 @@ struct QIOChannelWebsock {
size_t payload_remain;
size_t pong_remain;
QIOChannelWebsockMask mask;
guint io_tag;
guint hs_io_tag; /* tracking handshake task */
guint io_tag; /* tracking watch task */
Error *io_err;
gboolean io_eof;
uint8_t opcode;

22
io/channel-websock.c
View File

@ -545,6 +545,7 @@ static gboolean qio_channel_websock_handshake_send(QIOChannel *ioc,
trace_qio_channel_websock_handshake_fail(ioc, error_get_pretty(err));
qio_task_set_error(task, err);
qio_task_complete(task);
wioc->hs_io_tag = 0;
return FALSE;
}
@ -560,6 +561,7 @@ static gboolean qio_channel_websock_handshake_send(QIOChannel *ioc,
trace_qio_channel_websock_handshake_complete(ioc);
qio_task_complete(task);
}
wioc->hs_io_tag = 0;
return FALSE;
}
trace_qio_channel_websock_handshake_pending(ioc, G_IO_OUT);
@ -586,6 +588,7 @@ static gboolean qio_channel_websock_handshake_io(QIOChannel *ioc,
trace_qio_channel_websock_handshake_fail(ioc, error_get_pretty(err));
qio_task_set_error(task, err);
qio_task_complete(task);
wioc->hs_io_tag = 0;
return FALSE;
}
if (ret == 0) {
@ -597,7 +600,7 @@ static gboolean qio_channel_websock_handshake_io(QIOChannel *ioc,
error_propagate(&wioc->io_err, err);
trace_qio_channel_websock_handshake_reply(ioc);
qio_channel_add_watch(
wioc->hs_io_tag = qio_channel_add_watch(
wioc->master,
G_IO_OUT,
qio_channel_websock_handshake_send,
@ -907,11 +910,12 @@ void qio_channel_websock_handshake(QIOChannelWebsock *ioc,
trace_qio_channel_websock_handshake_start(ioc);
trace_qio_channel_websock_handshake_pending(ioc, G_IO_IN);
qio_channel_add_watch(ioc->master,
G_IO_IN,
qio_channel_websock_handshake_io,
task,
NULL);
ioc->hs_io_tag = qio_channel_add_watch(
ioc->master,
G_IO_IN,
qio_channel_websock_handshake_io,
task,
NULL);
}
@ -922,6 +926,9 @@ static void qio_channel_websock_finalize(Object *obj)
buffer_free(&ioc->encinput);
buffer_free(&ioc->encoutput);
buffer_free(&ioc->rawinput);
if (ioc->hs_io_tag) {
g_source_remove(ioc->hs_io_tag);
}
if (ioc->io_tag) {
g_source_remove(ioc->io_tag);
}
@ -1221,6 +1228,9 @@ static int qio_channel_websock_close(QIOChannel *ioc,
buffer_free(&wioc->encinput);
buffer_free(&wioc->encoutput);
buffer_free(&wioc->rawinput);
if (wioc->hs_io_tag) {
g_clear_handle_id(&wioc->hs_io_tag, g_source_remove);
}
if (wioc->io_tag) {
g_clear_handle_id(&wioc->io_tag, g_source_remove);
}