Commit 3f0170505e for qemu.org

commit 3f0170505ee1953f44439b84fe3866d833cf37bf
Author: Fabiano Rosas <farosas@suse.de>
Date:   Fri Mar 6 09:01:12 2026 +0000

    chardev: Don't attempt to unregister yank function more than once

    tcp_chr_free_connection() can be called multiple times in succession,
    in which case the yank function will get as argument a NULL s->sioc
    that has been cleared by the previous tcp_chr_free_connection() call.

    This leads to an abort() at yank_unregister_function().

     #0  __GI_raise (sig=6) at ../sysdeps/unix/sysv/linux/raise.c:51
     #1  __GI_abort () at abort.c:79
     #2  qtest_check_status (s=0x513000005600) at ../tests/qtest/libqtest.c:209
     #3  qtest_wait_qemu (s=0x513000005600) at ../tests/qtest/libqtest.c:273
     #4  qtest_kill_qemu (s=0x513000005600) at ../tests/qtest/libqtest.c:285
     #5  kill_qemu_hook_func (s=0x513000005600) at ../tests/qtest/libqtest.c:294
     #6  g_hook_list_invoke (hook_list=0x55ea9cc750c0 <abrt_hooks>, may_recurse=0) at ../glib/ghook.c:534
     #7  sigabrt_handler (signo=6) at ../tests/qtest/libqtest.c:299
     #8  <signal handler called>
     #9  __GI_raise (sig=6) at ../sysdeps/unix/sysv/linux/raise.c:51
     #10 __GI_abort () at abort.c:79
     #11 yank_unregister_function (instance=0x7fb26f2ea9a0,
         func=0x55ea9bcc0a10 <char_socket_yank_iochannel>, opaque=0x0) at
         ../util/yank.c:151
     #12 tcp_chr_free_connection (chr=0x51300000ffc0) at ../chardev/char-socket.c:385
     #13 tcp_chr_disconnect_locked (chr=0x51300000ffc0) at ../chardev/char-socket.c:477
     #14 tcp_chr_disconnect (chr=0x51300000ffc0) at ../chardev/char-socket.c:495
     #15 tcp_chr_hup (channel=0x514000000040, cond=G_IO_HUP, opaque=0x51300000ffc0) at ../chardev/char-socket.c:536
     #16 qio_channel_fd_source_dispatch (source=0x50c0000b5fc0, callback=0x55ea9bcd6770 <tcp_chr_hup>,
         user_data=0x51300000ffc0) at ../io/channel-watch.c:84
     #17 g_main_dispatch (context=0x50f000000040) at ../glib/gmain.c:3381
     #18 g_main_context_dispatch (context=context@entry=0x50f000000040) at ../glib/gmain.c:4099
     #19 g_main_context_iterate (context=0x50f000000040, block=block@entry=1, dispatch=dispatch@entry=1,
         self=<optimized out>) at ../glib/gmain.c:4175
     #20 g_main_loop_run (loop=0x502000055690) at ../glib/gmain.c:4373

    Commit ebae6477dc ("chardev: check if the chardev is registered for
    yanking") seems to have encountered a similar issue, but checking
    s->registered_yank is not a complete solution because that flag
    pertains to the yank instance, not to each individual function.

    Skip the yank_unregister_function() in case s->sioc is already NULL,
    which indicates the last yank function was already removed.

    Signed-off-by: Fabiano Rosas <farosas@suse.de>
    Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
    Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
    Message-id: 20260302092225.4088227-7-peter.maydell@linaro.org
    [PMM: rebased]
    Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 5adeb90865..4e82915cf1 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -370,7 +370,8 @@ static void tcp_chr_free_connection(Chardev *chr)

     tcp_chr_set_msgfds(chr, NULL, 0);
     remove_fd_in_watch(chr);
-    if (s->registered_yank &&
+
+    if (s->registered_yank && s->sioc &&
         (s->state == TCP_CHARDEV_STATE_CONNECTING
         || s->state == TCP_CHARDEV_STATE_CONNECTED)) {
         yank_unregister_function(CHARDEV_YANK_INSTANCE(chr->label),