| Message ID | 1565625509-404969-3-git-send-email-andrey.shinkevich@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | char-socket: Fix race condition | expand |
On Mon, Aug 12, 2019 at 06:58:29PM +0300, Andrey Shinkevich wrote: > From: Alberto Garcia <berto@igalia.com> > > 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 > > This patch adds a lock to protect tcp_chr_disconnect() and > socket_reconnect_timeout() > > Signed-off-by: Alberto Garcia <berto@igalia.com> > Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Regards, Daniel
On 20/08/2019 12:58, Daniel P. Berrangé wrote: > On Mon, Aug 12, 2019 at 06:58:29PM +0300, Andrey Shinkevich wrote: >> From: Alberto Garcia <berto@igalia.com> >> >> 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 >> >> This patch adds a lock to protect tcp_chr_disconnect() and >> socket_reconnect_timeout() >> >> Signed-off-by: Alberto Garcia <berto@igalia.com> >> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> > > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> > > > Regards, > Daniel > Thank you Daniel Andrey
diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 7ca5d97..03f0340 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -150,7 +150,7 @@ static void tcp_chr_accept(QIONetListener *listener, void *opaque); static int tcp_chr_read_poll(void *opaque); -static void tcp_chr_disconnect(Chardev *chr); +static void tcp_chr_disconnect_locked(Chardev *chr); /* Called with chr_write_lock held. */ static int tcp_chr_write(Chardev *chr, const uint8_t *buf, int len) @@ -174,7 +174,7 @@ 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) { - tcp_chr_disconnect(chr); + tcp_chr_disconnect_locked(chr); return len; } /* else let the read handler finish it properly */ } @@ -469,8 +469,9 @@ static void update_disconnected_filename(SocketChardev *s) /* NB may be called even if tcp_chr_connect has not been * reached, due to TLS or telnet initialization failure, * so can *not* assume s->state == TCP_CHARDEV_STATE_CONNECTED + * This must be called with chr->chr_write_lock held. */ -static void tcp_chr_disconnect(Chardev *chr) +static void tcp_chr_disconnect_locked(Chardev *chr) { SocketChardev *s = SOCKET_CHARDEV(chr); bool emit_close = s->state == TCP_CHARDEV_STATE_CONNECTED; @@ -490,6 +491,13 @@ static void tcp_chr_disconnect(Chardev *chr) } } +static void tcp_chr_disconnect(Chardev *chr) +{ + qemu_mutex_lock(&chr->chr_write_lock); + tcp_chr_disconnect_locked(chr); + qemu_mutex_unlock(&chr->chr_write_lock); +} + static gboolean tcp_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque) { Chardev *chr = CHARDEV(opaque); @@ -1131,8 +1139,10 @@ static gboolean socket_reconnect_timeout(gpointer opaque) Chardev *chr = CHARDEV(opaque); SocketChardev *s = SOCKET_CHARDEV(opaque); + qemu_mutex_lock(&chr->chr_write_lock); g_source_unref(s->reconnect_timer); s->reconnect_timer = NULL; + qemu_mutex_unlock(&chr->chr_write_lock); if (chr->be_open) { return false;