fix(acronc): input <cmd><EOF> will cause illegal memory access

Cause:
1. stdin got cmd -> request
2. stdin got EOF -> ac_disconnect -> ac_conn becomes NULL
3. socket got response -> ac_receive(ac_conn) -> crash

Conclusion: ordering issue between ac_disconnect and socket read.

Solution:

Best way: pause the input until command returns
Cons:
1. Lost the advantage of background execution of commands (has to wait until done)
2. It is unreliable to determine if a command is done: although the current server implementation will not send anything else after an error or cmd_result, Minecraft server itself or future server implementations may. The spec does not say anything on termination.
Acronc currently assumes that after receiving an error or cmd_result with the same request ID, it is done. Then, it resumes the stdin, reads the EOF, and then disconnect.

Worse way: Directly call uv_read_stop before ac_disconnect
Cons: It is going to lose anything, including command results. This is particularly undesirable for ad-hoc calls (i.e. echo list | acronc).

Therefore, the current approach is to block and read as much as we can (until error or cmd_result), then stop reading the socket before disconnecting as a double safe.

Signed-off-by: Trumeet <yuuta@yuuta.moe>

1 files changed, 9 insertions, 1 deletions

diff --git a/client/acronc/handler_stdin.c b/client/acronc/handler_stdin.c
index 3ac307d..4b8d0b8 100644
--- a/client/acronc/handler_stdin.c
+++ b/client/acronc/handler_stdin.c
@@ -74,12 +74,20 @@ static void on_stdin(uv_stream_t *t, ssize_t nread, const uv_buf_t *buf) {
     free(buf->base);
 }
 
+int stdin_start(void) {
+    return uv_read_start((uv_stream_t *) &tty, on_alloc, on_stdin);
+}
+
+void stdin_stop(void) {
+    uv_read_stop((uv_stream_t *) &tty);
+}
+
 int h_stdin(int (*on_input)(ac_request_t *req),
             void (*on_close)(void)) {
     cb_recv = on_input;
     cb_close = on_close;
     int r;
     if ((r = uv_tty_init(loop, &tty, 0, 0))) return r;
-    if ((r = uv_read_start((uv_stream_t *) &tty, on_alloc, on_stdin))) return r;
+    if ((r = stdin_start())) return r;
     return 0;
 }
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