From 51822f722a033a481a5e0edcc51e33f5c39e9369 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 18 Mar 2019 12:49:25 -0600 Subject: [PATCH] ringlogger: document races Signed-off-by: Jason A. Donenfeld --- WireGuard/Shared/Logging/ringlogger.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/WireGuard/Shared/Logging/ringlogger.c b/WireGuard/Shared/Logging/ringlogger.c index 440a269..563483a 100644 --- a/WireGuard/Shared/Logging/ringlogger.c +++ b/WireGuard/Shared/Logging/ringlogger.c @@ -42,11 +42,14 @@ void write_msg_to_log(struct log *log, const char *tag, const char *msg) struct log_line *line; struct timespec ts; + // Race: This isn't synchronized with the fetch_add below, so items might be slightly out of order. clock_gettime(CLOCK_REALTIME, &ts); + // Race: More than MAX_LINES writers and this will clash. index = atomic_fetch_add(&log->next_index, 1); line = &log->lines[index % MAX_LINES]; + // Race: Before this line executes, we'll display old data after new data. atomic_store(&line->time_ns, 0); memset(line->line, 0, MAX_LOG_LINE_LENGTH);