From 916eabd459fe707b5c4a86377d12e2ad1871b353 Mon Sep 17 00:00:00 2001 From: Kir Kolyshkin Date: Wed, 1 Aug 2018 07:03:55 +0300 Subject: [PATCH] daemon.ContainerLogs(): fix resource leak on follow When daemon.ContainerLogs() is called with options.follow=true (as in "docker logs --follow"), the "loggerutils.followLogs()" function never returns (even then the logs consumer is gone). As a result, all the resources associated with it (including an opened file descriptor for the log file being read, two FDs for a pipe, and two FDs for inotify watch) are never released. If this is repeated (such as by running "docker logs --follow" and pressing Ctrl-C a few times), this results in DoS caused by either hitting the limit of inotify watches, or the limit of opened files. The only cure is daemon restart. Apparently, what happens is: 1. logs producer (a container) is gone, calling (*LogWatcher).Close() for all its readers (daemon/logger/jsonfilelog/jsonfilelog.go:175). 2. WatchClose() is properly handled by a dedicated goroutine in followLogs(), cancelling the context. 3. Upon receiving the ctx.Done(), the code in followLogs() (daemon/logger/loggerutils/logfile.go#L626-L638) keeps to send messages _synchronously_ (which is OK for now). 4. Logs consumer is gone (Ctrl-C is pressed on a terminal running "docker logs --follow"). Method (*LogWatcher).Close() is properly called (see daemon/logs.go:114). Since it was called before and due to to once.Do(), nothing happens (which is kinda good, as otherwise it will panic on closing a closed channel). 5. A goroutine (see item 3 above) keeps sending log messages synchronously to the logWatcher.Msg channel. Since the channel reader is gone, the channel send operation blocks forever, and resource cleanup set up in defer statements at the beginning of followLogs() never happens. Alas, the fix is somewhat complicated: 1. Distinguish between close from logs producer and logs consumer. To that effect, - yet another channel is added to LogWatcher(); - {Watch,}Close() are renamed to {Watch,}ProducerGone(); - {Watch,}ConsumerGone() are added; *NOTE* that ProducerGone()/WatchProducerGone() pair is ONLY needed in order to stop ConsumerLogs(follow=true) when a container is stopped; otherwise we're not interested in it. In other words, we're only using it in followLogs(). 2. Code that was doing (logWatcher*).Close() is modified to either call ProducerGone() or ConsumerGone(), depending on the context. 3. Code that was waiting for WatchClose() is modified to wait for either ConsumerGone() or ProducerGone(), or both, depending on the context. 4. followLogs() are modified accordingly: - context cancellation is happening on WatchProducerGone(), and once it's received the FileWatcher is closed and waitRead() returns errDone on EOF (i.e. log rotation handling logic is disabled); - due to this, code that was writing synchronously to logWatcher.Msg can be and is removed as the code above it handles this case; - function returns once ConsumerGone is received, freeing all the resources -- this is the bugfix itself. While at it, 1. Let's also remove the ctx usage to simplify the code a bit. It was introduced by commit a69a59ffc7e3d ("Decouple removing the fileWatcher from reading") in order to fix a bug. The bug was actually a deadlock in fsnotify, and the fix was just a workaround. Since then the fsnofify bug has been fixed, and a new fsnotify was vendored in. For more details, please see https://github.com/moby/moby/pull/27782#issuecomment-416794490 2. Since `(*filePoller).Close()` is fixed to remove all the files being watched, there is no need to explicitly call fileWatcher.Remove(name) anymore, so get rid of the extra code. Should fix https://github.com/moby/moby/issues/37391 Signed-off-by: Kir Kolyshkin --- daemon/attach.go | 2 +- daemon/logger/adapter.go | 16 ++------ daemon/logger/adapter_test.go | 2 +- daemon/logger/journald/read.go | 4 +- daemon/logger/jsonfilelog/jsonfilelog.go | 5 ++- daemon/logger/jsonfilelog/read_test.go | 3 +- daemon/logger/local/local.go | 2 +- daemon/logger/logger.go | 47 +++++++++++++++-------- daemon/logger/loggerutils/logfile.go | 41 +++++--------------- daemon/logger/loggerutils/logfile_test.go | 4 +- daemon/logs.go | 4 +- 11 files changed, 58 insertions(+), 72 deletions(-) diff --git a/daemon/attach.go b/daemon/attach.go index fb14691d242af..0e12441ad1e2e 100644 --- a/daemon/attach.go +++ b/daemon/attach.go @@ -123,7 +123,7 @@ func (daemon *Daemon) containerAttach(c *container.Container, cfg *stream.Attach return logger.ErrReadLogsNotSupported{} } logs := cLog.ReadLogs(logger.ReadConfig{Tail: -1}) - defer logs.Close() + defer logs.ConsumerGone() LogLoop: for { diff --git a/daemon/logger/adapter.go b/daemon/logger/adapter.go index 95aff9bf3babc..d9370352c5735 100644 --- a/daemon/logger/adapter.go +++ b/daemon/logger/adapter.go @@ -93,21 +93,12 @@ func (a *pluginAdapterWithRead) ReadLogs(config ReadConfig) *LogWatcher { dec := logdriver.NewLogEntryDecoder(stream) for { - select { - case <-watcher.WatchClose(): - return - default: - } - var buf logdriver.LogEntry if err := dec.Decode(&buf); err != nil { if err == io.EOF { return } - select { - case watcher.Err <- errors.Wrap(err, "error decoding log message"): - case <-watcher.WatchClose(): - } + watcher.Err <- errors.Wrap(err, "error decoding log message") return } @@ -125,11 +116,10 @@ func (a *pluginAdapterWithRead) ReadLogs(config ReadConfig) *LogWatcher { return } + // send the message unless the consumer is gone select { case watcher.Msg <- msg: - case <-watcher.WatchClose(): - // make sure the message we consumed is sent - watcher.Msg <- msg + case <-watcher.WatchConsumerGone(): return } } diff --git a/daemon/logger/adapter_test.go b/daemon/logger/adapter_test.go index f47e711c892ea..d14a48e477627 100644 --- a/daemon/logger/adapter_test.go +++ b/daemon/logger/adapter_test.go @@ -174,7 +174,7 @@ func TestAdapterReadLogs(t *testing.T) { t.Fatal("timeout waiting for message channel to close") } - lw.Close() + lw.ProducerGone() lw = lr.ReadLogs(ReadConfig{Follow: true}) for _, x := range testMsg { diff --git a/daemon/logger/journald/read.go b/daemon/logger/journald/read.go index d4bcc62d9aefe..cadb97f4cabed 100644 --- a/daemon/logger/journald/read.go +++ b/daemon/logger/journald/read.go @@ -165,7 +165,7 @@ func (s *journald) Close() error { s.mu.Lock() s.closed = true for reader := range s.readers.readers { - reader.Close() + reader.ProducerGone() } s.mu.Unlock() return nil @@ -299,7 +299,7 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, j *C.sd_journal, // Wait until we're told to stop. select { case cursor = <-newCursor: - case <-logWatcher.WatchClose(): + case <-logWatcher.WatchConsumerGone(): // Notify the other goroutine that its work is done. C.close(pfd[1]) cursor = <-newCursor diff --git a/daemon/logger/jsonfilelog/jsonfilelog.go b/daemon/logger/jsonfilelog/jsonfilelog.go index 05243000d40d0..bbb8eeb7ec3a9 100644 --- a/daemon/logger/jsonfilelog/jsonfilelog.go +++ b/daemon/logger/jsonfilelog/jsonfilelog.go @@ -166,13 +166,14 @@ func ValidateLogOpt(cfg map[string]string) error { return nil } -// Close closes underlying file and signals all readers to stop. +// Close closes underlying file and signals all the readers +// that the logs producer is gone. func (l *JSONFileLogger) Close() error { l.mu.Lock() l.closed = true err := l.writer.Close() for r := range l.readers { - r.Close() + r.ProducerGone() delete(l.readers, r) } l.mu.Unlock() diff --git a/daemon/logger/jsonfilelog/read_test.go b/daemon/logger/jsonfilelog/read_test.go index 6ce4936e0e994..cfa8694b19ef9 100644 --- a/daemon/logger/jsonfilelog/read_test.go +++ b/daemon/logger/jsonfilelog/read_test.go @@ -50,11 +50,10 @@ func BenchmarkJSONFileLoggerReadLogs(b *testing.B) { }() lw := jsonlogger.(*JSONFileLogger).ReadLogs(logger.ReadConfig{Follow: true}) - watchClose := lw.WatchClose() for { select { case <-lw.Msg: - case <-watchClose: + case <-lw.WatchProducerGone(): return case err := <-chError: if err != nil { diff --git a/daemon/logger/local/local.go b/daemon/logger/local/local.go index 86c55784d4b10..ba4aa096f7104 100644 --- a/daemon/logger/local/local.go +++ b/daemon/logger/local/local.go @@ -166,7 +166,7 @@ func (d *driver) Close() error { d.closed = true err := d.logfile.Close() for r := range d.readers { - r.Close() + r.ProducerGone() delete(d.readers, r) } d.mu.Unlock() diff --git a/daemon/logger/logger.go b/daemon/logger/logger.go index 912e855c7f967..12e8d0054ec95 100644 --- a/daemon/logger/logger.go +++ b/daemon/logger/logger.go @@ -104,33 +104,50 @@ type LogWatcher struct { // For sending log messages to a reader. Msg chan *Message // For sending error messages that occur while while reading logs. - Err chan error - closeOnce sync.Once - closeNotifier chan struct{} + Err chan error + producerOnce sync.Once + producerGone chan struct{} + consumerOnce sync.Once + consumerGone chan struct{} } // NewLogWatcher returns a new LogWatcher. func NewLogWatcher() *LogWatcher { return &LogWatcher{ - Msg: make(chan *Message, logWatcherBufferSize), - Err: make(chan error, 1), - closeNotifier: make(chan struct{}), + Msg: make(chan *Message, logWatcherBufferSize), + Err: make(chan error, 1), + producerGone: make(chan struct{}), + consumerGone: make(chan struct{}), } } -// Close notifies the underlying log reader to stop. -func (w *LogWatcher) Close() { +// ProducerGone notifies the underlying log reader that +// the logs producer (a container) is gone. +func (w *LogWatcher) ProducerGone() { // only close if not already closed - w.closeOnce.Do(func() { - close(w.closeNotifier) + w.producerOnce.Do(func() { + close(w.producerGone) }) } -// WatchClose returns a channel receiver that receives notification -// when the watcher has been closed. This should only be called from -// one goroutine. -func (w *LogWatcher) WatchClose() <-chan struct{} { - return w.closeNotifier +// WatchProducerGone returns a channel receiver that receives notification +// once the logs producer (a container) is gone. +func (w *LogWatcher) WatchProducerGone() <-chan struct{} { + return w.producerGone +} + +// ConsumerGone notifies that the logs consumer is gone. +func (w *LogWatcher) ConsumerGone() { + // only close if not already closed + w.consumerOnce.Do(func() { + close(w.consumerGone) + }) +} + +// WatchConsumerGone returns a channel receiver that receives notification +// when the log watcher consumer is gone. +func (w *LogWatcher) WatchConsumerGone() <-chan struct{} { + return w.consumerGone } // Capability defines the list of capabilities that a driver can implement diff --git a/daemon/logger/loggerutils/logfile.go b/daemon/logger/loggerutils/logfile.go index a53190376e4bb..fa45154ec9765 100644 --- a/daemon/logger/loggerutils/logfile.go +++ b/daemon/logger/loggerutils/logfile.go @@ -488,7 +488,7 @@ func tailFiles(files []SizeReaderAt, watcher *logger.LogWatcher, createDecoder m go func() { select { case <-ctx.Done(): - case <-watcher.WatchClose(): + case <-watcher.WatchConsumerGone(): cancel() } }() @@ -546,22 +546,9 @@ func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan int } defer func() { f.Close() - fileWatcher.Remove(name) fileWatcher.Close() }() - ctx, cancel := context.WithCancel(context.Background()) - defer cancel() - go func() { - select { - case <-logWatcher.WatchClose(): - fileWatcher.Remove(name) - cancel() - case <-ctx.Done(): - return - } - }() - var retries int handleRotate := func() error { f.Close() @@ -596,7 +583,9 @@ func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan int case fsnotify.Rename, fsnotify.Remove: select { case <-notifyRotate: - case <-ctx.Done(): + case <-logWatcher.WatchProducerGone(): + return errDone + case <-logWatcher.WatchConsumerGone(): return errDone } if err := handleRotate(); err != nil { @@ -618,7 +607,9 @@ func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan int return errRetry } return err - case <-ctx.Done(): + case <-logWatcher.WatchProducerGone(): + return errDone + case <-logWatcher.WatchConsumerGone(): return errDone } } @@ -664,23 +655,11 @@ func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan int if !until.IsZero() && msg.Timestamp.After(until) { return } + // send the message, unless the consumer is gone select { case logWatcher.Msg <- msg: - case <-ctx.Done(): - logWatcher.Msg <- msg - for { - msg, err := decodeLogLine() - if err != nil { - return - } - if !since.IsZero() && msg.Timestamp.Before(since) { - continue - } - if !until.IsZero() && msg.Timestamp.After(until) { - return - } - logWatcher.Msg <- msg - } + case <-logWatcher.WatchConsumerGone(): + return } } } diff --git a/daemon/logger/loggerutils/logfile_test.go b/daemon/logger/loggerutils/logfile_test.go index c21aa258e6511..037592a3f2504 100644 --- a/daemon/logger/loggerutils/logfile_test.go +++ b/daemon/logger/loggerutils/logfile_test.go @@ -77,7 +77,7 @@ func TestTailFiles(t *testing.T) { } } -func TestFollowLogsClose(t *testing.T) { +func TestFollowLogsConsumerGone(t *testing.T) { lw := logger.NewLogWatcher() f, err := ioutil.TempFile("", t.Name()) @@ -110,7 +110,7 @@ func TestFollowLogsClose(t *testing.T) { t.Fatal("timeout waiting for log message") } - lw.Close() + lw.ConsumerGone() select { case <-followLogsDone: case <-time.After(20 * time.Second): diff --git a/daemon/logs.go b/daemon/logs.go index 5e5c34992eec6..668a75c778306 100644 --- a/daemon/logs.go +++ b/daemon/logs.go @@ -110,8 +110,8 @@ func (daemon *Daemon) ContainerLogs(ctx context.Context, containerName string, c } }() } - // set up some defers - defer logs.Close() + // signal that the log reader is gone + defer logs.ConsumerGone() // close the messages channel. closing is the only way to signal above // that we're doing with logs (other than context cancel i guess).