Serialize changing the state of the expiration manager pointer and

calling emitMetrics from its own goroutine.

Fixes #694

CHANGELOG.md

@@ -19,6 +19,7 @@ BUG FIXES:
  * core: Fix upgrade path for leases created in `generic` prior to 0.3 [GH-673]
  * core: Stale leader entries will now be reaped [GH-679]
  * core: Using `mount-tune` on the auth/token path did not take effect. [GH-688]
+ * core: Fix a potential race condition when (un)sealing the vault with metrics enabled [GH-694]
 
 MISC:
 

vault/core.go

@@ -17,10 +17,10 @@ import (
 	"golang.org/x/crypto/openpgp/packet"
 
 	"github.com/armon/go-metrics"
+	"github.com/hashicorp/uuid"
 	"github.com/hashicorp/vault/audit"
 	"github.com/hashicorp/vault/helper/mlock"
 	"github.com/hashicorp/vault/helper/pgpkeys"
-	"github.com/hashicorp/uuid"
 	"github.com/hashicorp/vault/logical"
 	"github.com/hashicorp/vault/physical"
 	"github.com/hashicorp/vault/shamir"
@@ -243,6 +243,10 @@ type Core struct {
 	// metricsCh is used to stop the metrics streaming
 	metricsCh chan struct{}
 
+	// metricsMutex is used to prevent a race condition between
+	// metrics emission and sealing leading to a nil pointer
+	metricsMutex sync.Mutex
+
 	defaultLeaseTTL time.Duration
 	maxLeaseTTL     time.Duration
 
@@ -1651,7 +1655,11 @@ func (c *Core) emitMetrics(stopCh chan struct{}) {
 	for {
 		select {
 		case <-time.After(time.Second):
-			c.expiration.emitMetrics()
+			c.metricsMutex.Lock()
+			if c.expiration != nil {
+				c.expiration.emitMetrics()
+			}
+			c.metricsMutex.Unlock()
 		case <-stopCh:
 			return
 		}

vault/expiration.go

@@ -77,6 +77,8 @@ func NewExpirationManager(router *Router, view *BarrierView, ts *TokenStore, log
 // setupExpiration is invoked after we've loaded the mount table to
 // initialize the expiration manager
 func (c *Core) setupExpiration() error {
+	c.metricsMutex.Lock()
+	defer c.metricsMutex.Unlock()
 	// Create a sub-view
 	view := c.systemBarrierView.SubView(expirationSubPath)
 
@@ -101,6 +103,8 @@ func (c *Core) stopExpiration() error {
 		if err := c.expiration.Stop(); err != nil {
 			return err
 		}
+		c.metricsMutex.Lock()
+		defer c.metricsMutex.Unlock()
 		c.expiration = nil
 	}
 	return nil