1 files changed, 33 insertions, 12 deletions

diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go
index 0b54c2e77..f4ddfa406 100644
--- a/pkg/sentry/fs/inode.go
+++ b/pkg/sentry/fs/inode.go
@@ -15,16 +15,18 @@
 package fs
 
 import (
-	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
-	"gvisor.googlesource.com/gvisor/pkg/log"
-	"gvisor.googlesource.com/gvisor/pkg/metric"
-	"gvisor.googlesource.com/gvisor/pkg/refs"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/lock"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
-	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"sync"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/metric"
+	"gvisor.dev/gvisor/pkg/refs"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 var opens = metric.MustCreateNewUint64Metric("/fs/opens", false /* sync */, "Number of file opens.")
@@ -55,6 +57,12 @@ type Inode struct {
 
 	// overlay is the overlay entry for this Inode.
 	overlay *overlayEntry
+
+	// appendMu is used to synchronize write operations into files which
+	// have been opened with O_APPEND. Operations which change a file size
+	// have to take this lock for read. Write operations to files with
+	// O_APPEND have to take this lock for write.
+	appendMu sync.RWMutex `state:"nosave"`
 }
 
 // LockCtx is an Inode's lock context and contains different personalities of locks; both
@@ -76,14 +84,16 @@ type LockCtx struct {
 // NewInode constructs an Inode from InodeOperations, a MountSource, and stable attributes.
 //
 // NewInode takes a reference on msrc.
-func NewInode(iops InodeOperations, msrc *MountSource, sattr StableAttr) *Inode {
+func NewInode(ctx context.Context, iops InodeOperations, msrc *MountSource, sattr StableAttr) *Inode {
 	msrc.IncRef()
-	return &Inode{
+	i := Inode{
 		InodeOperations: iops,
 		StableAttr:      sattr,
 		Watches:         newWatches(),
 		MountSource:     msrc,
 	}
+	i.EnableLeakCheck("fs.Inode")
+	return &i
 }
 
 // DecRef drops a reference on the Inode.
@@ -337,6 +347,8 @@ func (i *Inode) Truncate(ctx context.Context, d *Dirent, size int64) error {
 	if i.overlay != nil {
 		return overlayTruncate(ctx, i.overlay, d, size)
 	}
+	i.appendMu.RLock()
+	defer i.appendMu.RUnlock()
 	return i.InodeOperations.Truncate(ctx, i, size)
 }
 
@@ -438,3 +450,12 @@ func (i *Inode) CheckCapability(ctx context.Context, cp linux.Capability) bool {
 	}
 	return creds.HasCapability(cp)
 }
+
+func (i *Inode) lockAppendMu(appendMode bool) func() {
+	if appendMode {
+		i.appendMu.Lock()
+		return i.appendMu.Unlock
+	}
+	i.appendMu.RLock()
+	return i.appendMu.RUnlock
+}