Merge release-20200907.0-129-g319d1b8ba (automated)

38 files changed, 145 insertions, 118 deletions

diff --git a/pkg/sentry/fsimpl/devpts/root_inode_refs.go b/pkg/sentry/fsimpl/devpts/root_inode_refs.go
index 1b7090229..b860819f0 100644
--- a/pkg/sentry/fsimpl/devpts/root_inode_refs.go
+++ b/pkg/sentry/fsimpl/devpts/root_inode_refs.go
@@ -1,12 +1,12 @@
 package devpts
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/fuse/inode_refs.go b/pkg/sentry/fsimpl/fuse/inode_refs.go
index 12e7d6e6c..646042846 100644
--- a/pkg/sentry/fsimpl/fuse/inode_refs.go
+++ b/pkg/sentry/fsimpl/fuse/inode_refs.go
@@ -1,12 +1,12 @@
 package fuse
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/gofer/filesystem.go b/pkg/sentry/fsimpl/gofer/filesystem.go
index b01121f9e..4a592175b 100644
--- a/pkg/sentry/fsimpl/gofer/filesystem.go
+++ b/pkg/sentry/fsimpl/gofer/filesystem.go
@@ -1026,7 +1026,7 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, opts *vfs.Open
 		// step is required even if !d.cachedMetadataAuthoritative() because
 		// d.mappings has to be updated.
 		// d.metadataMu has already been acquired if trunc == true.
-		d.updateFileSizeLocked(0)
+		d.updateSizeLocked(0)
 
 		if d.cachedMetadataAuthoritative() {
 			d.touchCMtimeLocked()
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 0e21c31a4..aaad9c0d9 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -833,7 +833,7 @@ func (d *dentry) updateFromP9AttrsLocked(mask p9.AttrMask, attr *p9.Attr) {
 		atomic.StoreUint32(&d.nlink, uint32(attr.NLink))
 	}
 	if mask.Size {
-		d.updateFileSizeLocked(attr.Size)
+		d.updateSizeLocked(attr.Size)
 	}
 }
 
@@ -987,7 +987,7 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs
 				// d.size should be kept up to date, and privatized
 				// copy-on-write mappings of truncated pages need to be
 				// invalidated, even if InteropModeShared is in effect.
-				d.updateFileSizeLocked(stat.Size)
+				d.updateSizeLocked(stat.Size)
 			}
 		}
 		if d.fs.opts.interop == InteropModeShared {
@@ -1024,8 +1024,31 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs
 	return nil
 }
 
+// doAllocate performs an allocate operation on d. Note that d.metadataMu will
+// be held when allocate is called.
+func (d *dentry) doAllocate(ctx context.Context, offset, length uint64, allocate func() error) error {
+	d.metadataMu.Lock()
+	defer d.metadataMu.Unlock()
+
+	// Allocating a smaller size is a noop.
+	size := offset + length
+	if d.cachedMetadataAuthoritative() && size <= d.size {
+		return nil
+	}
+
+	err := allocate()
+	if err != nil {
+		return err
+	}
+	d.updateSizeLocked(size)
+	if d.cachedMetadataAuthoritative() {
+		d.touchCMtimeLocked()
+	}
+	return nil
+}
+
 // Preconditions: d.metadataMu must be locked.
-func (d *dentry) updateFileSizeLocked(newSize uint64) {
+func (d *dentry) updateSizeLocked(newSize uint64) {
 	d.dataMu.Lock()
 	oldSize := d.size
 	atomic.StoreUint64(&d.size, newSize)
diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go
index a2e9342d5..24f03ee94 100644
--- a/pkg/sentry/fsimpl/gofer/regular_file.go
+++ b/pkg/sentry/fsimpl/gofer/regular_file.go
@@ -79,28 +79,11 @@ func (fd *regularFileFD) OnClose(ctx context.Context) error {
 // Allocate implements vfs.FileDescriptionImpl.Allocate.
 func (fd *regularFileFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
 	d := fd.dentry()
-	d.metadataMu.Lock()
-	defer d.metadataMu.Unlock()
-
-	// Allocating a smaller size is a noop.
-	size := offset + length
-	if d.cachedMetadataAuthoritative() && size <= d.size {
-		return nil
-	}
-
-	d.handleMu.RLock()
-	err := d.writeFile.allocate(ctx, p9.ToAllocateMode(mode), offset, length)
-	d.handleMu.RUnlock()
-	if err != nil {
-		return err
-	}
-	d.dataMu.Lock()
-	atomic.StoreUint64(&d.size, size)
-	d.dataMu.Unlock()
-	if d.cachedMetadataAuthoritative() {
-		d.touchCMtimeLocked()
-	}
-	return nil
+	return d.doAllocate(ctx, offset, length, func() error {
+		d.handleMu.RLock()
+		defer d.handleMu.RUnlock()
+		return d.writeFile.allocate(ctx, p9.ToAllocateMode(mode), offset, length)
+	})
 }
 
 // PRead implements vfs.FileDescriptionImpl.PRead.
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index 3c39aa9b7..dc960e5bf 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fdnotifier"
+	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -135,6 +136,16 @@ func (fd *specialFileFD) EventUnregister(e *waiter.Entry) {
 	fd.fileDescription.EventUnregister(e)
 }
 
+func (fd *specialFileFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
+	if fd.isRegularFile {
+		d := fd.dentry()
+		return d.doAllocate(ctx, offset, length, func() error {
+			return fd.handle.file.allocate(ctx, p9.ToAllocateMode(mode), offset, length)
+		})
+	}
+	return fd.FileDescriptionDefaultImpl.Allocate(ctx, mode, offset, length)
+}
+
 // PRead implements vfs.FileDescriptionImpl.PRead.
 func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	if fd.seekable && offset < 0 {
diff --git a/pkg/sentry/fsimpl/host/connected_endpoint_refs.go b/pkg/sentry/fsimpl/host/connected_endpoint_refs.go
index 7fa5a516d..670166c76 100644
--- a/pkg/sentry/fsimpl/host/connected_endpoint_refs.go
+++ b/pkg/sentry/fsimpl/host/connected_endpoint_refs.go
@@ -1,12 +1,12 @@
 package host
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go
index 1bd0e4ee8..c4551562a 100644
--- a/pkg/sentry/fsimpl/host/host.go
+++ b/pkg/sentry/fsimpl/host/host.go
@@ -560,12 +560,7 @@ func (f *fileDescription) Release(context.Context) {
 
 // Allocate implements vfs.FileDescriptionImpl.
 func (f *fileDescription) Allocate(ctx context.Context, mode, offset, length uint64) error {
-	if !f.inode.seekable {
-		return syserror.ESPIPE
-	}
-
-	// TODO(gvisor.dev/issue/3589): Implement Allocate for non-pipe hostfds.
-	return syserror.EOPNOTSUPP
+	return unix.Fallocate(f.inode.hostFD, uint32(mode), int64(offset), int64(length))
 }
 
 // PRead implements FileDescriptionImpl.
diff --git a/pkg/sentry/fsimpl/host/inode_refs.go b/pkg/sentry/fsimpl/host/inode_refs.go
index c294b8b80..49c57c113 100644
--- a/pkg/sentry/fsimpl/host/inode_refs.go
+++ b/pkg/sentry/fsimpl/host/inode_refs.go
@@ -1,12 +1,12 @@
 package host
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/kernfs/dentry_refs.go b/pkg/sentry/fsimpl/kernfs/dentry_refs.go
index dd5325635..0269851c9 100644
--- a/pkg/sentry/fsimpl/kernfs/dentry_refs.go
+++ b/pkg/sentry/fsimpl/kernfs/dentry_refs.go
@@ -1,12 +1,12 @@
 package kernfs
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/kernfs/static_directory_refs.go b/pkg/sentry/fsimpl/kernfs/static_directory_refs.go
index 80513f6aa..866620ef9 100644
--- a/pkg/sentry/fsimpl/kernfs/static_directory_refs.go
+++ b/pkg/sentry/fsimpl/kernfs/static_directory_refs.go
@@ -1,12 +1,12 @@
 package kernfs
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/overlay/non_directory.go b/pkg/sentry/fsimpl/overlay/non_directory.go
index 74cfd3799..6e04705c7 100644
--- a/pkg/sentry/fsimpl/overlay/non_directory.go
+++ b/pkg/sentry/fsimpl/overlay/non_directory.go
@@ -147,6 +147,16 @@ func (fd *nonDirectoryFD) Stat(ctx context.Context, opts vfs.StatOptions) (linux
 	return stat, nil
 }
 
+// Allocate implements vfs.FileDescriptionImpl.Allocate.
+func (fd *nonDirectoryFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
+	wrappedFD, err := fd.getCurrentFD(ctx)
+	if err != nil {
+		return err
+	}
+	defer wrappedFD.DecRef(ctx)
+	return wrappedFD.Allocate(ctx, mode, offset, length)
+}
+
 // SetStat implements vfs.FileDescriptionImpl.SetStat.
 func (fd *nonDirectoryFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) error {
 	d := fd.dentry()
diff --git a/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go b/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go
index 8ed286c46..84c03e6cd 100644
--- a/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go
@@ -1,12 +1,12 @@
 package proc
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go b/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go
index 957c6a6dd..5b3c7cd1c 100644
--- a/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go
@@ -1,12 +1,12 @@
 package proc
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go b/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go
index a80ec9e0a..3091deb89 100644
--- a/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go
@@ -1,12 +1,12 @@
 package proc
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/proc/task_inode_refs.go b/pkg/sentry/fsimpl/proc/task_inode_refs.go
index c4835cbca..5833527c5 100644
--- a/pkg/sentry/fsimpl/proc/task_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/task_inode_refs.go
@@ -1,12 +1,12 @@
 package proc
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/proc/tasks_inode_refs.go b/pkg/sentry/fsimpl/proc/tasks_inode_refs.go
index 5dfb34238..0961dd629 100644
--- a/pkg/sentry/fsimpl/proc/tasks_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/tasks_inode_refs.go
@@ -1,12 +1,12 @@
 package proc
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/sys/dir_refs.go b/pkg/sentry/fsimpl/sys/dir_refs.go
index c05154e2b..718d542eb 100644
--- a/pkg/sentry/fsimpl/sys/dir_refs.go
+++ b/pkg/sentry/fsimpl/sys/dir_refs.go
@@ -1,12 +1,12 @@
 package sys
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/fsimpl/tmpfs/inode_refs.go b/pkg/sentry/fsimpl/tmpfs/inode_refs.go
index 38cc30981..5ec208d9e 100644
--- a/pkg/sentry/fsimpl/tmpfs/inode_refs.go
+++ b/pkg/sentry/fsimpl/tmpfs/inode_refs.go
@@ -1,12 +1,12 @@
 package tmpfs
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/kernel/fd_table_refs.go b/pkg/sentry/kernel/fd_table_refs.go
index 8973cac8a..9330e37e4 100644
--- a/pkg/sentry/kernel/fd_table_refs.go
+++ b/pkg/sentry/kernel/fd_table_refs.go
@@ -1,12 +1,12 @@
 package kernel
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/kernel/fs_context_refs.go b/pkg/sentry/kernel/fs_context_refs.go
index c0e01dbb3..e2280f400 100644
--- a/pkg/sentry/kernel/fs_context_refs.go
+++ b/pkg/sentry/kernel/fs_context_refs.go
@@ -1,12 +1,12 @@
 package kernel
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/kernel/pipe/vfs.go b/pkg/sentry/kernel/pipe/vfs.go
index f223d59e1..f61039f5b 100644
--- a/pkg/sentry/kernel/pipe/vfs.go
+++ b/pkg/sentry/kernel/pipe/vfs.go
@@ -67,6 +67,11 @@ func (vp *VFSPipe) ReaderWriterPair(mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlag
 	return vp.newFD(mnt, vfsd, linux.O_RDONLY|statusFlags, locks), vp.newFD(mnt, vfsd, linux.O_WRONLY|statusFlags, locks)
 }
 
+// Allocate implements vfs.FileDescriptionImpl.Allocate.
+func (*VFSPipe) Allocate(context.Context, uint64, uint64, uint64) error {
+	return syserror.ESPIPE
+}
+
 // Open opens the pipe represented by vp.
 func (vp *VFSPipe) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlags uint32, locks *vfs.FileLocks) (*vfs.FileDescription, error) {
 	vp.mu.Lock()
diff --git a/pkg/sentry/kernel/process_group_refs.go b/pkg/sentry/kernel/process_group_refs.go
index 5ff83ab96..832a99d66 100644
--- a/pkg/sentry/kernel/process_group_refs.go
+++ b/pkg/sentry/kernel/process_group_refs.go
@@ -1,12 +1,12 @@
 package kernel
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo_unsafe.go b/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo_unsafe.go
index 90148bbb2..a37f74a10 100644
--- a/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo_unsafe.go
+++ b/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo_unsafe.go
@@ -2,11 +2,10 @@ package kernel
 
 import (
 	"fmt"
+	"gvisor.dev/gvisor/pkg/sync"
 	"reflect"
 	"strings"
 	"unsafe"
-
-	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
diff --git a/pkg/sentry/kernel/session_refs.go b/pkg/sentry/kernel/session_refs.go
index 9c51eda6c..850f56d3a 100644
--- a/pkg/sentry/kernel/session_refs.go
+++ b/pkg/sentry/kernel/session_refs.go
@@ -1,12 +1,12 @@
 package kernel
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/kernel/shm/shm_refs.go b/pkg/sentry/kernel/shm/shm_refs.go
index 0da23fa5f..35f74eb6c 100644
--- a/pkg/sentry/kernel/shm/shm_refs.go
+++ b/pkg/sentry/kernel/shm/shm_refs.go
@@ -1,12 +1,12 @@
 package shm
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/mm/aio_mappable_refs.go b/pkg/sentry/mm/aio_mappable_refs.go
index c80c56d94..d4f278400 100644
--- a/pkg/sentry/mm/aio_mappable_refs.go
+++ b/pkg/sentry/mm/aio_mappable_refs.go
@@ -1,12 +1,12 @@
 package mm
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/mm/special_mappable_refs.go b/pkg/sentry/mm/special_mappable_refs.go
index 5eb7e69e0..2a348bacf 100644
--- a/pkg/sentry/mm/special_mappable_refs.go
+++ b/pkg/sentry/mm/special_mappable_refs.go
@@ -1,12 +1,12 @@
 package mm
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/platform/ring0/defs_impl_arm64.go b/pkg/sentry/platform/ring0/defs_impl_arm64.go
index 6b06983ba..78547069f 100644
--- a/pkg/sentry/platform/ring0/defs_impl_arm64.go
+++ b/pkg/sentry/platform/ring0/defs_impl_arm64.go
@@ -3,11 +3,11 @@ package ring0
 import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
-	"reflect"
 
 	"fmt"
 	"gvisor.dev/gvisor/pkg/usermem"
 	"io"
+	"reflect"
 )
 
 // Useful bits.
diff --git a/pkg/sentry/socket/hostinet/socket_vfs2.go b/pkg/sentry/socket/hostinet/socket_vfs2.go
index 8a1d52ebf..97bc6027f 100644
--- a/pkg/sentry/socket/hostinet/socket_vfs2.go
+++ b/pkg/sentry/socket/hostinet/socket_vfs2.go
@@ -97,11 +97,6 @@ func (s *socketVFS2) Ioctl(ctx context.Context, uio usermem.IO, args arch.Syscal
 	return ioctl(ctx, s.fd, uio, args)
 }
 
-// Allocate implements vfs.FileDescriptionImpl.Allocate.
-func (s *socketVFS2) Allocate(ctx context.Context, mode, offset, length uint64) error {
-	return syserror.ENODEV
-}
-
 // PRead implements vfs.FileDescriptionImpl.PRead.
 func (s *socketVFS2) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	return 0, syserror.ESPIPE
diff --git a/pkg/sentry/socket/unix/socket_refs.go b/pkg/sentry/socket/unix/socket_refs.go
index 680ea06cd..a0e5d1393 100644
--- a/pkg/sentry/socket/unix/socket_refs.go
+++ b/pkg/sentry/socket/unix/socket_refs.go
@@ -1,12 +1,12 @@
 package unix
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/socket/unix/transport/queue_refs.go b/pkg/sentry/socket/unix/transport/queue_refs.go
index 17951eb2f..21d43fc24 100644
--- a/pkg/sentry/socket/unix/transport/queue_refs.go
+++ b/pkg/sentry/socket/unix/transport/queue_refs.go
@@ -1,12 +1,12 @@
 package transport
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/time/seqatomic_parameters_unsafe.go b/pkg/sentry/time/seqatomic_parameters_unsafe.go
index 2cb001080..88d6b5569 100644
--- a/pkg/sentry/time/seqatomic_parameters_unsafe.go
+++ b/pkg/sentry/time/seqatomic_parameters_unsafe.go
@@ -2,11 +2,10 @@ package time
 
 import (
 	"fmt"
+	"gvisor.dev/gvisor/pkg/sync"
 	"reflect"
 	"strings"
 	"unsafe"
-
-	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index 2b29a3c3f..73bb36d3e 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -326,6 +326,9 @@ type FileDescriptionImpl interface {
 	// Allocate grows the file to offset + length bytes.
 	// Only mode == 0 is supported currently.
 	//
+	// Allocate should return EISDIR on directories, ESPIPE on pipes, and ENODEV on
+	// other files where it is not supported.
+	//
 	// Preconditions: The FileDescription was opened for writing.
 	Allocate(ctx context.Context, mode, offset, length uint64) error
 
diff --git a/pkg/sentry/vfs/file_description_impl_util.go b/pkg/sentry/vfs/file_description_impl_util.go
index 68b80a951..78da16bac 100644
--- a/pkg/sentry/vfs/file_description_impl_util.go
+++ b/pkg/sentry/vfs/file_description_impl_util.go
@@ -57,7 +57,11 @@ func (FileDescriptionDefaultImpl) StatFS(ctx context.Context) (linux.Statfs, err
 }
 
 // Allocate implements FileDescriptionImpl.Allocate analogously to
-// fallocate called on regular file, directory or FIFO in Linux.
+// fallocate called on an invalid type of file in Linux.
+//
+// Note that directories can rely on this implementation even though they
+// should technically return EISDIR. Allocate should never be called for a
+// directory, because it requires a writable fd.
 func (FileDescriptionDefaultImpl) Allocate(ctx context.Context, mode, offset, length uint64) error {
 	return syserror.ENODEV
 }
diff --git a/pkg/sentry/vfs/file_description_refs.go b/pkg/sentry/vfs/file_description_refs.go
index 5e612d7f0..ebc089b4c 100644
--- a/pkg/sentry/vfs/file_description_refs.go
+++ b/pkg/sentry/vfs/file_description_refs.go
@@ -1,12 +1,12 @@
 package vfs
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/vfs/filesystem_refs.go b/pkg/sentry/vfs/filesystem_refs.go
index aaa753c43..32f21c044 100644
--- a/pkg/sentry/vfs/filesystem_refs.go
+++ b/pkg/sentry/vfs/filesystem_refs.go
@@ -1,12 +1,12 @@
 package vfs
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so
diff --git a/pkg/sentry/vfs/mount_namespace_refs.go b/pkg/sentry/vfs/mount_namespace_refs.go
index 56b8d9903..2c920ac41 100644
--- a/pkg/sentry/vfs/mount_namespace_refs.go
+++ b/pkg/sentry/vfs/mount_namespace_refs.go
@@ -1,12 +1,12 @@
 package vfs
 
 import (
-	"fmt"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-	"runtime"
 	"sync/atomic"
 
+	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
 )
 
 // ownerType is used to customize logging. Note that we use a pointer to T so