Implement POSIX locks

- Change FileDescriptionImpl Lock/UnlockPOSIX signature to
  take {start,length,whence}, so the correct offset can be
  calculated in the implementations.
- Create PosixLocker interface to make it possible to share
  the same locking code from different implementations.

Closes #1480

PiperOrigin-RevId: 316910286

3 files changed, 24 insertions, 25 deletions

diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index 062321cbc..e73732a6b 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -62,7 +62,6 @@ go_library(
         "//pkg/sentry/uniqueid",
         "//pkg/sentry/usage",
         "//pkg/sentry/vfs",
-        "//pkg/sentry/vfs/lock",
         "//pkg/sentry/vfs/memxattr",
         "//pkg/sync",
         "//pkg/syserror",
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
index 64e1c40ad..146c7fdfe 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
@@ -138,48 +138,37 @@ func TestLocks(t *testing.T) {
 	}
 	defer cleanup()
 
-	var (
-		uid1 lock.UniqueID
-		uid2 lock.UniqueID
-		// Non-blocking.
-		block lock.Blocker
-	)
-
-	uid1 = 123
-	uid2 = 456
-
-	if err := fd.Impl().LockBSD(ctx, uid1, lock.ReadLock, block); err != nil {
+	uid1 := 123
+	uid2 := 456
+	if err := fd.Impl().LockBSD(ctx, uid1, lock.ReadLock, nil); err != nil {
 		t.Fatalf("fd.Impl().LockBSD failed: err = %v", err)
 	}
-	if err := fd.Impl().LockBSD(ctx, uid2, lock.ReadLock, block); err != nil {
+	if err := fd.Impl().LockBSD(ctx, uid2, lock.ReadLock, nil); err != nil {
 		t.Fatalf("fd.Impl().LockBSD failed: err = %v", err)
 	}
-	if got, want := fd.Impl().LockBSD(ctx, uid2, lock.WriteLock, block), syserror.ErrWouldBlock; got != want {
+	if got, want := fd.Impl().LockBSD(ctx, uid2, lock.WriteLock, nil), syserror.ErrWouldBlock; got != want {
 		t.Fatalf("fd.Impl().LockBSD failed: got = %v, want = %v", got, want)
 	}
 	if err := fd.Impl().UnlockBSD(ctx, uid1); err != nil {
 		t.Fatalf("fd.Impl().UnlockBSD failed: err = %v", err)
 	}
-	if err := fd.Impl().LockBSD(ctx, uid2, lock.WriteLock, block); err != nil {
+	if err := fd.Impl().LockBSD(ctx, uid2, lock.WriteLock, nil); err != nil {
 		t.Fatalf("fd.Impl().LockBSD failed: err = %v", err)
 	}
 
-	rng1 := lock.LockRange{0, 1}
-	rng2 := lock.LockRange{1, 2}
-
-	if err := fd.Impl().LockPOSIX(ctx, uid1, lock.ReadLock, rng1, block); err != nil {
+	if err := fd.Impl().LockPOSIX(ctx, uid1, lock.ReadLock, 0, 1, linux.SEEK_SET, nil); err != nil {
 		t.Fatalf("fd.Impl().LockPOSIX failed: err = %v", err)
 	}
-	if err := fd.Impl().LockPOSIX(ctx, uid2, lock.ReadLock, rng2, block); err != nil {
+	if err := fd.Impl().LockPOSIX(ctx, uid2, lock.ReadLock, 1, 2, linux.SEEK_SET, nil); err != nil {
 		t.Fatalf("fd.Impl().LockPOSIX failed: err = %v", err)
 	}
-	if err := fd.Impl().LockPOSIX(ctx, uid1, lock.WriteLock, rng1, block); err != nil {
+	if err := fd.Impl().LockPOSIX(ctx, uid1, lock.WriteLock, 0, 1, linux.SEEK_SET, nil); err != nil {
 		t.Fatalf("fd.Impl().LockPOSIX failed: err = %v", err)
 	}
-	if got, want := fd.Impl().LockPOSIX(ctx, uid2, lock.ReadLock, rng1, block), syserror.ErrWouldBlock; got != want {
+	if got, want := fd.Impl().LockPOSIX(ctx, uid2, lock.ReadLock, 0, 1, linux.SEEK_SET, nil), syserror.ErrWouldBlock; got != want {
 		t.Fatalf("fd.Impl().LockPOSIX failed: got = %v, want = %v", got, want)
 	}
-	if err := fd.Impl().UnlockPOSIX(ctx, uid1, rng1); err != nil {
+	if err := fd.Impl().UnlockPOSIX(ctx, uid1, 0, 1, linux.SEEK_SET); err != nil {
 		t.Fatalf("fd.Impl().UnlockPOSIX failed: err = %v", err)
 	}
 }
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 71a7522af..d0a3e1a5c 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -36,11 +36,11 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
-	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/vfs/memxattr"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -310,7 +310,7 @@ type inode struct {
 	ctime int64 // nanoseconds
 	mtime int64 // nanoseconds
 
-	locks lock.FileLocks
+	locks vfs.FileLocks
 
 	// Inotify watches for this inode.
 	watches vfs.Watches
@@ -761,9 +761,20 @@ func NewMemfd(mount *vfs.Mount, creds *auth.Credentials, allowSeals bool, name s
 	// Per Linux, mm/shmem.c:__shmem_file_setup(), memfd files are set up with
 	// FMODE_READ | FMODE_WRITE.
 	var fd regularFileFD
+	fd.Init(&inode.locks)
 	flags := uint32(linux.O_RDWR)
 	if err := fd.vfsfd.Init(&fd, flags, mount, &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
 		return nil, err
 	}
 	return &fd.vfsfd, nil
 }
+
+// LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
+func (fd *fileDescription) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, start, length uint64, whence int16, block fslock.Blocker) error {
+	return fd.Locks().LockPOSIX(ctx, &fd.vfsfd, uid, t, start, length, whence, block)
+}
+
+// UnlockPOSIX implements vfs.FileDescriptionImpl.UnlockPOSIX.
+func (fd *fileDescription) UnlockPOSIX(ctx context.Context, uid fslock.UniqueID, start, length uint64, whence int16) error {
+	return fd.Locks().UnlockPOSIX(ctx, &fd.vfsfd, uid, start, length, whence)
+}