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, 23 insertions, 7 deletions

diff --git a/pkg/sentry/kernel/fd_table.go b/pkg/sentry/kernel/fd_table.go
index 48911240f..4b7d234a4 100644
--- a/pkg/sentry/kernel/fd_table.go
+++ b/pkg/sentry/kernel/fd_table.go
@@ -29,6 +29,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // FDFlags define flags for an individual descriptor.
@@ -148,7 +149,12 @@ func (f *FDTable) drop(file *fs.File) {
 
 // dropVFS2 drops the table reference.
 func (f *FDTable) dropVFS2(file *vfs.FileDescription) {
-	// TODO(gvisor.dev/issue/1480): Release locks.
+	// Release any POSIX lock possibly held by the FDTable. Range {0, 0} means the
+	// entire file.
+	err := file.UnlockPOSIX(context.Background(), f, 0, 0, linux.SEEK_SET)
+	if err != nil && err != syserror.ENOLCK {
+		panic(fmt.Sprintf("UnlockPOSIX failed: %v", err))
+	}
 
 	// Generate inotify events.
 	ev := uint32(linux.IN_CLOSE_NOWRITE)
@@ -157,7 +163,7 @@ func (f *FDTable) dropVFS2(file *vfs.FileDescription) {
 	}
 	file.Dentry().InotifyWithParent(ev, 0, vfs.PathEvent)
 
-	// Drop the table reference.
+	// Drop the table's reference.
 	file.DecRef()
 }
 
diff --git a/pkg/sentry/kernel/pipe/BUILD b/pkg/sentry/kernel/pipe/BUILD
index 0db546b98..449643118 100644
--- a/pkg/sentry/kernel/pipe/BUILD
+++ b/pkg/sentry/kernel/pipe/BUILD
@@ -26,8 +26,8 @@ go_library(
         "//pkg/sentry/device",
         "//pkg/sentry/fs",
         "//pkg/sentry/fs/fsutil",
+        "//pkg/sentry/fs/lock",
         "//pkg/sentry/vfs",
-        "//pkg/sentry/vfs/lock",
         "//pkg/sync",
         "//pkg/syserror",
         "//pkg/usermem",
diff --git a/pkg/sentry/kernel/pipe/vfs.go b/pkg/sentry/kernel/pipe/vfs.go
index c0e9ee1f4..a4519363f 100644
--- a/pkg/sentry/kernel/pipe/vfs.go
+++ b/pkg/sentry/kernel/pipe/vfs.go
@@ -20,8 +20,8 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
-	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -63,12 +63,12 @@ func NewVFSPipe(isNamed bool, sizeBytes, atomicIOBytes int64) *VFSPipe {
 // Preconditions: statusFlags should not contain an open access mode.
 func (vp *VFSPipe) ReaderWriterPair(mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlags uint32) (*vfs.FileDescription, *vfs.FileDescription) {
 	// Connected pipes share the same locks.
-	locks := &lock.FileLocks{}
+	locks := &vfs.FileLocks{}
 	return vp.newFD(mnt, vfsd, linux.O_RDONLY|statusFlags, locks), vp.newFD(mnt, vfsd, linux.O_WRONLY|statusFlags, locks)
 }
 
 // Open opens the pipe represented by vp.
-func (vp *VFSPipe) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlags uint32, locks *lock.FileLocks) (*vfs.FileDescription, error) {
+func (vp *VFSPipe) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlags uint32, locks *vfs.FileLocks) (*vfs.FileDescription, error) {
 	vp.mu.Lock()
 	defer vp.mu.Unlock()
 
@@ -130,7 +130,7 @@ func (vp *VFSPipe) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, s
 }
 
 // Preconditions: vp.mu must be held.
-func (vp *VFSPipe) newFD(mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlags uint32, locks *lock.FileLocks) *vfs.FileDescription {
+func (vp *VFSPipe) newFD(mnt *vfs.Mount, vfsd *vfs.Dentry, statusFlags uint32, locks *vfs.FileLocks) *vfs.FileDescription {
 	fd := &VFSPipeFD{
 		pipe: &vp.pipe,
 	}
@@ -451,3 +451,13 @@ func spliceOrTee(ctx context.Context, dst, src *VFSPipeFD, count int64, removeFr
 	}
 	return n, err
 }
+
+// LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
+func (fd *VFSPipeFD) 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 *VFSPipeFD) UnlockPOSIX(ctx context.Context, uid fslock.UniqueID, start, length uint64, whence int16) error {
+	return fd.Locks().UnlockPOSIX(ctx, &fd.vfsfd, uid, start, length, whence)
+}