Implement flock(2) in VFS2

LockFD is the generic implementation that can be embedded in
FileDescriptionImpl implementations. Unique lock ID is
maintained in vfs.FileDescription and is created on demand.

Updates #1480

PiperOrigin-RevId: 315604825

4 files changed, 34 insertions, 4 deletions

diff --git a/pkg/sentry/fsimpl/gofer/BUILD b/pkg/sentry/fsimpl/gofer/BUILD
index f5f35a3bc..5cdeeaeb5 100644
--- a/pkg/sentry/fsimpl/gofer/BUILD
+++ b/pkg/sentry/fsimpl/gofer/BUILD
@@ -54,6 +54,7 @@ go_library(
         "//pkg/p9",
         "//pkg/safemem",
         "//pkg/sentry/fs/fsutil",
+        "//pkg/sentry/fs/lock",
         "//pkg/sentry/fsimpl/host",
         "//pkg/sentry/hostfd",
         "//pkg/sentry/kernel",
@@ -68,6 +69,7 @@ go_library(
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/sentry/vfs",
+        "//pkg/sentry/vfs/lock",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/unet",
diff --git a/pkg/sentry/fsimpl/gofer/filesystem.go b/pkg/sentry/fsimpl/gofer/filesystem.go
index 36e0e1856..40933b74b 100644
--- a/pkg/sentry/fsimpl/gofer/filesystem.go
+++ b/pkg/sentry/fsimpl/gofer/filesystem.go
@@ -801,6 +801,7 @@ func (d *dentry) openLocked(ctx context.Context, rp *vfs.ResolvingPath, opts *vf
 				return nil, err
 			}
 			fd := &regularFileFD{}
+			fd.LockFD.Init(&d.locks)
 			if err := fd.vfsfd.Init(fd, opts.Flags, mnt, &d.vfsd, &vfs.FileDescriptionOptions{
 				AllowDirectIO: true,
 			}); err != nil {
@@ -826,6 +827,7 @@ func (d *dentry) openLocked(ctx context.Context, rp *vfs.ResolvingPath, opts *vf
 			}
 		}
 		fd := &directoryFD{}
+		fd.LockFD.Init(&d.locks)
 		if err := fd.vfsfd.Init(fd, opts.Flags, mnt, &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
 			return nil, err
 		}
@@ -842,7 +844,7 @@ func (d *dentry) openLocked(ctx context.Context, rp *vfs.ResolvingPath, opts *vf
 		}
 	case linux.S_IFIFO:
 		if d.isSynthetic() {
-			return d.pipe.Open(ctx, mnt, &d.vfsd, opts.Flags)
+			return d.pipe.Open(ctx, mnt, &d.vfsd, opts.Flags, &d.locks)
 		}
 	}
 	return d.openSpecialFileLocked(ctx, mnt, opts)
@@ -902,7 +904,7 @@ retry:
 			return nil, err
 		}
 	}
-	fd, err := newSpecialFileFD(h, mnt, d, opts.Flags)
+	fd, err := newSpecialFileFD(h, mnt, d, &d.locks, opts.Flags)
 	if err != nil {
 		h.close(ctx)
 		return nil, err
@@ -989,6 +991,7 @@ func (d *dentry) createAndOpenChildLocked(ctx context.Context, rp *vfs.Resolving
 	var childVFSFD *vfs.FileDescription
 	if useRegularFileFD {
 		fd := &regularFileFD{}
+		fd.LockFD.Init(&child.locks)
 		if err := fd.vfsfd.Init(fd, opts.Flags, mnt, &child.vfsd, &vfs.FileDescriptionOptions{
 			AllowDirectIO: true,
 		}); err != nil {
@@ -1003,7 +1006,7 @@ func (d *dentry) createAndOpenChildLocked(ctx context.Context, rp *vfs.Resolving
 		if fdobj != nil {
 			h.fd = int32(fdobj.Release())
 		}
-		fd, err := newSpecialFileFD(h, mnt, child, opts.Flags)
+		fd, err := newSpecialFileFD(h, mnt, child, &d.locks, opts.Flags)
 		if err != nil {
 			h.close(ctx)
 			return nil, err
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 3f3bd56f0..0d88a328e 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -45,6 +45,7 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
+	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/pipe"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
@@ -52,6 +53,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/unet"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -662,6 +664,8 @@ type dentry struct {
 	// If this dentry represents a synthetic named pipe, pipe is the pipe
 	// endpoint bound to this file.
 	pipe *pipe.VFSPipe
+
+	locks lock.FileLocks
 }
 
 // dentryAttrMask returns a p9.AttrMask enabling all attributes used by the
@@ -1366,6 +1370,9 @@ func (d *dentry) decLinks() {
 type fileDescription struct {
 	vfsfd vfs.FileDescription
 	vfs.FileDescriptionDefaultImpl
+	vfs.LockFD
+
+	lockLogging sync.Once
 }
 
 func (fd *fileDescription) filesystem() *filesystem {
@@ -1416,3 +1423,19 @@ func (fd *fileDescription) Setxattr(ctx context.Context, opts vfs.SetxattrOption
 func (fd *fileDescription) Removexattr(ctx context.Context, name string) error {
 	return fd.dentry().removexattr(ctx, auth.CredentialsFromContext(ctx), name)
 }
+
+// LockBSD implements vfs.FileDescriptionImpl.LockBSD.
+func (fd *fileDescription) LockBSD(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, block fslock.Blocker) error {
+	fd.lockLogging.Do(func() {
+		log.Infof("File lock using gofer file handled internally.")
+	})
+	return fd.LockFD.LockBSD(ctx, uid, t, block)
+}
+
+// LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
+func (fd *fileDescription) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, rng fslock.LockRange, block fslock.Blocker) error {
+	fd.lockLogging.Do(func() {
+		log.Infof("Range lock using gofer file handled internally.")
+	})
+	return fd.LockFD.LockPOSIX(ctx, uid, t, rng, block)
+}
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index ff6126b87..289efdd25 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/fdnotifier"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 	"gvisor.dev/gvisor/pkg/waiter"
@@ -51,7 +52,7 @@ type specialFileFD struct {
 	off int64
 }
 
-func newSpecialFileFD(h handle, mnt *vfs.Mount, d *dentry, flags uint32) (*specialFileFD, error) {
+func newSpecialFileFD(h handle, mnt *vfs.Mount, d *dentry, locks *lock.FileLocks, flags uint32) (*specialFileFD, error) {
 	ftype := d.fileType()
 	seekable := ftype == linux.S_IFREG
 	mayBlock := ftype == linux.S_IFIFO || ftype == linux.S_IFSOCK
@@ -60,6 +61,7 @@ func newSpecialFileFD(h handle, mnt *vfs.Mount, d *dentry, flags uint32) (*speci
 		seekable: seekable,
 		mayBlock: mayBlock,
 	}
+	fd.LockFD.Init(locks)
 	if mayBlock && h.fd >= 0 {
 		if err := fdnotifier.AddFD(h.fd, &fd.queue); err != nil {
 			return nil, err