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

5 files changed, 28 insertions, 11 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD
index ef34cb28a..0299dbde9 100644
--- a/pkg/sentry/fsimpl/kernfs/BUILD
+++ b/pkg/sentry/fsimpl/kernfs/BUILD
@@ -49,6 +49,7 @@ go_library(
         "//pkg/sentry/memmap",
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/vfs",
+        "//pkg/sentry/vfs/lock",
         "//pkg/sync",
         "//pkg/syserror",
         "//pkg/usermem",
@@ -67,6 +68,7 @@ go_test(
         "//pkg/sentry/fsimpl/testutil",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/vfs",
+        "//pkg/sentry/vfs/lock",
         "//pkg/syserror",
         "//pkg/usermem",
         "@com_github_google_go-cmp//cmp:go_default_library",
diff --git a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
index 1568a9d49..6418de0a3 100644
--- a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
+++ b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
@@ -21,6 +21,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -38,7 +39,8 @@ type DynamicBytesFile struct {
 	InodeNotDirectory
 	InodeNotSymlink
 
-	data vfs.DynamicBytesSource
+	locks lock.FileLocks
+	data  vfs.DynamicBytesSource
 }
 
 var _ Inode = (*DynamicBytesFile)(nil)
@@ -55,7 +57,7 @@ func (f *DynamicBytesFile) Init(creds *auth.Credentials, devMajor, devMinor uint
 // Open implements Inode.Open.
 func (f *DynamicBytesFile) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
 	fd := &DynamicBytesFD{}
-	if err := fd.Init(rp.Mount(), vfsd, f.data, opts.Flags); err != nil {
+	if err := fd.Init(rp.Mount(), vfsd, f.data, &f.locks, opts.Flags); err != nil {
 		return nil, err
 	}
 	return &fd.vfsfd, nil
@@ -77,13 +79,15 @@ func (*DynamicBytesFile) SetStat(context.Context, *vfs.Filesystem, *auth.Credent
 type DynamicBytesFD struct {
 	vfs.FileDescriptionDefaultImpl
 	vfs.DynamicBytesFileDescriptionImpl
+	vfs.LockFD
 
 	vfsfd vfs.FileDescription
 	inode Inode
 }
 
 // Init initializes a DynamicBytesFD.
-func (fd *DynamicBytesFD) Init(m *vfs.Mount, d *vfs.Dentry, data vfs.DynamicBytesSource, flags uint32) error {
+func (fd *DynamicBytesFD) Init(m *vfs.Mount, d *vfs.Dentry, data vfs.DynamicBytesSource, locks *lock.FileLocks, flags uint32) error {
+	fd.LockFD.Init(locks)
 	if err := fd.vfsfd.Init(fd, flags, m, d, &vfs.FileDescriptionOptions{}); err != nil {
 		return err
 	}
diff --git a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
index 8284e76a7..33a5968ca 100644
--- a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"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"
@@ -42,6 +43,7 @@ import (
 type GenericDirectoryFD struct {
 	vfs.FileDescriptionDefaultImpl
 	vfs.DirectoryFileDescriptionDefaultImpl
+	vfs.LockFD
 
 	vfsfd    vfs.FileDescription
 	children *OrderedChildren
@@ -55,9 +57,9 @@ type GenericDirectoryFD struct {
 
 // NewGenericDirectoryFD creates a new GenericDirectoryFD and returns its
 // dentry.
-func NewGenericDirectoryFD(m *vfs.Mount, d *vfs.Dentry, children *OrderedChildren, opts *vfs.OpenOptions) (*GenericDirectoryFD, error) {
+func NewGenericDirectoryFD(m *vfs.Mount, d *vfs.Dentry, children *OrderedChildren, locks *lock.FileLocks, opts *vfs.OpenOptions) (*GenericDirectoryFD, error) {
 	fd := &GenericDirectoryFD{}
-	if err := fd.Init(children, opts); err != nil {
+	if err := fd.Init(children, locks, opts); err != nil {
 		return nil, err
 	}
 	if err := fd.vfsfd.Init(fd, opts.Flags, m, d, &vfs.FileDescriptionOptions{}); err != nil {
@@ -69,11 +71,12 @@ func NewGenericDirectoryFD(m *vfs.Mount, d *vfs.Dentry, children *OrderedChildre
 // Init initializes a GenericDirectoryFD. Use it when overriding
 // GenericDirectoryFD. Caller must call fd.VFSFileDescription.Init() with the
 // correct implementation.
-func (fd *GenericDirectoryFD) Init(children *OrderedChildren, opts *vfs.OpenOptions) error {
+func (fd *GenericDirectoryFD) Init(children *OrderedChildren, locks *lock.FileLocks, opts *vfs.OpenOptions) error {
 	if vfs.AccessTypesForOpenFlags(opts)&vfs.MayWrite != 0 {
 		// Can't open directories for writing.
 		return syserror.EISDIR
 	}
+	fd.LockFD.Init(locks)
 	fd.children = children
 	return nil
 }
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 982daa2e6..0e4927215 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -555,6 +556,8 @@ type StaticDirectory struct {
 	InodeAttrs
 	InodeNoDynamicLookup
 	OrderedChildren
+
+	locks lock.FileLocks
 }
 
 var _ Inode = (*StaticDirectory)(nil)
@@ -584,7 +587,7 @@ func (s *StaticDirectory) Init(creds *auth.Credentials, devMajor, devMinor uint3
 
 // Open implements kernfs.Inode.
 func (s *StaticDirectory) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := NewGenericDirectoryFD(rp.Mount(), vfsd, &s.OrderedChildren, &opts)
+	fd, err := NewGenericDirectoryFD(rp.Mount(), vfsd, &s.OrderedChildren, &s.locks, &opts)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index 412cf6ac9..6749facf7 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -27,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/testutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -100,8 +101,10 @@ type readonlyDir struct {
 	kernfs.InodeNotSymlink
 	kernfs.InodeNoDynamicLookup
 	kernfs.InodeDirectoryNoNewChildren
-
 	kernfs.OrderedChildren
+
+	locks lock.FileLocks
+
 	dentry kernfs.Dentry
 }
 
@@ -117,7 +120,7 @@ func (fs *filesystem) newReadonlyDir(creds *auth.Credentials, mode linux.FileMod
 }
 
 func (d *readonlyDir) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &d.OrderedChildren, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &d.OrderedChildren, &d.locks, &opts)
 	if err != nil {
 		return nil, err
 	}
@@ -128,10 +131,12 @@ type dir struct {
 	attrs
 	kernfs.InodeNotSymlink
 	kernfs.InodeNoDynamicLookup
+	kernfs.OrderedChildren
+
+	locks lock.FileLocks
 
 	fs     *filesystem
 	dentry kernfs.Dentry
-	kernfs.OrderedChildren
 }
 
 func (fs *filesystem) newDir(creds *auth.Credentials, mode linux.FileMode, contents map[string]*kernfs.Dentry) *kernfs.Dentry {
@@ -147,7 +152,7 @@ func (fs *filesystem) newDir(creds *auth.Credentials, mode linux.FileMode, conte
 }
 
 func (d *dir) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &d.OrderedChildren, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &d.OrderedChildren, &d.locks, &opts)
 	if err != nil {
 		return nil, err
 	}