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

6 files changed, 23 insertions, 10 deletions

diff --git a/pkg/sentry/fsimpl/proc/BUILD b/pkg/sentry/fsimpl/proc/BUILD
index 17c1342b5..351ba4ee9 100644
--- a/pkg/sentry/fsimpl/proc/BUILD
+++ b/pkg/sentry/fsimpl/proc/BUILD
@@ -35,6 +35,7 @@ go_library(
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/sentry/vfs",
+        "//pkg/sentry/vfs/lock",
         "//pkg/syserror",
         "//pkg/tcpip/header",
         "//pkg/usermem",
diff --git a/pkg/sentry/fsimpl/proc/subtasks.go b/pkg/sentry/fsimpl/proc/subtasks.go
index 36a911db4..e2cdb7ee9 100644
--- a/pkg/sentry/fsimpl/proc/subtasks.go
+++ b/pkg/sentry/fsimpl/proc/subtasks.go
@@ -24,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"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"
 )
 
@@ -37,6 +38,8 @@ type subtasksInode struct {
 	kernfs.OrderedChildren
 	kernfs.AlwaysValid
 
+	locks lock.FileLocks
+
 	fs                *filesystem
 	task              *kernel.Task
 	pidns             *kernel.PIDNamespace
@@ -153,7 +156,7 @@ func (fd *subtasksFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) erro
 // Open implements kernfs.Inode.
 func (i *subtasksInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
 	fd := &subtasksFD{task: i.task}
-	if err := fd.Init(&i.OrderedChildren, &opts); err != nil {
+	if err := fd.Init(&i.OrderedChildren, &i.locks, &opts); err != nil {
 		return nil, err
 	}
 	if err := fd.VFSFileDescription().Init(fd, opts.Flags, rp.Mount(), vfsd, &vfs.FileDescriptionOptions{}); err != nil {
diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index 482055db1..44078a765 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -25,6 +25,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -38,6 +39,8 @@ type taskInode struct {
 	kernfs.InodeAttrs
 	kernfs.OrderedChildren
 
+	locks lock.FileLocks
+
 	task *kernel.Task
 }
 
@@ -103,7 +106,7 @@ func (i *taskInode) Valid(ctx context.Context) bool {
 
 // Open implements kernfs.Inode.
 func (i *taskInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/sentry/fsimpl/proc/task_fds.go b/pkg/sentry/fsimpl/proc/task_fds.go
index 44ccc9e4a..ef6c1d04f 100644
--- a/pkg/sentry/fsimpl/proc/task_fds.go
+++ b/pkg/sentry/fsimpl/proc/task_fds.go
@@ -27,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"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"
 )
 
@@ -53,6 +54,8 @@ func taskFDExists(t *kernel.Task, fd int32) bool {
 }
 
 type fdDir struct {
+	locks lock.FileLocks
+
 	fs   *filesystem
 	task *kernel.Task
 
@@ -143,7 +146,7 @@ func (i *fdDirInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, erro
 
 // Open implements kernfs.Inode.
 func (i *fdDirInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts)
 	if err != nil {
 		return nil, err
 	}
@@ -270,7 +273,7 @@ func (i *fdInfoDirInode) Lookup(ctx context.Context, name string) (*vfs.Dentry,
 
 // Open implements kernfs.Inode.
 func (i *fdInfoDirInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index 2f297e48a..e5eaa91cd 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -30,6 +30,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/mm"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -775,6 +776,8 @@ type namespaceInode struct {
 	kernfs.InodeNoopRefCount
 	kernfs.InodeNotDirectory
 	kernfs.InodeNotSymlink
+
+	locks lock.FileLocks
 }
 
 var _ kernfs.Inode = (*namespaceInode)(nil)
@@ -791,6 +794,7 @@ func (i *namespaceInode) Init(creds *auth.Credentials, devMajor, devMinor uint32
 func (i *namespaceInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
 	fd := &namespaceFD{inode: i}
 	i.IncRef()
+	fd.LockFD.Init(&i.locks)
 	if err := fd.vfsfd.Init(fd, opts.Flags, rp.Mount(), vfsd, &vfs.FileDescriptionOptions{}); err != nil {
 		return nil, err
 	}
@@ -801,6 +805,7 @@ func (i *namespaceInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *
 // /proc/[pid]/ns/*.
 type namespaceFD struct {
 	vfs.FileDescriptionDefaultImpl
+	vfs.LockFD
 
 	vfsfd vfs.FileDescription
 	inode *namespaceInode
@@ -825,8 +830,3 @@ func (fd *namespaceFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) err
 func (fd *namespaceFD) Release() {
 	fd.inode.DecRef()
 }
-
-// OnClose implements FileDescriptionImpl.
-func (*namespaceFD) OnClose(context.Context) error {
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/proc/tasks.go b/pkg/sentry/fsimpl/proc/tasks.go
index b51d43954..58c8b9d05 100644
--- a/pkg/sentry/fsimpl/proc/tasks.go
+++ b/pkg/sentry/fsimpl/proc/tasks.go
@@ -25,6 +25,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"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"
 )
 
@@ -43,6 +44,8 @@ type tasksInode struct {
 	kernfs.OrderedChildren
 	kernfs.AlwaysValid
 
+	locks lock.FileLocks
+
 	fs    *filesystem
 	pidns *kernel.PIDNamespace
 
@@ -197,7 +200,7 @@ func (i *tasksInode) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback
 
 // Open implements kernfs.Inode.
 func (i *tasksInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts)
 	if err != nil {
 		return nil, err
 	}