Implement file locks for regular tmpfs files in VFSv2.

Add a file lock implementation that can be embedded into various filesystem
implementations.

Updates #1480

PiperOrigin-RevId: 292614758

4 files changed, 125 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index c61366224..57abd5583 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -38,6 +38,7 @@ go_library(
         "//pkg/sentry/arch",
         "//pkg/sentry/fs",
         "//pkg/sentry/fs/fsutil",
+        "//pkg/sentry/fs/lock",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/pipe",
@@ -47,6 +48,7 @@ go_library(
         "//pkg/sentry/platform",
         "//pkg/sentry/usage",
         "//pkg/sentry/vfs",
+        "//pkg/sentry/vfs/lock",
         "//pkg/sync",
         "//pkg/syserror",
         "//pkg/usermem",
@@ -86,6 +88,7 @@ go_test(
         "//pkg/context",
         "//pkg/fspath",
         "//pkg/sentry/contexttest",
+        "//pkg/sentry/fs/lock",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/contexttest",
         "//pkg/sentry/vfs",
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index e9e6faf67..dab346a41 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
@@ -192,6 +193,28 @@ func (fd *regularFileFD) Sync(ctx context.Context) error {
 	return nil
 }
 
+// LockBSD implements vfs.FileDescriptionImpl.LockBSD.
+func (fd *regularFileFD) LockBSD(ctx context.Context, uid lock.UniqueID, t lock.LockType, block lock.Blocker) error {
+	return fd.inode().lockBSD(uid, t, block)
+}
+
+// UnlockBSD implements vfs.FileDescriptionImpl.UnlockBSD.
+func (fd *regularFileFD) UnlockBSD(ctx context.Context, uid lock.UniqueID) error {
+	fd.inode().unlockBSD(uid)
+	return nil
+}
+
+// LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
+func (fd *regularFileFD) LockPOSIX(ctx context.Context, uid lock.UniqueID, t lock.LockType, rng lock.LockRange, block lock.Blocker) error {
+	return fd.inode().lockPOSIX(uid, t, rng, block)
+}
+
+// UnlockPOSIX implements vfs.FileDescriptionImpl.UnlockPOSIX.
+func (fd *regularFileFD) UnlockPOSIX(ctx context.Context, uid lock.UniqueID, rng lock.LockRange) error {
+	fd.inode().unlockPOSIX(uid, rng)
+	return nil
+}
+
 // regularFileReadWriter implements safemem.Reader and Safemem.Writer.
 type regularFileReadWriter struct {
 	file *regularFile
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
index 32552e261..2b52992ea 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
@@ -24,9 +24,11 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
+	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/contexttest"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -260,6 +262,60 @@ func TestPWrite(t *testing.T) {
 	}
 }
 
+func TestLocks(t *testing.T) {
+	ctx := contexttest.Context(t)
+	fd, cleanup, err := newFileFD(ctx, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	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 {
+		t.Fatalf("fd.Impl().LockBSD failed: err = %v", err)
+	}
+	if err := fd.Impl().LockBSD(ctx, uid2, lock.ReadLock, block); 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 {
+		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 {
+		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 {
+		t.Fatalf("fd.Impl().LockPOSIX failed: err = %v", err)
+	}
+	if err := fd.Impl().LockPOSIX(ctx, uid2, lock.ReadLock, rng2, block); err != nil {
+		t.Fatalf("fd.Impl().LockPOSIX failed: err = %v", err)
+	}
+	if err := fd.Impl().LockPOSIX(ctx, uid1, lock.WriteLock, rng1, block); 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 {
+		t.Fatalf("fd.Impl().LockPOSIX failed: got = %v, want = %v", got, want)
+	}
+	if err := fd.Impl().UnlockPOSIX(ctx, uid1, rng1); err != nil {
+		t.Fatalf("fd.Impl().UnlockPOSIX failed: err = %v", err)
+	}
+}
+
 func TestPRead(t *testing.T) {
 	ctx := contexttest.Context(t)
 	fd, cleanup, err := newFileFD(ctx, 0644)
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 88dbd6e35..2108d0f4d 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -30,10 +30,12 @@ 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/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -153,6 +155,9 @@ type inode struct {
 	rdevMajor uint32
 	rdevMinor uint32
 
+	// Advisory file locks, which lock at the inode level.
+	locks lock.FileLocks
+
 	impl interface{} // immutable
 }
 
@@ -352,6 +357,44 @@ func (i *inode) setStat(stat linux.Statx) error {
 	return nil
 }
 
+// TODO(gvisor.dev/issue/1480): support file locking for file types other than regular.
+func (i *inode) lockBSD(uid fslock.UniqueID, t fslock.LockType, block fslock.Blocker) error {
+	switch i.impl.(type) {
+	case *regularFile:
+		return i.locks.LockBSD(uid, t, block)
+	}
+	return syserror.EBADF
+}
+
+// TODO(gvisor.dev/issue/1480): support file locking for file types other than regular.
+func (i *inode) unlockBSD(uid fslock.UniqueID) error {
+	switch i.impl.(type) {
+	case *regularFile:
+		i.locks.UnlockBSD(uid)
+		return nil
+	}
+	return syserror.EBADF
+}
+
+// TODO(gvisor.dev/issue/1480): support file locking for file types other than regular.
+func (i *inode) lockPOSIX(uid fslock.UniqueID, t fslock.LockType, rng fslock.LockRange, block fslock.Blocker) error {
+	switch i.impl.(type) {
+	case *regularFile:
+		return i.locks.LockPOSIX(uid, t, rng, block)
+	}
+	return syserror.EBADF
+}
+
+// TODO(gvisor.dev/issue/1480): support file locking for file types other than regular.
+func (i *inode) unlockPOSIX(uid fslock.UniqueID, rng fslock.LockRange) error {
+	switch i.impl.(type) {
+	case *regularFile:
+		i.locks.UnlockPOSIX(uid, rng)
+		return nil
+	}
+	return syserror.EBADF
+}
+
 // allocatedBlocksForSize returns the number of 512B blocks needed to
 // accommodate the given size in bytes, as appropriate for struct
 // stat::st_blocks and struct statx::stx_blocks. (Note that this 512B block