Implement F_GETLK fcntl.

Fixes #5113.

PiperOrigin-RevId: 353313374

3 files changed, 37 insertions, 40 deletions

diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index dbf8425b4..eb6c2e36b 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -448,16 +448,19 @@ type FileDescriptionImpl interface {
 	RemoveXattr(ctx context.Context, name string) error
 
 	// LockBSD tries to acquire a BSD-style advisory file lock.
-	LockBSD(ctx context.Context, uid lock.UniqueID, t lock.LockType, block lock.Blocker) error
+	LockBSD(ctx context.Context, uid lock.UniqueID, ownerPID int32, t lock.LockType, block lock.Blocker) error
 
 	// UnlockBSD releases a BSD-style advisory file lock.
 	UnlockBSD(ctx context.Context, uid lock.UniqueID) error
 
 	// LockPOSIX tries to acquire a POSIX-style advisory file lock.
-	LockPOSIX(ctx context.Context, uid lock.UniqueID, t lock.LockType, r lock.LockRange, block lock.Blocker) error
+	LockPOSIX(ctx context.Context, uid lock.UniqueID, ownerPID int32, t lock.LockType, r lock.LockRange, block lock.Blocker) error
 
 	// UnlockPOSIX releases a POSIX-style advisory file lock.
 	UnlockPOSIX(ctx context.Context, uid lock.UniqueID, ComputeLockRange lock.LockRange) error
+
+	// TestPOSIX returns information about whether the specified lock can be held, in the style of the F_GETLK fcntl.
+	TestPOSIX(ctx context.Context, uid lock.UniqueID, t lock.LockType, r lock.LockRange) (linux.Flock, error)
 }
 
 // Dirent holds the information contained in struct linux_dirent64.
@@ -791,9 +794,9 @@ func (fd *FileDescription) Msync(ctx context.Context, mr memmap.MappableRange) e
 }
 
 // LockBSD tries to acquire a BSD-style advisory file lock.
-func (fd *FileDescription) LockBSD(ctx context.Context, lockType lock.LockType, blocker lock.Blocker) error {
+func (fd *FileDescription) LockBSD(ctx context.Context, ownerPID int32, lockType lock.LockType, blocker lock.Blocker) error {
 	atomic.StoreUint32(&fd.usedLockBSD, 1)
-	return fd.impl.LockBSD(ctx, fd, lockType, blocker)
+	return fd.impl.LockBSD(ctx, fd, ownerPID, lockType, blocker)
 }
 
 // UnlockBSD releases a BSD-style advisory file lock.
@@ -802,8 +805,8 @@ func (fd *FileDescription) UnlockBSD(ctx context.Context) error {
 }
 
 // LockPOSIX locks a POSIX-style file range lock.
-func (fd *FileDescription) LockPOSIX(ctx context.Context, uid lock.UniqueID, t lock.LockType, r lock.LockRange, block lock.Blocker) error {
-	return fd.impl.LockPOSIX(ctx, uid, t, r, block)
+func (fd *FileDescription) LockPOSIX(ctx context.Context, uid lock.UniqueID, ownerPID int32, t lock.LockType, r lock.LockRange, block lock.Blocker) error {
+	return fd.impl.LockPOSIX(ctx, uid, ownerPID, t, r, block)
 }
 
 // UnlockPOSIX unlocks a POSIX-style file range lock.
@@ -811,6 +814,11 @@ func (fd *FileDescription) UnlockPOSIX(ctx context.Context, uid lock.UniqueID, r
 	return fd.impl.UnlockPOSIX(ctx, uid, r)
 }
 
+// TestPOSIX returns information about whether the specified lock can be held.
+func (fd *FileDescription) TestPOSIX(ctx context.Context, uid lock.UniqueID, t lock.LockType, r lock.LockRange) (linux.Flock, error) {
+	return fd.impl.TestPOSIX(ctx, uid, t, r)
+}
+
 // ComputeLockRange computes the range of a file lock based on the given values.
 func (fd *FileDescription) ComputeLockRange(ctx context.Context, start uint64, length uint64, whence int16) (lock.LockRange, error) {
 	var off int64
diff --git a/pkg/sentry/vfs/file_description_impl_util.go b/pkg/sentry/vfs/file_description_impl_util.go
index 9d13e2ccb..eb7d2fd3b 100644
--- a/pkg/sentry/vfs/file_description_impl_util.go
+++ b/pkg/sentry/vfs/file_description_impl_util.go
@@ -419,8 +419,8 @@ func (fd *LockFD) Locks() *FileLocks {
 }
 
 // LockBSD implements vfs.FileDescriptionImpl.LockBSD.
-func (fd *LockFD) LockBSD(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, block fslock.Blocker) error {
-	return fd.locks.LockBSD(uid, t, block)
+func (fd *LockFD) LockBSD(ctx context.Context, uid fslock.UniqueID, ownerPID int32, t fslock.LockType, block fslock.Blocker) error {
+	return fd.locks.LockBSD(ctx, uid, ownerPID, t, block)
 }
 
 // UnlockBSD implements vfs.FileDescriptionImpl.UnlockBSD.
@@ -430,8 +430,8 @@ func (fd *LockFD) UnlockBSD(ctx context.Context, uid fslock.UniqueID) error {
 }
 
 // LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
-func (fd *LockFD) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, r fslock.LockRange, block fslock.Blocker) error {
-	return fd.locks.LockPOSIX(ctx, uid, t, r, block)
+func (fd *LockFD) LockPOSIX(ctx context.Context, uid fslock.UniqueID, ownerPID int32, t fslock.LockType, r fslock.LockRange, block fslock.Blocker) error {
+	return fd.locks.LockPOSIX(ctx, uid, ownerPID, t, r, block)
 }
 
 // UnlockPOSIX implements vfs.FileDescriptionImpl.UnlockPOSIX.
@@ -439,6 +439,11 @@ func (fd *LockFD) UnlockPOSIX(ctx context.Context, uid fslock.UniqueID, r fslock
 	return fd.locks.UnlockPOSIX(ctx, uid, r)
 }
 
+// TestPOSIX implements vfs.FileDescriptionImpl.TestPOSIX.
+func (fd *LockFD) TestPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, r fslock.LockRange) (linux.Flock, error) {
+	return fd.locks.TestPOSIX(ctx, uid, t, r)
+}
+
 // NoLockFD implements Lock*/Unlock* portion of FileDescriptionImpl interface
 // returning ENOLCK.
 //
@@ -446,7 +451,7 @@ func (fd *LockFD) UnlockPOSIX(ctx context.Context, uid fslock.UniqueID, r fslock
 type NoLockFD struct{}
 
 // LockBSD implements vfs.FileDescriptionImpl.LockBSD.
-func (NoLockFD) LockBSD(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, block fslock.Blocker) error {
+func (NoLockFD) LockBSD(ctx context.Context, uid fslock.UniqueID, ownerPID int32, t fslock.LockType, block fslock.Blocker) error {
 	return syserror.ENOLCK
 }
 
@@ -456,7 +461,7 @@ func (NoLockFD) UnlockBSD(ctx context.Context, uid fslock.UniqueID) error {
 }
 
 // LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX.
-func (NoLockFD) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, r fslock.LockRange, block fslock.Blocker) error {
+func (NoLockFD) LockPOSIX(ctx context.Context, uid fslock.UniqueID, ownerPID int32, t fslock.LockType, r fslock.LockRange, block fslock.Blocker) error {
 	return syserror.ENOLCK
 }
 
@@ -464,3 +469,8 @@ func (NoLockFD) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.Loc
 func (NoLockFD) UnlockPOSIX(ctx context.Context, uid fslock.UniqueID, r fslock.LockRange) error {
 	return syserror.ENOLCK
 }
+
+// TestPOSIX implements vfs.FileDescriptionImpl.TestPOSIX.
+func (NoLockFD) TestPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, r fslock.LockRange) (linux.Flock, error) {
+	return linux.Flock{}, syserror.ENOLCK
+}
diff --git a/pkg/sentry/vfs/lock.go b/pkg/sentry/vfs/lock.go
index bcff35792..cbe4d8c2d 100644
--- a/pkg/sentry/vfs/lock.go
+++ b/pkg/sentry/vfs/lock.go
@@ -39,8 +39,8 @@ type FileLocks struct {
 }
 
 // LockBSD tries to acquire a BSD-style lock on the entire file.
-func (fl *FileLocks) LockBSD(uid fslock.UniqueID, t fslock.LockType, block fslock.Blocker) error {
-	if fl.bsd.LockRegion(uid, t, fslock.LockRange{0, fslock.LockEOF}, block) {
+func (fl *FileLocks) LockBSD(ctx context.Context, uid fslock.UniqueID, ownerID int32, t fslock.LockType, block fslock.Blocker) error {
+	if fl.bsd.LockRegion(uid, ownerID, t, fslock.LockRange{0, fslock.LockEOF}, block) {
 		return nil
 	}
 
@@ -61,8 +61,8 @@ func (fl *FileLocks) UnlockBSD(uid fslock.UniqueID) {
 }
 
 // LockPOSIX tries to acquire a POSIX-style lock on a file region.
-func (fl *FileLocks) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, r fslock.LockRange, block fslock.Blocker) error {
-	if fl.posix.LockRegion(uid, t, r, block) {
+func (fl *FileLocks) LockPOSIX(ctx context.Context, uid fslock.UniqueID, ownerPID int32, t fslock.LockType, r fslock.LockRange, block fslock.Blocker) error {
+	if fl.posix.LockRegion(uid, ownerPID, t, r, block) {
 		return nil
 	}
 
@@ -83,28 +83,7 @@ func (fl *FileLocks) UnlockPOSIX(ctx context.Context, uid fslock.UniqueID, r fsl
 	return nil
 }
 
-func computeRange(ctx context.Context, fd *FileDescription, start uint64, length uint64, whence int16) (fslock.LockRange, error) {
-	var off int64
-	switch whence {
-	case linux.SEEK_SET:
-		off = 0
-	case linux.SEEK_CUR:
-		// Note that Linux does not hold any mutexes while retrieving the file
-		// offset, see fs/locks.c:flock_to_posix_lock and fs/locks.c:fcntl_setlk.
-		curOff, err := fd.Seek(ctx, 0, linux.SEEK_CUR)
-		if err != nil {
-			return fslock.LockRange{}, err
-		}
-		off = curOff
-	case linux.SEEK_END:
-		stat, err := fd.Stat(ctx, StatOptions{Mask: linux.STATX_SIZE})
-		if err != nil {
-			return fslock.LockRange{}, err
-		}
-		off = int64(stat.Size)
-	default:
-		return fslock.LockRange{}, syserror.EINVAL
-	}
-
-	return fslock.ComputeRange(int64(start), int64(length), off)
+// TestPOSIX returns information about whether the specified lock can be held, in the style of the F_GETLK fcntl.
+func (fl *FileLocks) TestPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, r fslock.LockRange) (linux.Flock, error) {
+	return fl.posix.TestRegion(ctx, uid, t, r), nil
 }