Implement POSIX locks

- Change FileDescriptionImpl Lock/UnlockPOSIX signature to
  take {start,length,whence}, so the correct offset can be
  calculated in the implementations.
- Create PosixLocker interface to make it possible to share
  the same locking code from different implementations.

Closes #1480

PiperOrigin-RevId: 316910286

1 files changed, 38 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/vfs2/fd.go b/pkg/sentry/syscalls/linux/vfs2/fd.go
index f9ccb303c..f5eaa076b 100644
--- a/pkg/sentry/syscalls/linux/vfs2/fd.go
+++ b/pkg/sentry/syscalls/linux/vfs2/fd.go
@@ -17,10 +17,12 @@ package vfs2
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/pipe"
 	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -167,8 +169,44 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		}
 		err := tmpfs.AddSeals(file, args[2].Uint())
 		return 0, nil, err
+	case linux.F_SETLK, linux.F_SETLKW:
+		return 0, nil, posixLock(t, args, file, cmd)
 	default:
 		// TODO(gvisor.dev/issue/2920): Everything else is not yet supported.
 		return 0, nil, syserror.EINVAL
 	}
 }
+
+func posixLock(t *kernel.Task, args arch.SyscallArguments, file *vfs.FileDescription, cmd int32) error {
+	// Copy in the lock request.
+	flockAddr := args[2].Pointer()
+	var flock linux.Flock
+	if _, err := t.CopyIn(flockAddr, &flock); err != nil {
+		return err
+	}
+
+	var blocker lock.Blocker
+	if cmd == linux.F_SETLKW {
+		blocker = t
+	}
+
+	switch flock.Type {
+	case linux.F_RDLCK:
+		if !file.IsReadable() {
+			return syserror.EBADF
+		}
+		return file.LockPOSIX(t, t.FDTable(), lock.ReadLock, uint64(flock.Start), uint64(flock.Len), flock.Whence, blocker)
+
+	case linux.F_WRLCK:
+		if !file.IsWritable() {
+			return syserror.EBADF
+		}
+		return file.LockPOSIX(t, t.FDTable(), lock.WriteLock, uint64(flock.Start), uint64(flock.Len), flock.Whence, blocker)
+
+	case linux.F_UNLCK:
+		return file.UnlockPOSIX(t, t.FDTable(), uint64(flock.Start), uint64(flock.Len), flock.Whence)
+
+	default:
+		return syserror.EINVAL
+	}
+}