Update preadv2/pwritev2 flag handling in vfs2.

We do not support RWF_SYNC/RWF_DSYNC and probably shouldn't silently accept
them, since the user may incorrectly believe that we are synchronizing I/O.
Remove the pwritev2 test verifying that we support these flags.

gvisor.dev/issue/2601 is the tracking bug for deciding which RWF_.* flags
we need and supporting them.

Updates #2923, #2601.

PiperOrigin-RevId: 319351286

4 files changed, 25 insertions, 9 deletions

diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go
index faba73af2..3d2d3530a 100644
--- a/pkg/sentry/fsimpl/gofer/regular_file.go
+++ b/pkg/sentry/fsimpl/gofer/regular_file.go
@@ -102,7 +102,9 @@ func (fd *regularFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offs
 		return 0, syserror.EINVAL
 	}
 
-	// Check that flags are supported. Silently ignore RWF_HIPRI.
+	// Check that flags are supported.
+	//
+	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
 	if opts.Flags&^linux.RWF_HIPRI != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}
@@ -155,7 +157,9 @@ func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off
 		return 0, syserror.EINVAL
 	}
 
-	// Check that flags are supported. Silently ignore RWF_HIPRI.
+	// Check that flags are supported.
+	//
+	// TODO(gvisor.dev/issue/2601): Support select pwritev2 flags.
 	if opts.Flags&^linux.RWF_HIPRI != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index 2b381af05..3c4e7e2e4 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -130,7 +130,9 @@ func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offs
 		return 0, syserror.EINVAL
 	}
 
-	// Check that flags are supported. Silently ignore RWF_HIPRI.
+	// Check that flags are supported.
+	//
+	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
 	if opts.Flags&^linux.RWF_HIPRI != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}
@@ -176,7 +178,9 @@ func (fd *specialFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off
 		return 0, syserror.EINVAL
 	}
 
-	// Check that flags are supported. Silently ignore RWF_HIPRI.
+	// Check that flags are supported.
+	//
+	// TODO(gvisor.dev/issue/2601): Support select pwritev2 flags.
 	if opts.Flags&^linux.RWF_HIPRI != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go
index 007b3332e..1cd2982cb 100644
--- a/pkg/sentry/fsimpl/host/host.go
+++ b/pkg/sentry/fsimpl/host/host.go
@@ -588,8 +588,10 @@ func (f *fileDescription) Read(ctx context.Context, dst usermem.IOSequence, opts
 }
 
 func readFromHostFD(ctx context.Context, hostFD int, dst usermem.IOSequence, offset int64, flags uint32) (int64, error) {
+	// Check that flags are supported.
+	//
 	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
-	if flags != 0 {
+	if flags&^linux.RWF_HIPRI != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}
 	reader := hostfd.GetReadWriterAt(int32(hostFD), offset, flags)
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index 6691add96..1cdb46e6f 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -295,8 +295,11 @@ func (fd *regularFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offs
 		return 0, syserror.EINVAL
 	}
 
-	// Check that flags are supported. Silently ignore RWF_HIPRI.
-	if opts.Flags&^linux.RWF_HIPRI != 0 {
+	// Check that flags are supported. RWF_DSYNC/RWF_SYNC can be ignored since
+	// all state is in-memory.
+	//
+	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
+	if opts.Flags&^(linux.RWF_HIPRI|linux.RWF_DSYNC|linux.RWF_SYNC) != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}
 
@@ -326,8 +329,11 @@ func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off
 		return 0, syserror.EINVAL
 	}
 
-	// Check that flags are supported. Silently ignore RWF_HIPRI.
-	if opts.Flags&^linux.RWF_HIPRI != 0 {
+	// Check that flags are supported. RWF_DSYNC/RWF_SYNC can be ignored since
+	// all state is in-memory.
+	//
+	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
+	if opts.Flags&^(linux.RWF_HIPRI|linux.RWF_DSYNC|linux.RWF_SYNC) != 0 {
 		return 0, syserror.EOPNOTSUPP
 	}