2 files changed, 13 insertions, 10 deletions
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go
index d5e73ddae..1cd2982cb 100644
--- a/pkg/sentry/fsimpl/host/host.go
+++ b/pkg/sentry/fsimpl/host/host.go
@@ -543,6 +543,16 @@ func (f *fileDescription) Release() {
 	// noop
 }
 
+// Allocate implements vfs.FileDescriptionImpl.
+func (f *fileDescription) Allocate(ctx context.Context, mode, offset, length uint64) error {
+	if !f.inode.seekable {
+		return syserror.ESPIPE
+	}
+
+	// TODO(gvisor.dev/issue/2923): Implement Allocate for non-pipe hostfds.
+	return syserror.EOPNOTSUPP
+}
+
 // PRead implements FileDescriptionImpl.
 func (f *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	i := f.inode
@@ -578,8 +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/host/socket.go b/pkg/sentry/fsimpl/host/socket.go
index 38f1fbfba..fd16bd92d 100644
--- a/pkg/sentry/fsimpl/host/socket.go
+++ b/pkg/sentry/fsimpl/host/socket.go
@@ -47,11 +47,6 @@ func newEndpoint(ctx context.Context, hostFD int, queue *waiter.Queue) (transpor
 	return ep, nil
 }
 
-// maxSendBufferSize is the maximum host send buffer size allowed for endpoint.
-//
-// N.B. 8MB is the default maximum on Linux (2 * sysctl_wmem_max).
-const maxSendBufferSize = 8 << 20
-
 // ConnectedEndpoint is an implementation of transport.ConnectedEndpoint and
 // transport.Receiver. It is backed by a host fd that was imported at sentry
 // startup. This fd is shared with a hostfs inode, which retains ownership of
@@ -114,10 +109,6 @@ func (c *ConnectedEndpoint) init() *syserr.Error {
 	if err != nil {
 		return syserr.FromError(err)
 	}
-	if sndbuf > maxSendBufferSize {
-		log.Warningf("Socket send buffer too large: %d", sndbuf)
-		return syserr.ErrInvalidEndpointState
-	}
 
 	c.stype = linux.SockType(stype)
 	c.sndbuf = int64(sndbuf)