From 8ab0848c70fcebe377a0e7abdebf371022c96830 Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@google.com>
Date: Tue, 18 Jun 2019 01:42:28 -0700
Subject: gvisor/fs: don't update file.offset for sockets, pipes, etc

sockets, pipes and other non-seekable file descriptors don't
use file.offset, so we don't need to update it.

With this change, we will be able to call file operations
without locking the file.mu mutex. This is already used for
pipes in the splice system call.

PiperOrigin-RevId: 253746644
---
 pkg/sentry/socket/epsocket/epsocket.go | 2 +-
 pkg/sentry/socket/hostinet/socket.go   | 2 +-
 pkg/sentry/socket/netlink/provider.go  | 2 +-
 pkg/sentry/socket/rpcinet/socket.go    | 8 +++++++-
 pkg/sentry/socket/unix/unix.go         | 2 +-
 5 files changed, 11 insertions(+), 5 deletions(-)

(limited to 'pkg/sentry/socket')

diff --git a/pkg/sentry/socket/epsocket/epsocket.go b/pkg/sentry/socket/epsocket/epsocket.go
index a42cf4caf..8e65e1b3f 100644
--- a/pkg/sentry/socket/epsocket/epsocket.go
+++ b/pkg/sentry/socket/epsocket/epsocket.go
@@ -262,7 +262,7 @@ func New(t *kernel.Task, family int, skType linux.SockType, protocol int, queue
 
 	dirent := socket.NewDirent(t, epsocketDevice)
 	defer dirent.DecRef()
-	return fs.NewFile(t, dirent, fs.FileFlags{Read: true, Write: true}, &SocketOperations{
+	return fs.NewFile(t, dirent, fs.FileFlags{Read: true, Write: true, NonSeekable: true}, &SocketOperations{
 		Queue:    queue,
 		family:   family,
 		Endpoint: endpoint,
diff --git a/pkg/sentry/socket/hostinet/socket.go b/pkg/sentry/socket/hostinet/socket.go
index cef007aca..c63f3aacf 100644
--- a/pkg/sentry/socket/hostinet/socket.go
+++ b/pkg/sentry/socket/hostinet/socket.go
@@ -77,7 +77,7 @@ func newSocketFile(ctx context.Context, family int, stype linux.SockType, protoc
 	}
 	dirent := socket.NewDirent(ctx, socketDevice)
 	defer dirent.DecRef()
-	return fs.NewFile(ctx, dirent, fs.FileFlags{NonBlocking: nonblock, Read: true, Write: true}, s), nil
+	return fs.NewFile(ctx, dirent, fs.FileFlags{NonBlocking: nonblock, Read: true, Write: true, NonSeekable: true}, s), nil
 }
 
 // Release implements fs.FileOperations.Release.
diff --git a/pkg/sentry/socket/netlink/provider.go b/pkg/sentry/socket/netlink/provider.go
index 31d2ca494..689cad997 100644
--- a/pkg/sentry/socket/netlink/provider.go
+++ b/pkg/sentry/socket/netlink/provider.go
@@ -89,7 +89,7 @@ func (*socketProvider) Socket(t *kernel.Task, stype linux.SockType, protocol int
 
 	d := socket.NewDirent(t, netlinkSocketDevice)
 	defer d.DecRef()
-	return fs.NewFile(t, d, fs.FileFlags{Read: true, Write: true}, s), nil
+	return fs.NewFile(t, d, fs.FileFlags{Read: true, Write: true, NonSeekable: true}, s), nil
 }
 
 // Pair implements socket.Provider.Pair by returning an error.
diff --git a/pkg/sentry/socket/rpcinet/socket.go b/pkg/sentry/socket/rpcinet/socket.go
index ba33eb671..c76b48ead 100644
--- a/pkg/sentry/socket/rpcinet/socket.go
+++ b/pkg/sentry/socket/rpcinet/socket.go
@@ -322,7 +322,13 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 
 	dirent := socket.NewDirent(t, socketDevice)
 	defer dirent.DecRef()
-	file := fs.NewFile(t, dirent, fs.FileFlags{Read: true, Write: true, NonBlocking: flags&linux.SOCK_NONBLOCK != 0}, &socketOperations{
+	fileFlags := fs.FileFlags{
+		Read:        true,
+		Write:       true,
+		NonSeekable: true,
+		NonBlocking: flags&linux.SOCK_NONBLOCK != 0,
+	}
+	file := fs.NewFile(t, dirent, fileFlags, &socketOperations{
 		wq:       &wq,
 		fd:       payload.Fd,
 		rpcConn:  s.rpcConn,
diff --git a/pkg/sentry/socket/unix/unix.go b/pkg/sentry/socket/unix/unix.go
index 97db87f3e..5fc43db8c 100644
--- a/pkg/sentry/socket/unix/unix.go
+++ b/pkg/sentry/socket/unix/unix.go
@@ -64,7 +64,7 @@ type SocketOperations struct {
 func New(ctx context.Context, endpoint transport.Endpoint, stype linux.SockType) *fs.File {
 	dirent := socket.NewDirent(ctx, unixSocketDevice)
 	defer dirent.DecRef()
-	return NewWithDirent(ctx, dirent, endpoint, stype, fs.FileFlags{Read: true, Write: true})
+	return NewWithDirent(ctx, dirent, endpoint, stype, fs.FileFlags{Read: true, Write: true, NonSeekable: true})
 }
 
 // NewWithDirent creates a new unix socket using an existing dirent.
-- 
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