vfs1: don't allow to open socket files

open() has to return ENXIO in this case.

O_PATH isn't supported by vfs1.

PiperOrigin-RevId: 348820478

pkg/sentry/fs/gofer/inode.go

@@ -475,6 +475,9 @@ func (i *inodeOperations) Check(ctx context.Context, inode *fs.Inode, p fs.PermM
 func (i *inodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
 	switch d.Inode.StableAttr.Type {
 	case fs.Socket:
+		if i.session().overrides != nil {
+			return nil, syserror.ENXIO
+		}
 		return i.getFileSocket(ctx, d, flags)
 	case fs.Pipe:
 		return i.getFilePipe(ctx, d, flags)

pkg/sentry/fs/host/inode.go

@@ -276,6 +276,10 @@ func (i *inodeOperations) BoundEndpoint(inode *fs.Inode, path string) transport.
 
 // GetFile implements fs.InodeOperations.GetFile.
 func (i *inodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	if fs.IsSocket(d.Inode.StableAttr) {
+		return nil, syserror.ENXIO
+	}
+
 	return newFile(ctx, d, flags, i), nil
 }
 

pkg/sentry/fs/ramfs/socket.go

@@ -20,6 +20,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
@@ -63,7 +64,7 @@ func (s *Socket) BoundEndpoint(*fs.Inode, string) transport.BoundEndpoint {
 
 // GetFile implements fs.FileOperations.GetFile.
 func (s *Socket) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
-	return fs.NewFile(ctx, dirent, flags, &socketFileOperations{}), nil
+	return nil, syserror.ENXIO
 }
 
 // +stateify savable

pkg/sentry/fs/tmpfs/inode_file.go

@@ -148,6 +148,10 @@ func (*fileInodeOperations) Rename(ctx context.Context, inode *fs.Inode, oldPare
 
 // GetFile implements fs.InodeOperations.GetFile.
 func (f *fileInodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	if fs.IsSocket(d.Inode.StableAttr) {
+		return nil, syserror.ENXIO
+	}
+
 	if flags.Write {
 		fsmetric.TmpfsOpensW.Increment()
 	} else if flags.Read {

pkg/sentry/syscalls/linux/sys_file.go

@@ -175,6 +175,12 @@ func openAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint) (fd uint
 			}
 		}
 
+		file, err := d.Inode.GetFile(t, d, fileFlags)
+		if err != nil {
+			return syserror.ConvertIntr(err, syserror.ERESTARTSYS)
+		}
+		defer file.DecRef(t)
+
 		// Truncate is called when O_TRUNC is specified for any kind of
 		// existing Dirent. Behavior is delegated to the entry's Truncate
 		// implementation.
@@ -184,12 +190,6 @@ func openAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint) (fd uint
 			}
 		}
 
-		file, err := d.Inode.GetFile(t, d, fileFlags)
-		if err != nil {
-			return syserror.ConvertIntr(err, syserror.ERESTARTSYS)
-		}
-		defer file.DecRef(t)
-
 		// Success.
 		newFD, err := t.NewFDFrom(0, file, kernel.FDFlags{
 			CloseOnExec: flags&linux.O_CLOEXEC != 0,

test/syscalls/linux/BUILD

@@ -3324,6 +3324,7 @@ cc_binary(
         ":socket_test_util",
         ":unix_domain_socket_test_util",
         gtest,
+        "//test/util:file_descriptor",
         "//test/util:test_main",
         "//test/util:test_util",
     ],

test/syscalls/linux/socket_unix_unbound_filesystem.cc

@@ -12,12 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <fcntl.h>
 #include <stdio.h>
 #include <sys/un.h>
 
 #include "gtest/gtest.h"
 #include "test/syscalls/linux/socket_test_util.h"
 #include "test/syscalls/linux/unix_domain_socket_test_util.h"
+#include "test/util/file_descriptor.h"
 #include "test/util/test_util.h"
 
 namespace gvisor {
@@ -70,6 +72,20 @@ TEST_P(UnboundFilesystemUnixSocketPairTest, GetSockNameLength) {
             strlen(want_addr.sun_path) + 1 + sizeof(want_addr.sun_family));
 }
 
+TEST_P(UnboundFilesystemUnixSocketPairTest, OpenSocketWithTruncate) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  ASSERT_THAT(bind(sockets->first_fd(), sockets->first_addr(),
+                   sockets->first_addr_size()),
+              SyscallSucceeds());
+
+  const struct sockaddr_un *addr =
+      reinterpret_cast<const struct sockaddr_un *>(sockets->first_addr());
+  EXPECT_THAT(chmod(addr->sun_path, 0777), SyscallSucceeds());
+  EXPECT_THAT(open(addr->sun_path, O_RDONLY | O_TRUNC),
+              SyscallFailsWithErrno(ENXIO));
+}
+
 INSTANTIATE_TEST_SUITE_P(
     AllUnixDomainSockets, UnboundFilesystemUnixSocketPairTest,
     ::testing::ValuesIn(ApplyVec<SocketPairKind>(