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-rw-r--r--pkg/sentry/vfs/BUILD10
-rw-r--r--pkg/sentry/vfs/file_description_impl_util.go107
-rw-r--r--pkg/sentry/vfs/file_description_impl_util_test.go134
-rw-r--r--pkg/sentry/vfs/testutil.go139
4 files changed, 390 insertions, 0 deletions
diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD
index 4de6c41cf..0f247bf77 100644
--- a/pkg/sentry/vfs/BUILD
+++ b/pkg/sentry/vfs/BUILD
@@ -18,6 +18,7 @@ go_library(
"permissions.go",
"resolving_path.go",
"syscalls.go",
+ "testutil.go",
"vfs.go",
],
importpath = "gvisor.dev/gvisor/pkg/sentry/vfs",
@@ -40,7 +41,16 @@ go_test(
name = "vfs_test",
size = "small",
srcs = [
+ "file_description_impl_util_test.go",
"mount_test.go",
],
embed = [":vfs"],
+ deps = [
+ "//pkg/abi/linux",
+ "//pkg/sentry/context",
+ "//pkg/sentry/context/contexttest",
+ "//pkg/sentry/kernel/auth",
+ "//pkg/sentry/usermem",
+ "//pkg/syserror",
+ ],
)
diff --git a/pkg/sentry/vfs/file_description_impl_util.go b/pkg/sentry/vfs/file_description_impl_util.go
index 486893e70..4d1d447ed 100644
--- a/pkg/sentry/vfs/file_description_impl_util.go
+++ b/pkg/sentry/vfs/file_description_impl_util.go
@@ -15,6 +15,10 @@
package vfs
import (
+ "bytes"
+ "io"
+ "sync"
+
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/context"
@@ -140,3 +144,106 @@ func (DirectoryFileDescriptionDefaultImpl) PWrite(ctx context.Context, src userm
func (DirectoryFileDescriptionDefaultImpl) Write(ctx context.Context, src usermem.IOSequence, opts WriteOptions) (int64, error) {
return 0, syserror.EISDIR
}
+
+// DynamicBytesFileDescriptionImpl may be embedded by implementations of
+// FileDescriptionImpl that represent read-only regular files whose contents
+// are backed by a bytes.Buffer that is regenerated when necessary, consistent
+// with Linux's fs/seq_file.c:single_open().
+//
+// DynamicBytesFileDescriptionImpl.SetDataSource() must be called before first
+// use.
+type DynamicBytesFileDescriptionImpl struct {
+ FileDescriptionDefaultImpl
+
+ data DynamicBytesSource // immutable
+ mu sync.Mutex // protects the following fields
+ buf bytes.Buffer
+ off int64
+ lastRead int64 // offset at which the last Read, PRead, or Seek ended
+}
+
+// DynamicBytesSource represents a data source for a
+// DynamicBytesFileDescriptionImpl.
+type DynamicBytesSource interface {
+ // Generate writes the file's contents to buf.
+ Generate(ctx context.Context, buf *bytes.Buffer) error
+}
+
+// SetDataSource must be called exactly once on fd before first use.
+func (fd *DynamicBytesFileDescriptionImpl) SetDataSource(data DynamicBytesSource) {
+ fd.data = data
+}
+
+// Preconditions: fd.mu must be locked.
+func (fd *DynamicBytesFileDescriptionImpl) preadLocked(ctx context.Context, dst usermem.IOSequence, offset int64, opts *ReadOptions) (int64, error) {
+ // Regenerate the buffer if it's empty, or before pread() at a new offset.
+ // Compare fs/seq_file.c:seq_read() => traverse().
+ switch {
+ case offset != fd.lastRead:
+ fd.buf.Reset()
+ fallthrough
+ case fd.buf.Len() == 0:
+ if err := fd.data.Generate(ctx, &fd.buf); err != nil {
+ fd.buf.Reset()
+ // fd.off is not updated in this case.
+ fd.lastRead = 0
+ return 0, err
+ }
+ }
+ bs := fd.buf.Bytes()
+ if offset >= int64(len(bs)) {
+ return 0, io.EOF
+ }
+ n, err := dst.CopyOut(ctx, bs[offset:])
+ fd.lastRead = offset + int64(n)
+ return int64(n), err
+}
+
+// PRead implements FileDescriptionImpl.PRead.
+func (fd *DynamicBytesFileDescriptionImpl) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts ReadOptions) (int64, error) {
+ fd.mu.Lock()
+ n, err := fd.preadLocked(ctx, dst, offset, &opts)
+ fd.mu.Unlock()
+ return n, err
+}
+
+// Read implements FileDescriptionImpl.Read.
+func (fd *DynamicBytesFileDescriptionImpl) Read(ctx context.Context, dst usermem.IOSequence, opts ReadOptions) (int64, error) {
+ fd.mu.Lock()
+ n, err := fd.preadLocked(ctx, dst, fd.off, &opts)
+ fd.off += n
+ fd.mu.Unlock()
+ return n, err
+}
+
+// Seek implements FileDescriptionImpl.Seek.
+func (fd *DynamicBytesFileDescriptionImpl) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+ fd.mu.Lock()
+ defer fd.mu.Unlock()
+ switch whence {
+ case linux.SEEK_SET:
+ // Use offset as given.
+ case linux.SEEK_CUR:
+ offset += fd.off
+ default:
+ // fs/seq_file:seq_lseek() rejects SEEK_END etc.
+ return 0, syserror.EINVAL
+ }
+ if offset < 0 {
+ return 0, syserror.EINVAL
+ }
+ if offset != fd.lastRead {
+ // Regenerate the file's contents immediately. Compare
+ // fs/seq_file.c:seq_lseek() => traverse().
+ fd.buf.Reset()
+ if err := fd.data.Generate(ctx, &fd.buf); err != nil {
+ fd.buf.Reset()
+ fd.off = 0
+ fd.lastRead = 0
+ return 0, err
+ }
+ fd.lastRead = offset
+ }
+ fd.off = offset
+ return offset, nil
+}
diff --git a/pkg/sentry/vfs/file_description_impl_util_test.go b/pkg/sentry/vfs/file_description_impl_util_test.go
new file mode 100644
index 000000000..cef7e3ce5
--- /dev/null
+++ b/pkg/sentry/vfs/file_description_impl_util_test.go
@@ -0,0 +1,134 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs
+
+import (
+ "bytes"
+ "fmt"
+ "io"
+ "sync/atomic"
+ "testing"
+
+ "gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/sentry/context"
+ "gvisor.dev/gvisor/pkg/sentry/context/contexttest"
+ "gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+ "gvisor.dev/gvisor/pkg/sentry/usermem"
+ "gvisor.dev/gvisor/pkg/syserror"
+)
+
+// genCountFD is a read-only FileDescriptionImpl representing a regular file
+// that contains the number of times its DynamicBytesSource.Generate()
+// implementation has been called.
+type genCountFD struct {
+ vfsfd FileDescription
+ DynamicBytesFileDescriptionImpl
+
+ count uint64 // accessed using atomic memory ops
+}
+
+func newGenCountFD(mnt *Mount, vfsd *Dentry) *FileDescription {
+ var fd genCountFD
+ fd.vfsfd.Init(&fd, mnt, vfsd)
+ fd.DynamicBytesFileDescriptionImpl.SetDataSource(&fd)
+ return &fd.vfsfd
+}
+
+// Release implements FileDescriptionImpl.Release.
+func (fd *genCountFD) Release() {
+}
+
+// StatusFlags implements FileDescriptionImpl.StatusFlags.
+func (fd *genCountFD) StatusFlags(ctx context.Context) (uint32, error) {
+ return 0, nil
+}
+
+// SetStatusFlags implements FileDescriptionImpl.SetStatusFlags.
+func (fd *genCountFD) SetStatusFlags(ctx context.Context, flags uint32) error {
+ return syserror.EPERM
+}
+
+// Stat implements FileDescriptionImpl.Stat.
+func (fd *genCountFD) Stat(ctx context.Context, opts StatOptions) (linux.Statx, error) {
+ // Note that Statx.Mask == 0 in the return value.
+ return linux.Statx{}, nil
+}
+
+// SetStat implements FileDescriptionImpl.SetStat.
+func (fd *genCountFD) SetStat(ctx context.Context, opts SetStatOptions) error {
+ return syserror.EPERM
+}
+
+// Generate implements DynamicBytesSource.Generate.
+func (fd *genCountFD) Generate(ctx context.Context, buf *bytes.Buffer) error {
+ fmt.Fprintf(buf, "%d", atomic.AddUint64(&fd.count, 1))
+ return nil
+}
+
+func TestGenCountFD(t *testing.T) {
+ ctx := contexttest.Context(t)
+ creds := auth.CredentialsFromContext(ctx)
+
+ vfsObj := New() // vfs.New()
+ vfsObj.MustRegisterFilesystemType("testfs", FDTestFilesystemType{})
+ mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "testfs", &NewFilesystemOptions{})
+ if err != nil {
+ t.Fatalf("failed to create testfs root mount: %v", err)
+ }
+ vd := mntns.Root()
+ defer vd.DecRef()
+
+ fd := newGenCountFD(vd.Mount(), vd.Dentry())
+ defer fd.DecRef()
+
+ // The first read causes Generate to be called to fill the FD's buffer.
+ buf := make([]byte, 2)
+ ioseq := usermem.BytesIOSequence(buf)
+ n, err := fd.Impl().Read(ctx, ioseq, ReadOptions{})
+ if n != 1 || (err != nil && err != io.EOF) {
+ t.Fatalf("first Read: got (%d, %v), wanted (1, nil or EOF)", n, err)
+ }
+ if want := byte('1'); buf[0] != want {
+ t.Errorf("first Read: got byte %c, wanted %c", buf[0], want)
+ }
+
+ // A second read without seeking is still at EOF.
+ n, err = fd.Impl().Read(ctx, ioseq, ReadOptions{})
+ if n != 0 || err != io.EOF {
+ t.Fatalf("second Read: got (%d, %v), wanted (0, EOF)", n, err)
+ }
+
+ // Seeking to the beginning of the file causes it to be regenerated.
+ n, err = fd.Impl().Seek(ctx, 0, linux.SEEK_SET)
+ if n != 0 || err != nil {
+ t.Fatalf("Seek: got (%d, %v), wanted (0, nil)", n, err)
+ }
+ n, err = fd.Impl().Read(ctx, ioseq, ReadOptions{})
+ if n != 1 || (err != nil && err != io.EOF) {
+ t.Fatalf("Read after Seek: got (%d, %v), wanted (1, nil or EOF)", n, err)
+ }
+ if want := byte('2'); buf[0] != want {
+ t.Errorf("Read after Seek: got byte %c, wanted %c", buf[0], want)
+ }
+
+ // PRead at the beginning of the file also causes it to be regenerated.
+ n, err = fd.Impl().PRead(ctx, ioseq, 0, ReadOptions{})
+ if n != 1 || (err != nil && err != io.EOF) {
+ t.Fatalf("PRead: got (%d, %v), wanted (1, nil or EOF)", n, err)
+ }
+ if want := byte('3'); buf[0] != want {
+ t.Errorf("PRead: got byte %c, wanted %c", buf[0], want)
+ }
+}
diff --git a/pkg/sentry/vfs/testutil.go b/pkg/sentry/vfs/testutil.go
new file mode 100644
index 000000000..70b192ece
--- /dev/null
+++ b/pkg/sentry/vfs/testutil.go
@@ -0,0 +1,139 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs
+
+import (
+ "gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/sentry/context"
+ "gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+ "gvisor.dev/gvisor/pkg/syserror"
+)
+
+// FDTestFilesystemType is a test-only FilesystemType that produces Filesystems
+// for which all FilesystemImpl methods taking a path return EPERM. It is used
+// to produce Mounts and Dentries for testing of FileDescriptionImpls that do
+// not depend on their originating Filesystem.
+type FDTestFilesystemType struct{}
+
+// FDTestFilesystem is a test-only FilesystemImpl produced by
+// FDTestFilesystemType.
+type FDTestFilesystem struct {
+ vfsfs Filesystem
+}
+
+// NewFilesystem implements FilesystemType.NewFilesystem.
+func (fstype FDTestFilesystemType) NewFilesystem(ctx context.Context, creds *auth.Credentials, source string, opts NewFilesystemOptions) (*Filesystem, *Dentry, error) {
+ var fs FDTestFilesystem
+ fs.vfsfs.Init(&fs)
+ return &fs.vfsfs, fs.NewDentry(), nil
+}
+
+// Release implements FilesystemImpl.Release.
+func (fs *FDTestFilesystem) Release() {
+}
+
+// Sync implements FilesystemImpl.Sync.
+func (fs *FDTestFilesystem) Sync(ctx context.Context) error {
+ return nil
+}
+
+// GetDentryAt implements FilesystemImpl.GetDentryAt.
+func (fs *FDTestFilesystem) GetDentryAt(ctx context.Context, rp *ResolvingPath, opts GetDentryOptions) (*Dentry, error) {
+ return nil, syserror.EPERM
+}
+
+// LinkAt implements FilesystemImpl.LinkAt.
+func (fs *FDTestFilesystem) LinkAt(ctx context.Context, rp *ResolvingPath, vd VirtualDentry) error {
+ return syserror.EPERM
+}
+
+// MkdirAt implements FilesystemImpl.MkdirAt.
+func (fs *FDTestFilesystem) MkdirAt(ctx context.Context, rp *ResolvingPath, opts MkdirOptions) error {
+ return syserror.EPERM
+}
+
+// MknodAt implements FilesystemImpl.MknodAt.
+func (fs *FDTestFilesystem) MknodAt(ctx context.Context, rp *ResolvingPath, opts MknodOptions) error {
+ return syserror.EPERM
+}
+
+// OpenAt implements FilesystemImpl.OpenAt.
+func (fs *FDTestFilesystem) OpenAt(ctx context.Context, rp *ResolvingPath, opts OpenOptions) (*FileDescription, error) {
+ return nil, syserror.EPERM
+}
+
+// ReadlinkAt implements FilesystemImpl.ReadlinkAt.
+func (fs *FDTestFilesystem) ReadlinkAt(ctx context.Context, rp *ResolvingPath) (string, error) {
+ return "", syserror.EPERM
+}
+
+// RenameAt implements FilesystemImpl.RenameAt.
+func (fs *FDTestFilesystem) RenameAt(ctx context.Context, rp *ResolvingPath, vd VirtualDentry, opts RenameOptions) error {
+ return syserror.EPERM
+}
+
+// RmdirAt implements FilesystemImpl.RmdirAt.
+func (fs *FDTestFilesystem) RmdirAt(ctx context.Context, rp *ResolvingPath) error {
+ return syserror.EPERM
+}
+
+// SetStatAt implements FilesystemImpl.SetStatAt.
+func (fs *FDTestFilesystem) SetStatAt(ctx context.Context, rp *ResolvingPath, opts SetStatOptions) error {
+ return syserror.EPERM
+}
+
+// StatAt implements FilesystemImpl.StatAt.
+func (fs *FDTestFilesystem) StatAt(ctx context.Context, rp *ResolvingPath, opts StatOptions) (linux.Statx, error) {
+ return linux.Statx{}, syserror.EPERM
+}
+
+// StatFSAt implements FilesystemImpl.StatFSAt.
+func (fs *FDTestFilesystem) StatFSAt(ctx context.Context, rp *ResolvingPath) (linux.Statfs, error) {
+ return linux.Statfs{}, syserror.EPERM
+}
+
+// SymlinkAt implements FilesystemImpl.SymlinkAt.
+func (fs *FDTestFilesystem) SymlinkAt(ctx context.Context, rp *ResolvingPath, target string) error {
+ return syserror.EPERM
+}
+
+// UnlinkAt implements FilesystemImpl.UnlinkAt.
+func (fs *FDTestFilesystem) UnlinkAt(ctx context.Context, rp *ResolvingPath) error {
+ return syserror.EPERM
+}
+
+type fdTestDentry struct {
+ vfsd Dentry
+}
+
+// NewDentry returns a new Dentry.
+func (fs *FDTestFilesystem) NewDentry() *Dentry {
+ var d fdTestDentry
+ d.vfsd.Init(&d)
+ return &d.vfsd
+}
+
+// IncRef implements DentryImpl.IncRef.
+func (d *fdTestDentry) IncRef(vfsfs *Filesystem) {
+}
+
+// TryIncRef implements DentryImpl.TryIncRef.
+func (d *fdTestDentry) TryIncRef(vfsfs *Filesystem) bool {
+ return true
+}
+
+// DecRef implements DentryImpl.DecRef.
+func (d *fdTestDentry) DecRef(vfsfs *Filesystem) {
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-02 10:38:51 +0000