From 012102eefd2b145ddee774cba28e4fa889fadd49 Mon Sep 17 00:00:00 2001 From: Nicolas Lacasse Date: Wed, 20 Nov 2019 14:54:03 -0800 Subject: Pass OpenTruncate to gofer in Open call when opening file with O_TRUNC. Note that the Sentry still calls Truncate() on the file before calling Open. A new p9 version check was added to ensure that the p9 server can handle the the OpenTruncate flag. If not, then the flag is stripped before sending. PiperOrigin-RevId: 281609112 --- pkg/p9/handlers.go | 18 ++++----- pkg/p9/p9.go | 4 -- pkg/p9/p9test/client_test.go | 78 +++++++++++++++++++++++--------------- pkg/p9/version.go | 8 +++- pkg/sentry/fs/flags.go | 7 ++++ pkg/sentry/fs/gofer/file_state.go | 8 +++- pkg/sentry/fs/gofer/handles.go | 5 ++- pkg/sentry/fs/gofer/inode.go | 18 ++++++--- pkg/sentry/syscalls/linux/flags.go | 1 + 9 files changed, 95 insertions(+), 52 deletions(-) diff --git a/pkg/p9/handlers.go b/pkg/p9/handlers.go index ba9a55d6d..51869c7d6 100644 --- a/pkg/p9/handlers.go +++ b/pkg/p9/handlers.go @@ -272,15 +272,15 @@ func (t *Tlopen) handle(cs *connState) message { return newErr(syscall.EINVAL) } - // Are flags valid? - flags := t.Flags &^ OpenFlagsIgnoreMask - if flags&^OpenFlagsModeMask != 0 { - return newErr(syscall.EINVAL) - } - - // Is this an attempt to open a directory as writable? Don't accept. - if ref.mode.IsDir() && flags != ReadOnly { - return newErr(syscall.EINVAL) + if ref.mode.IsDir() { + // Directory must be opened ReadOnly. + if t.Flags&OpenFlagsModeMask != ReadOnly { + return newErr(syscall.EISDIR) + } + // Directory not truncatable. + if t.Flags&OpenTruncate != 0 { + return newErr(syscall.EISDIR) + } } var ( diff --git a/pkg/p9/p9.go b/pkg/p9/p9.go index 415200d60..d3090535a 100644 --- a/pkg/p9/p9.go +++ b/pkg/p9/p9.go @@ -47,10 +47,6 @@ const ( // OpenTruncate is a Tlopen flag indicating that the opened file should be // truncated. OpenTruncate OpenFlags = 01000 - - // OpenFlagsIgnoreMask is a list of OpenFlags mode bits that are ignored for Tlopen. - // Note that syscall.O_LARGEFILE is set to zero, use value from Linux fcntl.h. - OpenFlagsIgnoreMask OpenFlags = syscall.O_DIRECTORY | syscall.O_NOATIME | 0100000 ) // ConnectFlags is the mode passed to Connect operations. diff --git a/pkg/p9/p9test/client_test.go b/pkg/p9/p9test/client_test.go index 8bbdb2488..6e758148d 100644 --- a/pkg/p9/p9test/client_test.go +++ b/pkg/p9/p9test/client_test.go @@ -1044,11 +1044,11 @@ func TestReaddir(t *testing.T) { if _, err := f.Readdir(0, 1); err != syscall.EINVAL { t.Errorf("readdir got %v, wanted EINVAL", err) } - if _, _, _, err := f.Open(p9.ReadWrite); err != syscall.EINVAL { - t.Errorf("readdir got %v, wanted EINVAL", err) + if _, _, _, err := f.Open(p9.ReadWrite); err != syscall.EISDIR { + t.Errorf("readdir got %v, wanted EISDIR", err) } - if _, _, _, err := f.Open(p9.WriteOnly); err != syscall.EINVAL { - t.Errorf("readdir got %v, wanted EINVAL", err) + if _, _, _, err := f.Open(p9.WriteOnly); err != syscall.EISDIR { + t.Errorf("readdir got %v, wanted EISDIR", err) } backend.EXPECT().Open(p9.ReadOnly).Times(1) if _, _, _, err := f.Open(p9.ReadOnly); err != nil { @@ -1065,75 +1065,93 @@ func TestReaddir(t *testing.T) { func TestOpen(t *testing.T) { type openTest struct { name string - mode p9.OpenFlags + flags p9.OpenFlags err error match func(p9.FileMode) bool } cases := []openTest{ - { - name: "invalid", - mode: ^p9.OpenFlagsModeMask, - err: syscall.EINVAL, - match: func(p9.FileMode) bool { return true }, - }, { name: "not-openable-read-only", - mode: p9.ReadOnly, + flags: p9.ReadOnly, err: syscall.EINVAL, match: func(mode p9.FileMode) bool { return !p9.CanOpen(mode) }, }, { name: "not-openable-write-only", - mode: p9.WriteOnly, + flags: p9.WriteOnly, err: syscall.EINVAL, match: func(mode p9.FileMode) bool { return !p9.CanOpen(mode) }, }, { name: "not-openable-read-write", - mode: p9.ReadWrite, + flags: p9.ReadWrite, err: syscall.EINVAL, match: func(mode p9.FileMode) bool { return !p9.CanOpen(mode) }, }, { name: "directory-read-only", - mode: p9.ReadOnly, + flags: p9.ReadOnly, err: nil, match: func(mode p9.FileMode) bool { return mode.IsDir() }, }, { name: "directory-read-write", - mode: p9.ReadWrite, - err: syscall.EINVAL, + flags: p9.ReadWrite, + err: syscall.EISDIR, match: func(mode p9.FileMode) bool { return mode.IsDir() }, }, { name: "directory-write-only", - mode: p9.WriteOnly, - err: syscall.EINVAL, + flags: p9.WriteOnly, + err: syscall.EISDIR, match: func(mode p9.FileMode) bool { return mode.IsDir() }, }, { name: "read-only", - mode: p9.ReadOnly, + flags: p9.ReadOnly, err: nil, match: func(mode p9.FileMode) bool { return p9.CanOpen(mode) }, }, { name: "write-only", - mode: p9.WriteOnly, + flags: p9.WriteOnly, err: nil, match: func(mode p9.FileMode) bool { return p9.CanOpen(mode) && !mode.IsDir() }, }, { name: "read-write", - mode: p9.ReadWrite, + flags: p9.ReadWrite, + err: nil, + match: func(mode p9.FileMode) bool { return p9.CanOpen(mode) && !mode.IsDir() }, + }, + { + name: "directory-read-only-truncate", + flags: p9.ReadOnly | p9.OpenTruncate, + err: syscall.EISDIR, + match: func(mode p9.FileMode) bool { return mode.IsDir() }, + }, + { + name: "read-only-truncate", + flags: p9.ReadOnly | p9.OpenTruncate, + err: nil, + match: func(mode p9.FileMode) bool { return p9.CanOpen(mode) && !mode.IsDir() }, + }, + { + name: "write-only-truncate", + flags: p9.WriteOnly | p9.OpenTruncate, + err: nil, + match: func(mode p9.FileMode) bool { return p9.CanOpen(mode) && !mode.IsDir() }, + }, + { + name: "read-write-truncate", + flags: p9.ReadWrite | p9.OpenTruncate, err: nil, match: func(mode p9.FileMode) bool { return p9.CanOpen(mode) && !mode.IsDir() }, }, } - // Open(mode OpenFlags) (*fd.FD, QID, uint32, error) + // Open(flags OpenFlags) (*fd.FD, QID, uint32, error) // - only works on Regular, NamedPipe, BLockDevice, CharacterDevice // - returning a file works as expected for name := range newTypeMap(nil) { @@ -1171,25 +1189,25 @@ func TestOpen(t *testing.T) { // Attempt the given open. if tc.err != nil { // We expect an error, just test and return. - if _, _, _, err := f.Open(tc.mode); err != tc.err { - t.Fatalf("open with mode %v got %v, want %v", tc.mode, err, tc.err) + if _, _, _, err := f.Open(tc.flags); err != tc.err { + t.Fatalf("open with flags %v got %v, want %v", tc.flags, err, tc.err) } return } // Run an FD test, since we expect success. fdTest(t, func(send *fd.FD) *fd.FD { - backend.EXPECT().Open(tc.mode).Return(send, p9.QID{}, uint32(0), nil).Times(1) - recv, _, _, err := f.Open(tc.mode) + backend.EXPECT().Open(tc.flags).Return(send, p9.QID{}, uint32(0), nil).Times(1) + recv, _, _, err := f.Open(tc.flags) if err != tc.err { - t.Fatalf("open with mode %v got %v, want %v", tc.mode, err, tc.err) + t.Fatalf("open with flags %v got %v, want %v", tc.flags, err, tc.err) } return recv }) // If the open was successful, attempt another one. - if _, _, _, err := f.Open(tc.mode); err != syscall.EINVAL { - t.Errorf("second open with mode %v got %v, want EINVAL", tc.mode, err) + if _, _, _, err := f.Open(tc.flags); err != syscall.EINVAL { + t.Errorf("second open with flags %v got %v, want EINVAL", tc.flags, err) } // Ensure that all illegal operations fail. diff --git a/pkg/p9/version.go b/pkg/p9/version.go index f1ffdd23a..36a694c58 100644 --- a/pkg/p9/version.go +++ b/pkg/p9/version.go @@ -26,7 +26,7 @@ const ( // // Clients are expected to start requesting this version number and // to continuously decrement it until a Tversion request succeeds. - highestSupportedVersion uint32 = 8 + highestSupportedVersion uint32 = 9 // lowestSupportedVersion is the lowest supported version X in a // version string of the format 9P2000.L.Google.X. @@ -155,3 +155,9 @@ func versionSupportsTallocate(v uint32) bool { func versionSupportsFlipcall(v uint32) bool { return v >= 8 } + +// VersionSupportsOpenTruncateFlag returns true if version v supports +// passing the OpenTruncate flag to Tlopen. +func VersionSupportsOpenTruncateFlag(v uint32) bool { + return v >= 9 +} diff --git a/pkg/sentry/fs/flags.go b/pkg/sentry/fs/flags.go index 0fab876a9..4338ae1fa 100644 --- a/pkg/sentry/fs/flags.go +++ b/pkg/sentry/fs/flags.go @@ -64,6 +64,10 @@ type FileFlags struct { // NonSeekable indicates that file.offset isn't used. NonSeekable bool + + // Truncate indicates that the file should be truncated before opened. + // This is only applicable if the file is regular. + Truncate bool } // SettableFileFlags is a subset of FileFlags above that can be changed @@ -118,6 +122,9 @@ func (f FileFlags) ToLinux() (mask uint) { if f.LargeFile { mask |= linux.O_LARGEFILE } + if f.Truncate { + mask |= linux.O_TRUNC + } switch { case f.Read && f.Write: diff --git a/pkg/sentry/fs/gofer/file_state.go b/pkg/sentry/fs/gofer/file_state.go index c2fbb4be9..bb8312849 100644 --- a/pkg/sentry/fs/gofer/file_state.go +++ b/pkg/sentry/fs/gofer/file_state.go @@ -28,8 +28,14 @@ func (f *fileOperations) afterLoad() { // Manually load the open handles. var err error + + // The file may have been opened with Truncate, but we don't + // want to re-open it with Truncate or we will lose data. + flags := f.flags + flags.Truncate = false + // TODO(b/38173783): Context is not plumbed to save/restore. - f.handles, err = f.inodeOperations.fileState.getHandles(context.Background(), f.flags, f.inodeOperations.cachingInodeOps) + f.handles, err = f.inodeOperations.fileState.getHandles(context.Background(), flags, f.inodeOperations.cachingInodeOps) if err != nil { return fmt.Errorf("failed to re-open handle: %v", err) } diff --git a/pkg/sentry/fs/gofer/handles.go b/pkg/sentry/fs/gofer/handles.go index 39c8ec33d..b86c49b39 100644 --- a/pkg/sentry/fs/gofer/handles.go +++ b/pkg/sentry/fs/gofer/handles.go @@ -64,7 +64,7 @@ func (h *handles) DecRef() { }) } -func newHandles(ctx context.Context, file contextFile, flags fs.FileFlags) (*handles, error) { +func newHandles(ctx context.Context, client *p9.Client, file contextFile, flags fs.FileFlags) (*handles, error) { _, newFile, err := file.walk(ctx, nil) if err != nil { return nil, err @@ -81,6 +81,9 @@ func newHandles(ctx context.Context, file contextFile, flags fs.FileFlags) (*han default: panic("impossible fs.FileFlags") } + if flags.Truncate && p9.VersionSupportsOpenTruncateFlag(client.Version()) { + p9flags |= p9.OpenTruncate + } hostFile, _, _, err := newFile.open(ctx, p9flags) if err != nil { diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go index 99910388f..4237bf353 100644 --- a/pkg/sentry/fs/gofer/inode.go +++ b/pkg/sentry/fs/gofer/inode.go @@ -180,7 +180,7 @@ func (i *inodeFileState) setSharedHandlesLocked(flags fs.FileFlags, h *handles) // given flags. func (i *inodeFileState) getHandles(ctx context.Context, flags fs.FileFlags, cache *fsutil.CachingInodeOperations) (*handles, error) { if !i.canShareHandles() { - return newHandles(ctx, i.file, flags) + return newHandles(ctx, i.s.client, i.file, flags) } i.handlesMu.Lock() @@ -201,19 +201,25 @@ func (i *inodeFileState) getHandles(ctx context.Context, flags fs.FileFlags, cac // whether previously open read handle was recreated. Host mappings must be // invalidated if so. func (i *inodeFileState) getHandlesLocked(ctx context.Context, flags fs.FileFlags) (*handles, bool, error) { - // Do we already have usable shared handles? - if flags.Write { + // Check if we are able to use cached handles. + if flags.Truncate && p9.VersionSupportsOpenTruncateFlag(i.s.client.Version()) { + // If we are truncating (and the gofer supports it), then we + // always need a new handle. Don't return one from the cache. + } else if flags.Write { if i.writeHandles != nil && (i.writeHandlesRW || !flags.Read) { + // File is opened for writing, and we have cached write + // handles that we can use. i.writeHandles.IncRef() return i.writeHandles, false, nil } } else if i.readHandles != nil { + // File is opened for reading and we have cached handles. i.readHandles.IncRef() return i.readHandles, false, nil } - // No; get new handles and cache them for future sharing. - h, err := newHandles(ctx, i.file, flags) + // Get new handles and cache them for future sharing. + h, err := newHandles(ctx, i.s.client, i.file, flags) if err != nil { return nil, false, err } @@ -239,7 +245,7 @@ func (i *inodeFileState) recreateReadHandles(ctx context.Context, writer *handle if !flags.Read { // Writer can't be used for read, must create a new handle. var err error - h, err = newHandles(ctx, i.file, fs.FileFlags{Read: true}) + h, err = newHandles(ctx, i.s.client, i.file, fs.FileFlags{Read: true}) if err != nil { return err } diff --git a/pkg/sentry/syscalls/linux/flags.go b/pkg/sentry/syscalls/linux/flags.go index 444f2b004..07961dad9 100644 --- a/pkg/sentry/syscalls/linux/flags.go +++ b/pkg/sentry/syscalls/linux/flags.go @@ -50,5 +50,6 @@ func linuxToFlags(mask uint) fs.FileFlags { Directory: mask&linux.O_DIRECTORY != 0, Async: mask&linux.O_ASYNC != 0, LargeFile: mask&linux.O_LARGEFILE != 0, + Truncate: mask&linux.O_TRUNC != 0, } } -- cgit v1.2.3