From 137f3614009b0ef931c1d00a083b4ae8e6a39bc9 Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Thu, 26 Mar 2020 16:46:15 -0700 Subject: Use host-defined file owner and mode, when possible, for imported fds. Using the host-defined file owner matches VFS1. It is more correct to use the host-defined mode, since the cached value may become out of date. However, kernfs.Inode.Mode() does not return an error--other filesystems on kernfs are in-memory so retrieving mode should not fail. Therefore, if the host syscall fails, we rely on a cached value instead. Updates #1672. PiperOrigin-RevId: 303220864 --- pkg/sentry/control/proc.go | 6 +-- pkg/sentry/fs/host/BUILD | 1 - pkg/sentry/fs/host/control.go | 2 +- pkg/sentry/fs/host/file.go | 10 ++-- pkg/sentry/fs/host/inode_test.go | 3 +- pkg/sentry/fs/host/wait_test.go | 3 +- pkg/sentry/fsimpl/host/host.go | 110 ++++++++++++++++++++++++++------------- 7 files changed, 85 insertions(+), 50 deletions(-) (limited to 'pkg') diff --git a/pkg/sentry/control/proc.go b/pkg/sentry/control/proc.go index 5457ba5e7..b51fb3959 100644 --- a/pkg/sentry/control/proc.go +++ b/pkg/sentry/control/proc.go @@ -224,8 +224,6 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI } } - mounter := fs.FileOwnerFromContext(ctx) - // TODO(gvisor.dev/issue/1623): Use host FD when supported in VFS2. var ttyFile *fs.File for appFD, hostFile := range args.FilePayload.Files { @@ -235,7 +233,7 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI // Import the file as a host TTY file. if ttyFile == nil { var err error - appFile, err = host.ImportFile(ctx, int(hostFile.Fd()), mounter, true /* isTTY */) + appFile, err = host.ImportFile(ctx, int(hostFile.Fd()), true /* isTTY */) if err != nil { return nil, 0, nil, err } @@ -254,7 +252,7 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI } else { // Import the file as a regular host file. var err error - appFile, err = host.ImportFile(ctx, int(hostFile.Fd()), mounter, false /* isTTY */) + appFile, err = host.ImportFile(ctx, int(hostFile.Fd()), false /* isTTY */) if err != nil { return nil, 0, nil, err } diff --git a/pkg/sentry/fs/host/BUILD b/pkg/sentry/fs/host/BUILD index 011625c80..aabce6cc9 100644 --- a/pkg/sentry/fs/host/BUILD +++ b/pkg/sentry/fs/host/BUILD @@ -71,7 +71,6 @@ go_test( "//pkg/fd", "//pkg/fdnotifier", "//pkg/sentry/contexttest", - "//pkg/sentry/fs", "//pkg/sentry/kernel/time", "//pkg/sentry/socket", "//pkg/sentry/socket/unix/transport", diff --git a/pkg/sentry/fs/host/control.go b/pkg/sentry/fs/host/control.go index cd84e1337..52c0504b6 100644 --- a/pkg/sentry/fs/host/control.go +++ b/pkg/sentry/fs/host/control.go @@ -78,7 +78,7 @@ func fdsToFiles(ctx context.Context, fds []int) []*fs.File { } // Create the file backed by hostFD. - file, err := NewFile(ctx, fd, fs.FileOwnerFromContext(ctx)) + file, err := NewFile(ctx, fd) if err != nil { ctx.Warningf("Error creating file from host FD: %v", err) break diff --git a/pkg/sentry/fs/host/file.go b/pkg/sentry/fs/host/file.go index 034862694..3e48b8b2c 100644 --- a/pkg/sentry/fs/host/file.go +++ b/pkg/sentry/fs/host/file.go @@ -60,8 +60,8 @@ var _ fs.FileOperations = (*fileOperations)(nil) // The returned File cannot be saved, since there is no guarantee that the same // FD will exist or represent the same file at time of restore. If such a // guarantee does exist, use ImportFile instead. -func NewFile(ctx context.Context, fd int, mounter fs.FileOwner) (*fs.File, error) { - return newFileFromDonatedFD(ctx, fd, mounter, false, false) +func NewFile(ctx context.Context, fd int) (*fs.File, error) { + return newFileFromDonatedFD(ctx, fd, false, false) } // ImportFile creates a new File backed by the provided host file descriptor. @@ -71,13 +71,13 @@ func NewFile(ctx context.Context, fd int, mounter fs.FileOwner) (*fs.File, error // If the returned file is saved, it will be restored by re-importing the FD // originally passed to ImportFile. It is the restorer's responsibility to // ensure that the FD represents the same file. -func ImportFile(ctx context.Context, fd int, mounter fs.FileOwner, isTTY bool) (*fs.File, error) { - return newFileFromDonatedFD(ctx, fd, mounter, true, isTTY) +func ImportFile(ctx context.Context, fd int, isTTY bool) (*fs.File, error) { + return newFileFromDonatedFD(ctx, fd, true, isTTY) } // newFileFromDonatedFD returns an fs.File from a donated FD. If the FD is // saveable, then saveable is true. -func newFileFromDonatedFD(ctx context.Context, donated int, mounter fs.FileOwner, saveable, isTTY bool) (*fs.File, error) { +func newFileFromDonatedFD(ctx context.Context, donated int, saveable, isTTY bool) (*fs.File, error) { var s syscall.Stat_t if err := syscall.Fstat(donated, &s); err != nil { return nil, err diff --git a/pkg/sentry/fs/host/inode_test.go b/pkg/sentry/fs/host/inode_test.go index 4c374681c..c507f57eb 100644 --- a/pkg/sentry/fs/host/inode_test.go +++ b/pkg/sentry/fs/host/inode_test.go @@ -19,7 +19,6 @@ import ( "testing" "gvisor.dev/gvisor/pkg/sentry/contexttest" - "gvisor.dev/gvisor/pkg/sentry/fs" ) // TestCloseFD verifies fds will be closed. @@ -33,7 +32,7 @@ func TestCloseFD(t *testing.T) { // Use the write-end because we will detect if it's closed on the read end. ctx := contexttest.Context(t) - file, err := NewFile(ctx, p[1], fs.RootOwner) + file, err := NewFile(ctx, p[1]) if err != nil { t.Fatalf("Failed to create File: %v", err) } diff --git a/pkg/sentry/fs/host/wait_test.go b/pkg/sentry/fs/host/wait_test.go index d49c3a635..ce397a5e3 100644 --- a/pkg/sentry/fs/host/wait_test.go +++ b/pkg/sentry/fs/host/wait_test.go @@ -20,7 +20,6 @@ import ( "time" "gvisor.dev/gvisor/pkg/sentry/contexttest" - "gvisor.dev/gvisor/pkg/sentry/fs" "gvisor.dev/gvisor/pkg/waiter" ) @@ -34,7 +33,7 @@ func TestWait(t *testing.T) { defer syscall.Close(fds[1]) ctx := contexttest.Context(t) - file, err := NewFile(ctx, fds[0], fs.RootOwner) + file, err := NewFile(ctx, fds[0]) if err != nil { syscall.Close(fds[0]) t.Fatalf("NewFile failed: %v", err) diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go index a54985ef5..17e3d6e9d 100644 --- a/pkg/sentry/fsimpl/host/host.go +++ b/pkg/sentry/fsimpl/host/host.go @@ -54,7 +54,7 @@ func NewMount(vfsObj *vfs.VirtualFilesystem) (*vfs.Mount, error) { } // ImportFD sets up and returns a vfs.FileDescription from a donated fd. -func ImportFD(mnt *vfs.Mount, hostFD int, ownerUID auth.KUID, ownerGID auth.KGID, isTTY bool) (*vfs.FileDescription, error) { +func ImportFD(mnt *vfs.Mount, hostFD int, isTTY bool) (*vfs.FileDescription, error) { fs, ok := mnt.Filesystem().Impl().(*kernfs.Filesystem) if !ok { return nil, fmt.Errorf("can't import host FDs into filesystems of type %T", mnt.Filesystem().Impl()) @@ -78,8 +78,6 @@ func ImportFD(mnt *vfs.Mount, hostFD int, ownerUID auth.KUID, ownerGID auth.KGID canMap: canMap(uint32(fileType)), ino: fs.NextIno(), mode: fileMode, - uid: ownerUID, - gid: ownerGID, // For simplicity, set offset to 0. Technically, we should // only set to 0 on files that are not seekable (sockets, pipes, etc.), // and use the offset from the host fd otherwise. @@ -135,17 +133,20 @@ type inode struct { // This field is initialized at creation time and is immutable. ino uint64 - // TODO(gvisor.dev/issue/1672): protect mode, uid, and gid with mutex. + // modeMu protects mode. + modeMu sync.Mutex - // mode is the file mode of this inode. Note that this value may become out - // of date if the mode is changed on the host, e.g. with chmod. + // mode is a cached version of the file mode on the host. Note that it may + // become out of date if the mode is changed on the host, e.g. with chmod. + // + // Generally, it is better to retrieve the mode from the host through an + // fstat syscall. We only use this value in inode.Mode(), which cannot + // return an error, if the syscall to host fails. + // + // FIXME(b/152294168): Plumb error into Inode.Mode() return value so we + // can get rid of this. mode linux.FileMode - // uid and gid of the file owner. Note that these refer to the owner of the - // file created on import, not the fd on the host. - uid auth.KUID - gid auth.KGID - // offsetMu protects offset. offsetMu sync.Mutex @@ -168,12 +169,35 @@ func fileFlagsFromHostFD(fd int) (int, error) { // CheckPermissions implements kernfs.Inode. func (i *inode) CheckPermissions(ctx context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error { - return vfs.GenericCheckPermissions(creds, ats, i.mode, i.uid, i.gid) + mode, uid, gid, err := i.getPermissions() + if err != nil { + return err + } + return vfs.GenericCheckPermissions(creds, ats, mode, uid, gid) } // Mode implements kernfs.Inode. func (i *inode) Mode() linux.FileMode { - return i.mode + mode, _, _, err := i.getPermissions() + if err != nil { + return i.mode + } + + return linux.FileMode(mode) +} + +func (i *inode) getPermissions() (linux.FileMode, auth.KUID, auth.KGID, error) { + // Retrieve metadata. + var s syscall.Stat_t + if err := syscall.Fstat(i.hostFD, &s); err != nil { + return 0, 0, 0, err + } + + // Update cached mode. + i.modeMu.Lock() + i.mode = linux.FileMode(s.Mode) + i.modeMu.Unlock() + return linux.FileMode(s.Mode), auth.KUID(s.Uid), auth.KGID(s.Gid), nil } // Stat implements kernfs.Inode. @@ -213,45 +237,51 @@ func (i *inode) Stat(_ *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, erro ls.Attributes = s.Attributes ls.AttributesMask = s.Attributes_mask - if mask|linux.STATX_TYPE != 0 { + if mask&linux.STATX_TYPE != 0 { ls.Mode |= s.Mode & linux.S_IFMT } - if mask|linux.STATX_MODE != 0 { + if mask&linux.STATX_MODE != 0 { ls.Mode |= s.Mode &^ linux.S_IFMT } - if mask|linux.STATX_NLINK != 0 { + if mask&linux.STATX_NLINK != 0 { ls.Nlink = s.Nlink } - if mask|linux.STATX_ATIME != 0 { + if mask&linux.STATX_UID != 0 { + ls.UID = s.Uid + } + if mask&linux.STATX_GID != 0 { + ls.GID = s.Gid + } + if mask&linux.STATX_ATIME != 0 { ls.Atime = unixToLinuxStatxTimestamp(s.Atime) } - if mask|linux.STATX_BTIME != 0 { + if mask&linux.STATX_BTIME != 0 { ls.Btime = unixToLinuxStatxTimestamp(s.Btime) } - if mask|linux.STATX_CTIME != 0 { + if mask&linux.STATX_CTIME != 0 { ls.Ctime = unixToLinuxStatxTimestamp(s.Ctime) } - if mask|linux.STATX_MTIME != 0 { + if mask&linux.STATX_MTIME != 0 { ls.Mtime = unixToLinuxStatxTimestamp(s.Mtime) } - if mask|linux.STATX_SIZE != 0 { + if mask&linux.STATX_SIZE != 0 { ls.Size = s.Size } - if mask|linux.STATX_BLOCKS != 0 { + if mask&linux.STATX_BLOCKS != 0 { ls.Blocks = s.Blocks } - // Use our own internal inode number and file owner. - if mask|linux.STATX_INO != 0 { + // Use our own internal inode number. + if mask&linux.STATX_INO != 0 { ls.Ino = i.ino } - if mask|linux.STATX_UID != 0 { - ls.UID = uint32(i.uid) - } - if mask|linux.STATX_GID != 0 { - ls.GID = uint32(i.gid) - } + // Update cached mode. + if (mask&linux.STATX_TYPE != 0) && (mask&linux.STATX_MODE != 0) { + i.modeMu.Lock() + i.mode = linux.FileMode(s.Mode) + i.modeMu.Unlock() + } return ls, nil } @@ -274,6 +304,8 @@ func (i *inode) fstat(opts vfs.StatOptions) (linux.Statx, error) { Mask: linux.STATX_BASIC_STATS, Blksize: uint32(s.Blksize), Nlink: uint32(s.Nlink), + UID: s.Uid, + GID: s.Gid, Mode: uint16(s.Mode), Size: uint64(s.Size), Blocks: uint64(s.Blocks), @@ -282,15 +314,13 @@ func (i *inode) fstat(opts vfs.StatOptions) (linux.Statx, error) { Mtime: timespecToStatxTimestamp(s.Mtim), } - // Use our own internal inode number and file owner. + // Use our own internal inode number. // // TODO(gvisor.dev/issue/1672): Use a kernfs-specific device number as well. // If we use the device number from the host, it may collide with another // sentry-internal device number. We handle device/inode numbers without // relying on the host to prevent collisions. ls.Ino = i.ino - ls.UID = uint32(i.uid) - ls.GID = uint32(i.gid) return ls, nil } @@ -306,7 +336,11 @@ func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Cre if m&^(linux.STATX_MODE|linux.STATX_SIZE|linux.STATX_ATIME|linux.STATX_MTIME) != 0 { return syserror.EPERM } - if err := vfs.CheckSetStat(ctx, creds, &s, i.Mode(), i.uid, i.gid); err != nil { + mode, uid, gid, err := i.getPermissions() + if err != nil { + return err + } + if err := vfs.CheckSetStat(ctx, creds, &s, mode.Permissions(), uid, gid); err != nil { return err } @@ -314,7 +348,9 @@ func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Cre if err := syscall.Fchmod(i.hostFD, uint32(s.Mode)); err != nil { return err } + i.modeMu.Lock() i.mode = linux.FileMode(s.Mode) + i.modeMu.Unlock() } if m&linux.STATX_SIZE != 0 { if err := syscall.Ftruncate(i.hostFD, int64(s.Size)); err != nil { @@ -351,7 +387,11 @@ func (i *inode) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptio } func (i *inode) open(d *vfs.Dentry, mnt *vfs.Mount) (*vfs.FileDescription, error) { - fileType := i.mode.FileType() + mode, _, _, err := i.getPermissions() + if err != nil { + return nil, err + } + fileType := mode.FileType() if fileType == syscall.S_IFSOCK { if i.isTTY { return nil, errors.New("cannot use host socket as TTY") -- cgit v1.2.3