650 lines
20 KiB
Go
650 lines
20 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fs
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import (
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"strings"
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"gvisor.googlesource.com/gvisor/pkg/abi/linux"
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"gvisor.googlesource.com/gvisor/pkg/log"
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"gvisor.googlesource.com/gvisor/pkg/sentry/context"
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"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
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"gvisor.googlesource.com/gvisor/pkg/syserror"
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)
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func overlayHasWhiteout(parent *Inode, name string) bool {
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buf, err := parent.Getxattr(XattrOverlayWhiteout(name))
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return err == nil && string(buf) == "y"
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}
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func overlayCreateWhiteout(parent *Inode, name string) error {
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return parent.InodeOperations.Setxattr(parent, XattrOverlayWhiteout(name), []byte("y"))
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}
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func overlayWriteOut(ctx context.Context, o *overlayEntry) error {
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// Hot path. Avoid defers.
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var err error
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o.copyMu.RLock()
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if o.upper != nil {
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err = o.upper.InodeOperations.WriteOut(ctx, o.upper)
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}
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o.copyMu.RUnlock()
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return err
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}
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func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name string) (*Dirent, error) {
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// Hot path. Avoid defers.
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parent.copyMu.RLock()
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// Assert that there is at least one upper or lower entry.
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if parent.upper == nil && parent.lower == nil {
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parent.copyMu.RUnlock()
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panic("invalid overlayEntry, needs at least one Inode")
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}
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var upperInode *Inode
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var lowerInode *Inode
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// We must remember whether the upper fs returned a negative dirent,
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// because it is only safe to return one if the upper did.
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var negativeUpperChild bool
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// Does the parent directory exist in the upper file system?
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if parent.upper != nil {
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// First check if a file object exists in the upper file system.
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// A file could have been created over a whiteout, so we need to
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// check if something exists in the upper file system first.
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child, err := parent.upper.Lookup(ctx, name)
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if err != nil && err != syserror.ENOENT {
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// We encountered an error that an overlay cannot handle,
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// we must propagate it to the caller.
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parent.copyMu.RUnlock()
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return nil, err
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}
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if child != nil {
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if child.IsNegative() {
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negativeUpperChild = true
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} else {
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upperInode = child.Inode
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upperInode.IncRef()
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}
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child.DecRef()
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}
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// Are we done?
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if overlayHasWhiteout(parent.upper, name) {
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if upperInode == nil {
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parent.copyMu.RUnlock()
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if negativeUpperChild {
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// If the upper fs returnd a negative
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// Dirent, then the upper is OK with
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// that negative Dirent being cached in
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// the Dirent tree, so we can return
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// one from the overlay.
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return NewNegativeDirent(name), nil
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}
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// Upper fs is not OK with a negative Dirent
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// being cached in the Dirent tree, so don't
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// return one.
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return nil, syserror.ENOENT
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}
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entry, err := newOverlayEntry(ctx, upperInode, nil, false)
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if err != nil {
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// Don't leak resources.
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upperInode.DecRef()
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parent.copyMu.RUnlock()
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return nil, err
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}
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d, err := NewDirent(newOverlayInode(ctx, entry, inode.MountSource), name), nil
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parent.copyMu.RUnlock()
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return d, err
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}
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}
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// Check the lower file system. We do this unconditionally (even for
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// non-directories) because we may need to use stable attributes from
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// the lower filesystem (e.g. device number, inode number) that were
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// visible before a copy up.
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if parent.lower != nil {
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// Check the lower file system.
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child, err := parent.lower.Lookup(ctx, name)
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// Same song and dance as above.
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if err != nil && err != syserror.ENOENT {
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// Don't leak resources.
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if upperInode != nil {
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upperInode.DecRef()
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}
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parent.copyMu.RUnlock()
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return nil, err
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}
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if child != nil {
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if !child.IsNegative() {
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if upperInode == nil {
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// If nothing was in the upper, use what we found in the lower.
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lowerInode = child.Inode
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lowerInode.IncRef()
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} else {
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// If we have something from the upper, we can only use it if the types
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// match.
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// NOTE: Allow SpecialDirectories and Directories to merge.
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// This is needed to allow submounts in /proc and /sys.
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if upperInode.StableAttr.Type == child.Inode.StableAttr.Type ||
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(IsDir(upperInode.StableAttr) && IsDir(child.Inode.StableAttr)) {
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lowerInode = child.Inode
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lowerInode.IncRef()
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}
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}
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}
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child.DecRef()
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}
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}
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// Was all of this for naught?
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if upperInode == nil && lowerInode == nil {
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parent.copyMu.RUnlock()
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// We can only return a negative dirent if the upper returned
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// one as well. See comments above regarding negativeUpperChild
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// for more info.
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if negativeUpperChild {
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return NewNegativeDirent(name), nil
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}
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return nil, syserror.ENOENT
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}
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// Did we find a lower Inode? Remember this because we may decide we don't
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// actually need the lower Inode (see below).
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lowerExists := lowerInode != nil
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// If we found something in the upper filesystem and the lower filesystem,
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// use the stable attributes from the lower filesystem. If we don't do this,
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// then it may appear that the file was magically recreated across copy up.
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if upperInode != nil && lowerInode != nil {
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// Steal attributes.
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upperInode.StableAttr = lowerInode.StableAttr
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// For non-directories, the lower filesystem resource is strictly
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// unnecessary because we don't need to copy-up and we will always
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// operate (e.g. read/write) on the upper Inode.
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if !IsDir(upperInode.StableAttr) {
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lowerInode.DecRef()
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lowerInode = nil
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}
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}
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// Phew, finally done.
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entry, err := newOverlayEntry(ctx, upperInode, lowerInode, lowerExists)
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if err != nil {
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// Well, not quite, we failed at the last moment, how depressing.
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// Be sure not to leak resources.
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if upperInode != nil {
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upperInode.DecRef()
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}
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if lowerInode != nil {
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lowerInode.DecRef()
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}
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parent.copyMu.RUnlock()
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return nil, err
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}
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d, err := NewDirent(newOverlayInode(ctx, entry, inode.MountSource), name), nil
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parent.copyMu.RUnlock()
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return d, err
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}
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func overlayCreate(ctx context.Context, o *overlayEntry, parent *Dirent, name string, flags FileFlags, perm FilePermissions) (*File, error) {
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// Dirent.Create takes renameMu if the Inode is an overlay Inode.
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if err := copyUpLockedForRename(ctx, parent); err != nil {
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return nil, err
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}
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upperFile, err := o.upper.InodeOperations.Create(ctx, o.upper, name, flags, perm)
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if err != nil {
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return nil, err
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}
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// Take another reference on the upper file's inode, which will be
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// owned by the overlay entry.
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upperFile.Dirent.Inode.IncRef()
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entry, err := newOverlayEntry(ctx, upperFile.Dirent.Inode, nil, false)
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if err != nil {
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cleanupUpper(ctx, o.upper, name)
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return nil, err
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}
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// NOTE: Replace the Dirent with a transient Dirent, since
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// we are about to create the real Dirent: an overlay Dirent.
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//
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// This ensures the *fs.File returned from overlayCreate is in the same
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// state as the *fs.File returned by overlayGetFile, where the upper
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// file has a transient Dirent.
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//
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// This is necessary for Save/Restore, as otherwise the upper Dirent
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// (which has no path as it is unparented and never reachable by the
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// user) will clobber the real path for the underlying Inode.
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upperFile.Dirent.Inode.IncRef()
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upperDirent := NewTransientDirent(upperFile.Dirent.Inode)
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upperFile.Dirent.DecRef()
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upperFile.Dirent = upperDirent
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// Create the overlay inode and dirent. We need this to construct the
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// overlay file.
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overlayInode := newOverlayInode(ctx, entry, parent.Inode.MountSource)
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// d will own the inode reference.
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overlayDirent := NewDirent(overlayInode, name)
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// The overlay file created below with NewFile will take a reference on
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// the overlayDirent, and it should be the only thing holding a
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// reference at the time of creation, so we must drop this reference.
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defer overlayDirent.DecRef()
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// Create a new overlay file that wraps the upper file.
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flags.Pread = upperFile.Flags().Pread
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flags.Pwrite = upperFile.Flags().Pwrite
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overlayFile := NewFile(ctx, overlayDirent, flags, &overlayFileOperations{upper: upperFile})
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return overlayFile, nil
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}
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func overlayCreateDirectory(ctx context.Context, o *overlayEntry, parent *Dirent, name string, perm FilePermissions) error {
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// Dirent.CreateDirectory takes renameMu if the Inode is an overlay
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// Inode.
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if err := copyUpLockedForRename(ctx, parent); err != nil {
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return err
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}
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return o.upper.InodeOperations.CreateDirectory(ctx, o.upper, name, perm)
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}
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func overlayCreateLink(ctx context.Context, o *overlayEntry, parent *Dirent, oldname string, newname string) error {
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// Dirent.CreateLink takes renameMu if the Inode is an overlay Inode.
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if err := copyUpLockedForRename(ctx, parent); err != nil {
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return err
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}
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return o.upper.InodeOperations.CreateLink(ctx, o.upper, oldname, newname)
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}
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func overlayCreateHardLink(ctx context.Context, o *overlayEntry, parent *Dirent, target *Dirent, name string) error {
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// Dirent.CreateHardLink takes renameMu if the Inode is an overlay
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// Inode.
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if err := copyUpLockedForRename(ctx, parent); err != nil {
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return err
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}
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if err := copyUpLockedForRename(ctx, target); err != nil {
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return err
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}
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return o.upper.InodeOperations.CreateHardLink(ctx, o.upper, target.Inode.overlay.upper, name)
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}
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func overlayCreateFifo(ctx context.Context, o *overlayEntry, parent *Dirent, name string, perm FilePermissions) error {
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// Dirent.CreateFifo takes renameMu if the Inode is an overlay Inode.
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if err := copyUpLockedForRename(ctx, parent); err != nil {
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return err
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}
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return o.upper.InodeOperations.CreateFifo(ctx, o.upper, name, perm)
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}
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func overlayRemove(ctx context.Context, o *overlayEntry, parent *Dirent, child *Dirent) error {
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// Dirent.Remove and Dirent.RemoveDirectory take renameMu if the Inode
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// is an overlay Inode.
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if err := copyUpLockedForRename(ctx, parent); err != nil {
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return err
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}
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child.Inode.overlay.copyMu.RLock()
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defer child.Inode.overlay.copyMu.RUnlock()
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if child.Inode.overlay.upper != nil {
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if child.Inode.StableAttr.Type == Directory {
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if err := o.upper.InodeOperations.RemoveDirectory(ctx, o.upper, child.name); err != nil {
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return err
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}
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} else {
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if err := o.upper.InodeOperations.Remove(ctx, o.upper, child.name); err != nil {
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return err
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}
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}
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}
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if child.Inode.overlay.lowerExists {
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return overlayCreateWhiteout(o.upper, child.name)
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}
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return nil
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}
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func overlayRename(ctx context.Context, o *overlayEntry, oldParent *Dirent, renamed *Dirent, newParent *Dirent, newName string) error {
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// To be able to copy these up below, they have to be part of an
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// overlay file system.
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//
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// Maybe some day we can allow the more complicated case of
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// non-overlay X overlay renames, but that's not necessary right now.
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if renamed.Inode.overlay == nil || newParent.Inode.overlay == nil || oldParent.Inode.overlay == nil {
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return syserror.EXDEV
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}
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// Check here if the file to be replaced exists and is a non-empty
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// directory. If we copy up first, we may end up copying the directory
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// but none of its children, so the directory will appear empty in the
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// upper fs, which will then allow the rename to proceed when it should
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// return ENOTEMPTY.
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replaced, err := newParent.Inode.Lookup(ctx, newName)
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if err != nil && err != syserror.ENOENT {
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return err
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}
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if err == nil {
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// NOTE: We must drop the reference on replaced before we make
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// the rename call. For that reason we can't use defer.
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if !replaced.IsNegative() && IsDir(replaced.Inode.StableAttr) {
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children, err := readdirOne(ctx, replaced)
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if err != nil {
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replaced.DecRef()
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return err
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}
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// readdirOne ensures that "." and ".." are not
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// included among the returned children, so we don't
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// need to bother checking for them.
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if len(children) > 0 {
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replaced.DecRef()
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return syserror.ENOTEMPTY
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}
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}
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replaced.DecRef()
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}
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if err := copyUpLockedForRename(ctx, renamed); err != nil {
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return err
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}
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if err := copyUpLockedForRename(ctx, newParent); err != nil {
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return err
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}
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oldName := renamed.name
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if err := o.upper.InodeOperations.Rename(ctx, oldParent.Inode.overlay.upper, oldName, newParent.Inode.overlay.upper, newName); err != nil {
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return err
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}
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if renamed.Inode.overlay.lowerExists {
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return overlayCreateWhiteout(oldParent.Inode.overlay.upper, oldName)
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}
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return nil
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}
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func overlayBind(ctx context.Context, o *overlayEntry, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
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o.copyMu.RLock()
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defer o.copyMu.RUnlock()
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// We do not support doing anything exciting with sockets unless there
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// is already a directory in the upper filesystem.
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if o.upper == nil {
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return nil, syserror.EOPNOTSUPP
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}
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d, err := o.upper.InodeOperations.Bind(ctx, o.upper, name, data, perm)
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if err != nil {
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return nil, err
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}
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// Grab the inode and drop the dirent, we don't need it.
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inode := d.Inode
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inode.IncRef()
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d.DecRef()
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// Create a new overlay entry and dirent for the socket.
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entry, err := newOverlayEntry(ctx, inode, nil, false)
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if err != nil {
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inode.DecRef()
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return nil, err
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}
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return NewDirent(newOverlayInode(ctx, entry, inode.MountSource), name), nil
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}
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func overlayBoundEndpoint(o *overlayEntry, path string) transport.BoundEndpoint {
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o.copyMu.RLock()
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defer o.copyMu.RUnlock()
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if o.upper != nil {
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return o.upper.InodeOperations.BoundEndpoint(o.upper, path)
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}
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// If the lower is itself an overlay, recurse.
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if o.lower.overlay != nil {
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return overlayBoundEndpoint(o.lower.overlay, path)
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}
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// Lower is not an overlay. Call BoundEndpoint directly.
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return o.lower.InodeOperations.BoundEndpoint(o.lower, path)
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}
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func overlayGetFile(ctx context.Context, o *overlayEntry, d *Dirent, flags FileFlags) (*File, error) {
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// Hot path. Avoid defers.
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if flags.Write {
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if err := copyUp(ctx, d); err != nil {
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return nil, err
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}
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}
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o.copyMu.RLock()
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if o.upper != nil {
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upper, err := overlayFile(ctx, o.upper, flags)
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if err != nil {
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o.copyMu.RUnlock()
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return nil, err
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}
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flags.Pread = upper.Flags().Pread
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flags.Pwrite = upper.Flags().Pwrite
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f, err := NewFile(ctx, d, flags, &overlayFileOperations{upper: upper}), nil
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o.copyMu.RUnlock()
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return f, err
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}
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lower, err := overlayFile(ctx, o.lower, flags)
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if err != nil {
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o.copyMu.RUnlock()
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return nil, err
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}
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flags.Pread = lower.Flags().Pread
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flags.Pwrite = lower.Flags().Pwrite
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o.copyMu.RUnlock()
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return NewFile(ctx, d, flags, &overlayFileOperations{lower: lower}), nil
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}
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func overlayUnstableAttr(ctx context.Context, o *overlayEntry) (UnstableAttr, error) {
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// Hot path. Avoid defers.
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var (
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attr UnstableAttr
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err error
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)
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o.copyMu.RLock()
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if o.upper != nil {
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attr, err = o.upper.UnstableAttr(ctx)
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} else {
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attr, err = o.lower.UnstableAttr(ctx)
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}
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o.copyMu.RUnlock()
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return attr, err
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}
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func overlayGetxattr(o *overlayEntry, name string) ([]byte, error) {
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// Hot path. This is how the overlay checks for whiteout files.
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// Avoid defers.
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var (
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b []byte
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err error
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)
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// Don't forward the value of the extended attribute if it would
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// unexpectedly change the behavior of a wrapping overlay layer.
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if strings.HasPrefix(XattrOverlayPrefix, name) {
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return nil, syserror.ENODATA
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}
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o.copyMu.RLock()
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if o.upper != nil {
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b, err = o.upper.Getxattr(name)
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} else {
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b, err = o.lower.Getxattr(name)
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}
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o.copyMu.RUnlock()
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return b, err
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}
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func overlayListxattr(o *overlayEntry) (map[string]struct{}, error) {
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o.copyMu.RLock()
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defer o.copyMu.RUnlock()
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var names map[string]struct{}
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var err error
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if o.upper != nil {
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names, err = o.upper.Listxattr()
|
|
} else {
|
|
names, err = o.lower.Listxattr()
|
|
}
|
|
for name := range names {
|
|
// Same as overlayGetxattr, we shouldn't forward along
|
|
// overlay attributes.
|
|
if strings.HasPrefix(XattrOverlayPrefix, name) {
|
|
delete(names, name)
|
|
}
|
|
}
|
|
return names, err
|
|
}
|
|
|
|
func overlayCheck(ctx context.Context, o *overlayEntry, p PermMask) error {
|
|
o.copyMu.RLock()
|
|
// Hot path. Avoid defers.
|
|
var err error
|
|
if o.upper != nil {
|
|
err = o.upper.check(ctx, p)
|
|
} else {
|
|
if p.Write {
|
|
// Since writes will be redirected to the upper filesystem, the lower
|
|
// filesystem need not be writable, but must be readable for copy-up.
|
|
p.Write = false
|
|
p.Read = true
|
|
}
|
|
err = o.lower.check(ctx, p)
|
|
}
|
|
o.copyMu.RUnlock()
|
|
return err
|
|
}
|
|
|
|
func overlaySetPermissions(ctx context.Context, o *overlayEntry, d *Dirent, f FilePermissions) bool {
|
|
if err := copyUp(ctx, d); err != nil {
|
|
return false
|
|
}
|
|
return o.upper.InodeOperations.SetPermissions(ctx, o.upper, f)
|
|
}
|
|
|
|
func overlaySetOwner(ctx context.Context, o *overlayEntry, d *Dirent, owner FileOwner) error {
|
|
if err := copyUp(ctx, d); err != nil {
|
|
return err
|
|
}
|
|
return o.upper.InodeOperations.SetOwner(ctx, o.upper, owner)
|
|
}
|
|
|
|
func overlaySetTimestamps(ctx context.Context, o *overlayEntry, d *Dirent, ts TimeSpec) error {
|
|
if err := copyUp(ctx, d); err != nil {
|
|
return err
|
|
}
|
|
return o.upper.InodeOperations.SetTimestamps(ctx, o.upper, ts)
|
|
}
|
|
|
|
func overlayTruncate(ctx context.Context, o *overlayEntry, d *Dirent, size int64) error {
|
|
if err := copyUp(ctx, d); err != nil {
|
|
return err
|
|
}
|
|
return o.upper.InodeOperations.Truncate(ctx, o.upper, size)
|
|
}
|
|
|
|
func overlayReadlink(ctx context.Context, o *overlayEntry) (string, error) {
|
|
o.copyMu.RLock()
|
|
defer o.copyMu.RUnlock()
|
|
if o.upper != nil {
|
|
return o.upper.Readlink(ctx)
|
|
}
|
|
return o.lower.Readlink(ctx)
|
|
}
|
|
|
|
func overlayGetlink(ctx context.Context, o *overlayEntry) (*Dirent, error) {
|
|
var dirent *Dirent
|
|
var err error
|
|
|
|
o.copyMu.RLock()
|
|
defer o.copyMu.RUnlock()
|
|
|
|
if o.upper != nil {
|
|
dirent, err = o.upper.Getlink(ctx)
|
|
} else {
|
|
dirent, err = o.lower.Getlink(ctx)
|
|
}
|
|
if dirent != nil {
|
|
// This dirent is likely bogus (its Inode likely doesn't contain
|
|
// the right overlayEntry). So we're forced to drop it on the
|
|
// ground and claim that jumping around the filesystem like this
|
|
// is not supported.
|
|
name, _ := dirent.FullName(nil)
|
|
dirent.DecRef()
|
|
|
|
// Claim that the path is not accessible.
|
|
err = syserror.EACCES
|
|
log.Warningf("Getlink not supported in overlay for %q", name)
|
|
}
|
|
return nil, err
|
|
}
|
|
|
|
func overlayStatFS(ctx context.Context, o *overlayEntry) (Info, error) {
|
|
o.copyMu.RLock()
|
|
defer o.copyMu.RUnlock()
|
|
|
|
var i Info
|
|
var err error
|
|
if o.upper != nil {
|
|
i, err = o.upper.StatFS(ctx)
|
|
} else {
|
|
i, err = o.lower.StatFS(ctx)
|
|
}
|
|
if err != nil {
|
|
return Info{}, err
|
|
}
|
|
|
|
i.Type = linux.OVERLAYFS_SUPER_MAGIC
|
|
|
|
return i, nil
|
|
}
|
|
|
|
// NewTestOverlayDir returns an overlay Inode for tests.
|
|
//
|
|
// If `revalidate` is true, then the upper filesystem will require
|
|
// revalidation.
|
|
func NewTestOverlayDir(ctx context.Context, upper, lower *Inode, revalidate bool) *Inode {
|
|
fs := &overlayFilesystem{}
|
|
var upperMsrc *MountSource
|
|
if revalidate {
|
|
upperMsrc = NewRevalidatingMountSource(fs, MountSourceFlags{})
|
|
} else {
|
|
upperMsrc = NewNonCachingMountSource(fs, MountSourceFlags{})
|
|
}
|
|
msrc := NewMountSource(&overlayMountSourceOperations{
|
|
upper: upperMsrc,
|
|
lower: NewNonCachingMountSource(fs, MountSourceFlags{}),
|
|
}, fs, MountSourceFlags{})
|
|
overlay := &overlayEntry{
|
|
upper: upper,
|
|
lower: lower,
|
|
}
|
|
return newOverlayInode(ctx, overlay, msrc)
|
|
}
|
|
|
|
// TestHasUpperFS returns true if i is an overlay Inode and it has a pointer
|
|
// to an Inode on an upper filesystem.
|
|
func (i *Inode) TestHasUpperFS() bool {
|
|
return i.overlay != nil && i.overlay.upper != nil
|
|
}
|
|
|
|
// TestHasLowerFS returns true if i is an overlay Inode and it has a pointer
|
|
// to an Inode on a lower filesystem.
|
|
func (i *Inode) TestHasLowerFS() bool {
|
|
return i.overlay != nil && i.overlay.lower != nil
|
|
}
|