From 5da4270a884e9f0c88d583da34f757783f314645 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Wed, 1 Sep 2021 13:05:27 -0700 Subject: Propagate vfs.MkdirOptions.ForSyntheticMountpoint to overlay copy-up. PiperOrigin-RevId: 394296687 --- pkg/sentry/fsimpl/overlay/copy_up.go | 9 +++++++-- pkg/sentry/fsimpl/overlay/filesystem.go | 28 ++++++++++++++++++++-------- 2 files changed, 27 insertions(+), 10 deletions(-) (limited to 'pkg/sentry/fsimpl/overlay') diff --git a/pkg/sentry/fsimpl/overlay/copy_up.go b/pkg/sentry/fsimpl/overlay/copy_up.go index 618092ef1..520487066 100644 --- a/pkg/sentry/fsimpl/overlay/copy_up.go +++ b/pkg/sentry/fsimpl/overlay/copy_up.go @@ -36,6 +36,10 @@ func (d *dentry) isCopiedUp() bool { // // Preconditions: filesystem.renameMu must be locked. func (d *dentry) copyUpLocked(ctx context.Context) error { + return d.copyUpMaybeSyntheticMountpointLocked(ctx, false /* forSyntheticMountpoint */) +} + +func (d *dentry) copyUpMaybeSyntheticMountpointLocked(ctx context.Context, forSyntheticMountpoint bool) error { // Fast path. if d.isCopiedUp() { return nil @@ -59,7 +63,7 @@ func (d *dentry) copyUpLocked(ctx context.Context) error { // d is a filesystem root with no upper layer. return linuxerr.EROFS } - if err := d.parent.copyUpLocked(ctx); err != nil { + if err := d.parent.copyUpMaybeSyntheticMountpointLocked(ctx, forSyntheticMountpoint); err != nil { return err } @@ -168,7 +172,8 @@ func (d *dentry) copyUpLocked(ctx context.Context) error { case linux.S_IFDIR: if err := vfsObj.MkdirAt(ctx, d.fs.creds, &newpop, &vfs.MkdirOptions{ - Mode: linux.FileMode(d.mode &^ linux.S_IFMT), + Mode: linux.FileMode(d.mode &^ linux.S_IFMT), + ForSyntheticMountpoint: forSyntheticMountpoint, }); err != nil { return err } diff --git a/pkg/sentry/fsimpl/overlay/filesystem.go b/pkg/sentry/fsimpl/overlay/filesystem.go index c04c80590..3b3dcf836 100644 --- a/pkg/sentry/fsimpl/overlay/filesystem.go +++ b/pkg/sentry/fsimpl/overlay/filesystem.go @@ -462,13 +462,21 @@ func (fs *filesystem) resolveLocked(ctx context.Context, rp *vfs.ResolvingPath, return d, nil } +type createType int + +const ( + createNonDirectory createType = iota + createDirectory + createSyntheticMountpoint +) + // doCreateAt checks that creating a file at rp is permitted, then invokes // create to do so. // // Preconditions: // * !rp.Done(). // * For the final path component in rp, !rp.ShouldFollowSymlink(). -func (fs *filesystem) doCreateAt(ctx context.Context, rp *vfs.ResolvingPath, dir bool, create func(parent *dentry, name string, haveUpperWhiteout bool) error) error { +func (fs *filesystem) doCreateAt(ctx context.Context, rp *vfs.ResolvingPath, ct createType, create func(parent *dentry, name string, haveUpperWhiteout bool) error) error { var ds *[]*dentry fs.renameMu.RLock() defer fs.renameMuRUnlockAndCheckDrop(ctx, &ds) @@ -504,7 +512,7 @@ func (fs *filesystem) doCreateAt(ctx context.Context, rp *vfs.ResolvingPath, dir return linuxerr.EEXIST } - if !dir && rp.MustBeDir() { + if ct == createNonDirectory && rp.MustBeDir() { return linuxerr.ENOENT } @@ -518,7 +526,7 @@ func (fs *filesystem) doCreateAt(ctx context.Context, rp *vfs.ResolvingPath, dir } // Ensure that the parent directory is copied-up so that we can create the // new file in the upper layer. - if err := parent.copyUpLocked(ctx); err != nil { + if err := parent.copyUpMaybeSyntheticMountpointLocked(ctx, ct == createSyntheticMountpoint); err != nil { return err } @@ -529,7 +537,7 @@ func (fs *filesystem) doCreateAt(ctx context.Context, rp *vfs.ResolvingPath, dir parent.dirents = nil ev := linux.IN_CREATE - if dir { + if ct != createNonDirectory { ev |= linux.IN_ISDIR } parent.watches.Notify(ctx, name, uint32(ev), 0 /* cookie */, vfs.InodeEvent, false /* unlinked */) @@ -618,7 +626,7 @@ func (fs *filesystem) GetParentDentryAt(ctx context.Context, rp *vfs.ResolvingPa // LinkAt implements vfs.FilesystemImpl.LinkAt. func (fs *filesystem) LinkAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs.VirtualDentry) error { - return fs.doCreateAt(ctx, rp, false /* dir */, func(parent *dentry, childName string, haveUpperWhiteout bool) error { + return fs.doCreateAt(ctx, rp, createNonDirectory, func(parent *dentry, childName string, haveUpperWhiteout bool) error { if rp.Mount() != vd.Mount() { return linuxerr.EXDEV } @@ -671,7 +679,11 @@ func (fs *filesystem) LinkAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs. // MkdirAt implements vfs.FilesystemImpl.MkdirAt. func (fs *filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.MkdirOptions) error { - return fs.doCreateAt(ctx, rp, true /* dir */, func(parent *dentry, childName string, haveUpperWhiteout bool) error { + ct := createDirectory + if opts.ForSyntheticMountpoint { + ct = createSyntheticMountpoint + } + return fs.doCreateAt(ctx, rp, ct, func(parent *dentry, childName string, haveUpperWhiteout bool) error { vfsObj := fs.vfsfs.VirtualFilesystem() pop := vfs.PathOperation{ Root: parent.upperVD, @@ -722,7 +734,7 @@ func (fs *filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v // MknodAt implements vfs.FilesystemImpl.MknodAt. func (fs *filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.MknodOptions) error { - return fs.doCreateAt(ctx, rp, false /* dir */, func(parent *dentry, childName string, haveUpperWhiteout bool) error { + return fs.doCreateAt(ctx, rp, createNonDirectory, func(parent *dentry, childName string, haveUpperWhiteout bool) error { // Disallow attempts to create whiteouts. if opts.Mode&linux.S_IFMT == linux.S_IFCHR && opts.DevMajor == 0 && opts.DevMinor == 0 { return linuxerr.EPERM @@ -1476,7 +1488,7 @@ func (fs *filesystem) StatFSAt(ctx context.Context, rp *vfs.ResolvingPath) (linu // SymlinkAt implements vfs.FilesystemImpl.SymlinkAt. func (fs *filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, target string) error { - return fs.doCreateAt(ctx, rp, false /* dir */, func(parent *dentry, childName string, haveUpperWhiteout bool) error { + return fs.doCreateAt(ctx, rp, createNonDirectory, func(parent *dentry, childName string, haveUpperWhiteout bool) error { vfsObj := fs.vfsfs.VirtualFilesystem() pop := vfs.PathOperation{ Root: parent.upperVD, -- cgit v1.2.3