From 10f2c8db915df14102e3f4d9efcfce372c90707a Mon Sep 17 00:00:00 2001 From: Nicolas Lacasse Date: Fri, 27 Mar 2020 16:53:28 -0700 Subject: Add FilesystemType.Name method, and FilesystemType field to Filesystem struct. Both have analogues in Linux: * struct file_system_type has a char *name field. * struct super_block keeps a pointer to the file_system_type. These fields are necessary to support the `filesystem type` field in /proc/[pid]/mountinfo. PiperOrigin-RevId: 303434063 --- pkg/sentry/vfs/anonfs.go | 13 +++++++++++++ pkg/sentry/vfs/filesystem.go | 11 ++++++++++- pkg/sentry/vfs/filesystem_type.go | 3 +++ pkg/sentry/vfs/vfs.go | 2 +- 4 files changed, 27 insertions(+), 2 deletions(-) (limited to 'pkg/sentry/vfs') diff --git a/pkg/sentry/vfs/anonfs.go b/pkg/sentry/vfs/anonfs.go index f58867066..d1f6dfb45 100644 --- a/pkg/sentry/vfs/anonfs.go +++ b/pkg/sentry/vfs/anonfs.go @@ -51,6 +51,19 @@ const ( anonFileGID = auth.RootKGID ) +// anonFilesystemType implements FilesystemType. +type anonFilesystemType struct{} + +// GetFilesystem implements FilesystemType.GetFilesystem. +func (anonFilesystemType) GetFilesystem(context.Context, *VirtualFilesystem, *auth.Credentials, string, GetFilesystemOptions) (*Filesystem, *Dentry, error) { + panic("cannot instaniate an anon filesystem") +} + +// Name implemenents FilesystemType.Name. +func (anonFilesystemType) Name() string { + return "none" +} + // anonFilesystem is the implementation of FilesystemImpl that backs // VirtualDentries returned by VirtualFilesystem.NewAnonVirtualDentry(). // diff --git a/pkg/sentry/vfs/filesystem.go b/pkg/sentry/vfs/filesystem.go index 7b7d233f9..cd34782ff 100644 --- a/pkg/sentry/vfs/filesystem.go +++ b/pkg/sentry/vfs/filesystem.go @@ -42,21 +42,30 @@ type Filesystem struct { // immutable. vfs *VirtualFilesystem + // fsType is the FilesystemType of this Filesystem. + fsType FilesystemType + // impl is the FilesystemImpl associated with this Filesystem. impl is // immutable. This should be the last field in Dentry. impl FilesystemImpl } // Init must be called before first use of fs. -func (fs *Filesystem) Init(vfsObj *VirtualFilesystem, impl FilesystemImpl) { +func (fs *Filesystem) Init(vfsObj *VirtualFilesystem, fsType FilesystemType, impl FilesystemImpl) { fs.refs = 1 fs.vfs = vfsObj + fs.fsType = fsType fs.impl = impl vfsObj.filesystemsMu.Lock() vfsObj.filesystems[fs] = struct{}{} vfsObj.filesystemsMu.Unlock() } +// FilesystemType returns the FilesystemType for this Filesystem. +func (fs *Filesystem) FilesystemType() FilesystemType { + return fs.fsType +} + // VirtualFilesystem returns the containing VirtualFilesystem. func (fs *Filesystem) VirtualFilesystem() *VirtualFilesystem { return fs.vfs diff --git a/pkg/sentry/vfs/filesystem_type.go b/pkg/sentry/vfs/filesystem_type.go index bb9cada81..f2298f7f6 100644 --- a/pkg/sentry/vfs/filesystem_type.go +++ b/pkg/sentry/vfs/filesystem_type.go @@ -30,6 +30,9 @@ type FilesystemType interface { // along with its mount root. A reference is taken on the returned // Filesystem and Dentry. GetFilesystem(ctx context.Context, vfsObj *VirtualFilesystem, creds *auth.Credentials, source string, opts GetFilesystemOptions) (*Filesystem, *Dentry, error) + + // Name returns the name of this FilesystemType. + Name() string } // GetFilesystemOptions contains options to FilesystemType.GetFilesystem. diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go index 1708c1a53..720b90d8f 100644 --- a/pkg/sentry/vfs/vfs.go +++ b/pkg/sentry/vfs/vfs.go @@ -134,7 +134,7 @@ func (vfs *VirtualFilesystem) Init() error { anonfs := anonFilesystem{ devMinor: anonfsDevMinor, } - anonfs.vfsfs.Init(vfs, &anonfs) + anonfs.vfsfs.Init(vfs, &anonFilesystemType{}, &anonfs) defer anonfs.vfsfs.DecRef() anonMount, err := vfs.NewDisconnectedMount(&anonfs.vfsfs, nil, &MountOptions{}) if err != nil { -- cgit v1.2.3 From f6e4daa67ad5f07ac1bcff33476b4d13f49a69bc Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Fri, 27 Mar 2020 16:54:45 -0700 Subject: Add vfs.PathnameReachable(). /proc/[pid]/mount* omit mounts whose mount point is outside the chroot, which is checked (indirectly) via __d_path(). PiperOrigin-RevId: 303434226 --- pkg/sentry/vfs/pathname.go | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) (limited to 'pkg/sentry/vfs') diff --git a/pkg/sentry/vfs/pathname.go b/pkg/sentry/vfs/pathname.go index b318c681a..f21a88034 100644 --- a/pkg/sentry/vfs/pathname.go +++ b/pkg/sentry/vfs/pathname.go @@ -90,6 +90,49 @@ loop: return b.String(), nil } +// PathnameReachable returns an absolute pathname to vd, consistent with +// Linux's __d_path() (as used by seq_path_root()). If vfsroot.Ok() and vd is +// not reachable from vfsroot, such that seq_path_root() would return SEQ_SKIP +// (causing the entire containing entry to be skipped), PathnameReachable +// returns ("", nil). +func (vfs *VirtualFilesystem) PathnameReachable(ctx context.Context, vfsroot, vd VirtualDentry) (string, error) { + b := getFSPathBuilder() + defer putFSPathBuilder(b) + haveRef := false + defer func() { + if haveRef { + vd.DecRef() + } + }() +loop: + for { + err := vd.mount.fs.impl.PrependPath(ctx, vfsroot, vd, b) + switch err.(type) { + case nil: + if vd.mount == vfsroot.mount && vd.mount.root == vfsroot.dentry { + break loop + } + nextVD := vfs.getMountpointAt(vd.mount, vfsroot) + if !nextVD.Ok() { + return "", nil + } + if haveRef { + vd.DecRef() + } + vd = nextVD + haveRef = true + case PrependPathAtVFSRootError: + break loop + case PrependPathAtNonMountRootError, PrependPathSyntheticError: + return "", nil + default: + return "", err + } + } + b.PrependByte('/') + return b.String(), nil +} + // PathnameForGetcwd returns an absolute pathname to vd, consistent with // Linux's sys_getcwd(). func (vfs *VirtualFilesystem) PathnameForGetcwd(ctx context.Context, vfsroot, vd VirtualDentry) (string, error) { -- cgit v1.2.3