diff options
Diffstat (limited to 'pkg/sentry/fsimpl/overlay')
| -rw-r--r-- | pkg/sentry/fsimpl/overlay/copy_up.go | 52 | ||||
| -rw-r--r-- | pkg/sentry/fsimpl/overlay/filesystem.go | 120 | ||||
| -rw-r--r-- | pkg/sentry/fsimpl/overlay/overlay.go | 36 |
3 files changed, 192 insertions, 16 deletions
diff --git a/pkg/sentry/fsimpl/overlay/copy_up.go b/pkg/sentry/fsimpl/overlay/copy_up.go index 13735eb05..ba7b8495a 100644 --- a/pkg/sentry/fsimpl/overlay/copy_up.go +++ b/pkg/sentry/fsimpl/overlay/copy_up.go @@ -91,6 +91,10 @@ func (d *dentry) copyUpLocked(ctx context.Context) error { if err != nil { ctx.Warningf("Unrecoverable overlayfs inconsistency: failed to delete upper layer file after copy-up error: %v", err) } + if d.upperVD.Ok() { + d.upperVD.DecRef(ctx) + d.upperVD = vfs.VirtualDentry{} + } } switch ftype { case linux.S_IFREG: @@ -234,7 +238,10 @@ func (d *dentry) copyUpLocked(ctx context.Context) error { panic(fmt.Sprintf("unexpected file type %o", ftype)) } - // TODO(gvisor.dev/issue/1199): copy up xattrs + if err := d.copyXattrsLocked(ctx); err != nil { + cleanupUndoCopyUp() + return err + } // Update the dentry's device and inode numbers (except for directories, // for which these remain overlay-assigned). @@ -246,14 +253,10 @@ func (d *dentry) copyUpLocked(ctx context.Context) error { Mask: linux.STATX_INO, }) if err != nil { - d.upperVD.DecRef(ctx) - d.upperVD = vfs.VirtualDentry{} cleanupUndoCopyUp() return err } if upperStat.Mask&linux.STATX_INO == 0 { - d.upperVD.DecRef(ctx) - d.upperVD = vfs.VirtualDentry{} cleanupUndoCopyUp() return syserror.EREMOTE } @@ -265,3 +268,42 @@ func (d *dentry) copyUpLocked(ctx context.Context) error { atomic.StoreUint32(&d.copiedUp, 1) return nil } + +// copyXattrsLocked copies a subset of lower's extended attributes to upper. +// Attributes that configure an overlay in the lower are not copied up. +// +// Preconditions: d.copyMu must be locked for writing. +func (d *dentry) copyXattrsLocked(ctx context.Context) error { + vfsObj := d.fs.vfsfs.VirtualFilesystem() + lowerPop := &vfs.PathOperation{Root: d.lowerVDs[0], Start: d.lowerVDs[0]} + upperPop := &vfs.PathOperation{Root: d.upperVD, Start: d.upperVD} + + lowerXattrs, err := vfsObj.ListxattrAt(ctx, d.fs.creds, lowerPop, 0) + if err != nil { + if err == syserror.EOPNOTSUPP { + // There are no guarantees as to the contents of lowerXattrs. + return nil + } + ctx.Warningf("failed to copy up xattrs because ListxattrAt failed: %v", err) + return err + } + + for _, name := range lowerXattrs { + // Do not copy up overlay attributes. + if isOverlayXattr(name) { + continue + } + + value, err := vfsObj.GetxattrAt(ctx, d.fs.creds, lowerPop, &vfs.GetxattrOptions{Name: name, Size: 0}) + if err != nil { + ctx.Warningf("failed to copy up xattrs because GetxattrAt failed: %v", err) + return err + } + + if err := vfsObj.SetxattrAt(ctx, d.fs.creds, upperPop, &vfs.SetxattrOptions{Name: name, Value: value}); err != nil { + ctx.Warningf("failed to copy up xattrs because SetxattrAt failed: %v", err) + return err + } + } + return nil +} diff --git a/pkg/sentry/fsimpl/overlay/filesystem.go b/pkg/sentry/fsimpl/overlay/filesystem.go index 63df86481..46528c99c 100644 --- a/pkg/sentry/fsimpl/overlay/filesystem.go +++ b/pkg/sentry/fsimpl/overlay/filesystem.go @@ -15,6 +15,7 @@ package overlay import ( + "strings" "sync/atomic" "gvisor.dev/gvisor/pkg/abi/linux" @@ -27,10 +28,15 @@ import ( "gvisor.dev/gvisor/pkg/syserror" ) +// _OVL_XATTR_PREFIX is an extended attribute key prefix to identify overlayfs +// attributes. +// Linux: fs/overlayfs/overlayfs.h:OVL_XATTR_PREFIX +const _OVL_XATTR_PREFIX = linux.XATTR_TRUSTED_PREFIX + "overlay." + // _OVL_XATTR_OPAQUE is an extended attribute key whose value is set to "y" for // opaque directories. // Linux: fs/overlayfs/overlayfs.h:OVL_XATTR_OPAQUE -const _OVL_XATTR_OPAQUE = linux.XATTR_TRUSTED_PREFIX + "overlay.opaque" +const _OVL_XATTR_OPAQUE = _OVL_XATTR_PREFIX + "opaque" func isWhiteout(stat *linux.Statx) bool { return stat.Mode&linux.S_IFMT == linux.S_IFCHR && stat.RdevMajor == 0 && stat.RdevMinor == 0 @@ -1347,18 +1353,42 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error return nil } +// isOverlayXattr returns whether the given extended attribute configures the +// overlay. +func isOverlayXattr(name string) bool { + return strings.HasPrefix(name, _OVL_XATTR_PREFIX) +} + // ListxattrAt implements vfs.FilesystemImpl.ListxattrAt. func (fs *filesystem) ListxattrAt(ctx context.Context, rp *vfs.ResolvingPath, size uint64) ([]string, error) { var ds *[]*dentry fs.renameMu.RLock() defer fs.renameMuRUnlockAndCheckDrop(ctx, &ds) - _, err := fs.resolveLocked(ctx, rp, &ds) + d, err := fs.resolveLocked(ctx, rp, &ds) if err != nil { return nil, err } - // TODO(gvisor.dev/issue/1199): Linux overlayfs actually allows listxattr, - // but not any other xattr syscalls. For now we just reject all of them. - return nil, syserror.ENOTSUP + + return fs.listXattr(ctx, d, size) +} + +func (fs *filesystem) listXattr(ctx context.Context, d *dentry, size uint64) ([]string, error) { + vfsObj := d.fs.vfsfs.VirtualFilesystem() + top := d.topLayer() + names, err := vfsObj.ListxattrAt(ctx, fs.creds, &vfs.PathOperation{Root: top, Start: top}, size) + if err != nil { + return nil, err + } + + // Filter out all overlay attributes. + n := 0 + for _, name := range names { + if !isOverlayXattr(name) { + names[n] = name + n++ + } + } + return names[:n], err } // GetxattrAt implements vfs.FilesystemImpl.GetxattrAt. @@ -1366,11 +1396,29 @@ func (fs *filesystem) GetxattrAt(ctx context.Context, rp *vfs.ResolvingPath, opt var ds *[]*dentry fs.renameMu.RLock() defer fs.renameMuRUnlockAndCheckDrop(ctx, &ds) - _, err := fs.resolveLocked(ctx, rp, &ds) + d, err := fs.resolveLocked(ctx, rp, &ds) if err != nil { return "", err } - return "", syserror.ENOTSUP + + return fs.getXattr(ctx, d, rp.Credentials(), &opts) +} + +func (fs *filesystem) getXattr(ctx context.Context, d *dentry, creds *auth.Credentials, opts *vfs.GetxattrOptions) (string, error) { + if err := d.checkXattrPermissions(creds, opts.Name, vfs.MayRead); err != nil { + return "", err + } + + // Return EOPNOTSUPP when fetching an overlay attribute. + // See fs/overlayfs/super.c:ovl_own_xattr_get(). + if isOverlayXattr(opts.Name) { + return "", syserror.EOPNOTSUPP + } + + // Analogous to fs/overlayfs/super.c:ovl_other_xattr_get(). + vfsObj := d.fs.vfsfs.VirtualFilesystem() + top := d.topLayer() + return vfsObj.GetxattrAt(ctx, fs.creds, &vfs.PathOperation{Root: top, Start: top}, opts) } // SetxattrAt implements vfs.FilesystemImpl.SetxattrAt. @@ -1378,11 +1426,36 @@ func (fs *filesystem) SetxattrAt(ctx context.Context, rp *vfs.ResolvingPath, opt var ds *[]*dentry fs.renameMu.RLock() defer fs.renameMuRUnlockAndCheckDrop(ctx, &ds) - _, err := fs.resolveLocked(ctx, rp, &ds) + d, err := fs.resolveLocked(ctx, rp, &ds) if err != nil { return err } - return syserror.ENOTSUP + + return fs.setXattrLocked(ctx, d, rp.Mount(), rp.Credentials(), &opts) +} + +// Precondition: fs.renameMu must be locked. +func (fs *filesystem) setXattrLocked(ctx context.Context, d *dentry, mnt *vfs.Mount, creds *auth.Credentials, opts *vfs.SetxattrOptions) error { + if err := d.checkXattrPermissions(creds, opts.Name, vfs.MayWrite); err != nil { + return err + } + + // Return EOPNOTSUPP when setting an overlay attribute. + // See fs/overlayfs/super.c:ovl_own_xattr_set(). + if isOverlayXattr(opts.Name) { + return syserror.EOPNOTSUPP + } + + // Analogous to fs/overlayfs/super.c:ovl_other_xattr_set(). + if err := mnt.CheckBeginWrite(); err != nil { + return err + } + defer mnt.EndWrite() + if err := d.copyUpLocked(ctx); err != nil { + return err + } + vfsObj := d.fs.vfsfs.VirtualFilesystem() + return vfsObj.SetxattrAt(ctx, fs.creds, &vfs.PathOperation{Root: d.upperVD, Start: d.upperVD}, opts) } // RemovexattrAt implements vfs.FilesystemImpl.RemovexattrAt. @@ -1390,11 +1463,36 @@ func (fs *filesystem) RemovexattrAt(ctx context.Context, rp *vfs.ResolvingPath, var ds *[]*dentry fs.renameMu.RLock() defer fs.renameMuRUnlockAndCheckDrop(ctx, &ds) - _, err := fs.resolveLocked(ctx, rp, &ds) + d, err := fs.resolveLocked(ctx, rp, &ds) if err != nil { return err } - return syserror.ENOTSUP + + return fs.removeXattrLocked(ctx, d, rp.Mount(), rp.Credentials(), name) +} + +// Precondition: fs.renameMu must be locked. +func (fs *filesystem) removeXattrLocked(ctx context.Context, d *dentry, mnt *vfs.Mount, creds *auth.Credentials, name string) error { + if err := d.checkXattrPermissions(creds, name, vfs.MayWrite); err != nil { + return err + } + + // Like SetxattrAt, return EOPNOTSUPP when removing an overlay attribute. + // Linux passes the remove request to xattr_handler->set. + // See fs/xattr.c:vfs_removexattr(). + if isOverlayXattr(name) { + return syserror.EOPNOTSUPP + } + + if err := mnt.CheckBeginWrite(); err != nil { + return err + } + defer mnt.EndWrite() + if err := d.copyUpLocked(ctx); err != nil { + return err + } + vfsObj := d.fs.vfsfs.VirtualFilesystem() + return vfsObj.RemovexattrAt(ctx, fs.creds, &vfs.PathOperation{Root: d.upperVD, Start: d.upperVD}, name) } // PrependPath implements vfs.FilesystemImpl.PrependPath. diff --git a/pkg/sentry/fsimpl/overlay/overlay.go b/pkg/sentry/fsimpl/overlay/overlay.go index 00562667f..e706f9d4e 100644 --- a/pkg/sentry/fsimpl/overlay/overlay.go +++ b/pkg/sentry/fsimpl/overlay/overlay.go @@ -570,6 +570,16 @@ func (d *dentry) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes) return vfs.GenericCheckPermissions(creds, ats, linux.FileMode(atomic.LoadUint32(&d.mode)), auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))) } +func (d *dentry) checkXattrPermissions(creds *auth.Credentials, name string, ats vfs.AccessTypes) error { + mode := linux.FileMode(atomic.LoadUint32(&d.mode)) + kuid := auth.KUID(atomic.LoadUint32(&d.uid)) + kgid := auth.KGID(atomic.LoadUint32(&d.gid)) + if err := vfs.GenericCheckPermissions(creds, ats, mode, kuid, kgid); err != nil { + return err + } + return vfs.CheckXattrPermissions(creds, ats, mode, kuid, name) +} + // statInternalMask is the set of stat fields that is set by // dentry.statInternalTo(). const statInternalMask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_UID | linux.STATX_GID | linux.STATX_INO @@ -622,6 +632,32 @@ func (fd *fileDescription) dentry() *dentry { return fd.vfsfd.Dentry().Impl().(*dentry) } +// Listxattr implements vfs.FileDescriptionImpl.Listxattr. +func (fd *fileDescription) Listxattr(ctx context.Context, size uint64) ([]string, error) { + return fd.filesystem().listXattr(ctx, fd.dentry(), size) +} + +// Getxattr implements vfs.FileDescriptionImpl.Getxattr. +func (fd *fileDescription) Getxattr(ctx context.Context, opts vfs.GetxattrOptions) (string, error) { + return fd.filesystem().getXattr(ctx, fd.dentry(), auth.CredentialsFromContext(ctx), &opts) +} + +// Setxattr implements vfs.FileDescriptionImpl.Setxattr. +func (fd *fileDescription) Setxattr(ctx context.Context, opts vfs.SetxattrOptions) error { + fs := fd.filesystem() + fs.renameMu.RLock() + defer fs.renameMu.RUnlock() + return fs.setXattrLocked(ctx, fd.dentry(), fd.vfsfd.Mount(), auth.CredentialsFromContext(ctx), &opts) +} + +// Removexattr implements vfs.FileDescriptionImpl.Removexattr. +func (fd *fileDescription) Removexattr(ctx context.Context, name string) error { + fs := fd.filesystem() + fs.renameMu.RLock() + defer fs.renameMu.RUnlock() + return fs.removeXattrLocked(ctx, fd.dentry(), fd.vfsfd.Mount(), auth.CredentialsFromContext(ctx), name) +} + // LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX. func (fd *fileDescription) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, start, length uint64, whence int16, block fslock.Blocker) error { return fd.Locks().LockPOSIX(ctx, &fd.vfsfd, uid, t, start, length, whence, block) |