diff options
Diffstat (limited to 'pkg/sentry/fsimpl/overlay/filesystem.go')
| -rw-r--r-- | pkg/sentry/fsimpl/overlay/filesystem.go | 120 |
1 files changed, 109 insertions, 11 deletions
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. |