On Tue, Apr 8, 2025 at 5:40 PM Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote:
>
> This allows the "verity" mount option to be used with "userxattr" data-only
> layer(s).
>
> Also it allows dropping the "metacopy=on" option when the "datadir+" option
> is to be used. This cleanly separates the two features that have been
> lumped together under "metacopy=on":
>
> - data-redirect: data access is redirected to the data-only layer
>
> - meta-copy: copy up metadata only if possible
>
> Previous patches made sure that with "userxattr" metacopy only works in the
> lower -> data scenario.
>
> In this scenario the lower (metadata) layer must be secured against
> tampering, in which case the verity checksums contained in this layer can
> ensure integrity of data even in the case of an untrusted data layer.
>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/params.c | 26 ++------------------------
> 1 file changed, 2 insertions(+), 24 deletions(-)
>
> diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
> index 2468b436bb13..e297681ecac7 100644
> --- a/fs/overlayfs/params.c
> +++ b/fs/overlayfs/params.c
> @@ -871,18 +871,6 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
> config->uuid = OVL_UUID_NULL;
> }
>
> - /* Resolve verity -> metacopy dependency */
> - if (config->verity_mode && !config->metacopy) {
> - /* Don't allow explicit specified conflicting combinations */
> - if (set.metacopy) {
> - pr_err("conflicting options: metacopy=off,verity=%s\n",
> - ovl_verity_mode(config));
> - return -EINVAL;
> - }
> - /* Otherwise automatically enable metacopy. */
> - config->metacopy = true;
> - }
> -
> /*
> * This is to make the logic below simpler. It doesn't make any other
> * difference, since redirect_dir=on is only used for upper.
> @@ -890,18 +878,13 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
> if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
> config->redirect_mode = OVL_REDIRECT_ON;
>
> - /* Resolve verity -> metacopy -> redirect_dir dependency */
> + /* metacopy -> redirect_dir dependency */
> if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
> if (set.metacopy && set.redirect) {
> pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
> ovl_redirect_mode(config));
> return -EINVAL;
> }
> - if (config->verity_mode && set.redirect) {
> - pr_err("conflicting options: verity=%s,redirect_dir=%s\n",
> - ovl_verity_mode(config), ovl_redirect_mode(config));
> - return -EINVAL;
> - }
> if (set.redirect) {
> /*
> * There was an explicit redirect_dir=... that resulted
> @@ -970,7 +953,7 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
> }
>
>
> - /* Resolve userxattr -> !redirect && !metacopy && !verity dependency */
> + /* Resolve userxattr -> !redirect && !metacopy dependency */
> if (config->userxattr) {
> if (set.redirect &&
> config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
> @@ -982,11 +965,6 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
> pr_err("conflicting options: userxattr,metacopy=on\n");
> return -EINVAL;
> }
> - if (config->verity_mode) {
> - pr_err("conflicting options: userxattr,verity=%s\n",
> - ovl_verity_mode(config));
> - return -EINVAL;
> - }
> /*
> * Silently disable default setting of redirect and metacopy.
> * This shall be the default in the future as well: these
> --
> 2.49.0
>
