On Wed, Jan 08, 2025 at 04:43:19PM +0100, Mickaël Salaün wrote:
> Fix a logical issue that could have been visible if the source or the
> destination of a rename/link action was allowed for either the source or
> the destination but not both. However, this logical bug is unreachable
> because either:
> - the rename/link action is allowed by the access rights tied to the
> same mount point (without relying on access rights in a parent mount
> point) and the access request is allowed (i.e. allow_parent1 and
> allow_parent2 are true in current_check_refer_path),
> - or a common rule in a parent mount point updates the access check for
> the source and the destination (cf. is_access_to_paths_allowed).
>
> See the following layout1.refer_part_mount_tree_is_allowed test that
> work with and without this fix.
>
> This fix does not impact current code but it is required for the audit
> support.
>
> Cc: Günther Noack <[email protected]>
> Signed-off-by: Mickaël Salaün <[email protected]>
> Link: https://lore.kernel.org/r/[email protected]
Pushed in my next tree to simplify next patch series.
> ---
>
> Changes since v2:
> - New patch.
> ---
> security/landlock/fs.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index 171012efb559..ddadc465581e 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -567,6 +567,12 @@ static void test_no_more_access(struct kunit *const test)
> #undef NMA_TRUE
> #undef NMA_FALSE
>
> +static bool is_layer_masks_allowed(
> + layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
> +{
> + return !memchr_inv(layer_masks, 0, sizeof(*layer_masks));
> +}
> +
> /*
> * Removes @layer_masks accesses that are not requested.
> *
> @@ -584,7 +590,8 @@ scope_to_request(const access_mask_t access_request,
>
> for_each_clear_bit(access_bit, &access_req, ARRAY_SIZE(*layer_masks))
> (*layer_masks)[access_bit] = 0;
> - return !memchr_inv(layer_masks, 0, sizeof(*layer_masks));
> +
> + return is_layer_masks_allowed(layer_masks);
> }
>
> #ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST
> @@ -773,9 +780,14 @@ static bool is_access_to_paths_allowed(
> if (WARN_ON_ONCE(domain->num_layers < 1 || !layer_masks_parent1))
> return false;
>
> + allowed_parent1 = is_layer_masks_allowed(layer_masks_parent1);
> +
> if (unlikely(layer_masks_parent2)) {
> if (WARN_ON_ONCE(!dentry_child1))
> return false;
> +
> + allowed_parent2 = is_layer_masks_allowed(layer_masks_parent2);
> +
> /*
> * For a double request, first check for potential privilege
> * escalation by looking at domain handled accesses (which are
> --
> 2.47.1
>
>
