[PATCH v5 04/15] landlock: helper functions refactoring
Mickaël Salaün
mic at digikod.net
Mon May 16 17:14:55 UTC 2022
On 16/05/2022 17:20, Konstantin Meskhidze wrote:
> Unmask_layers(), init_layer_masks() and
> get_handled_accesses() helper functions move to
> ruleset.c and rule_type argument is added.
> This modification supports implementing new rule
> types into next landlock versions.
>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
> ---
>
> Changes since v3:
> * Splits commit.
> * Refactoring landlock_unmask_layers functions.
>
Please sort changes in antichronological order. It is easier to look at
the first lines to get the last changes.
> Changes since v4:
> * Refactoring init_layer_masks(), get_handled_accesses()
> and unmask_layers() functions to support multiple rule types.
> * Refactoring landlock_get_fs_access_mask() function with
> LANDLOCK_MASK_ACCESS_FS mask. >
> ---
> security/landlock/fs.c | 158 ++++++++----------------------------
> security/landlock/ruleset.c | 152 +++++++++++++++++++++++++++++++---
> security/landlock/ruleset.h | 17 +++-
> 3 files changed, 192 insertions(+), 135 deletions(-)
>
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index 5de24d4dd74c..3506e182b23e 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -211,60 +211,6 @@ find_rule(const struct landlock_ruleset *const domain,
> return rule;
> }
>
> -/*
> - * @layer_masks is read and may be updated according to the access request and
> - * the matching rule.
> - *
> - * Returns true if the request is allowed (i.e. relevant layer masks for the
> - * request are empty).
> - */
> -static inline bool
> -unmask_layers(const struct landlock_rule *const rule,
> - const access_mask_t access_request,
> - layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
Moving these entire blocks of code make the review/diff impossible. Why
moving these helpers?
> -{
> - size_t layer_level;
> -
> - if (!access_request || !layer_masks)
> - return true;
> - if (!rule)
> - return false;
> -
> - /*
> - * An access is granted if, for each policy layer, at least one rule
> - * encountered on the pathwalk grants the requested access,
> - * regardless of its position in the layer stack. We must then check
> - * the remaining layers for each inode, from the first added layer to
> - * the last one. When there is multiple requested accesses, for each
> - * policy layer, the full set of requested accesses may not be granted
> - * by only one rule, but by the union (binary OR) of multiple rules.
> - * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
> - */
> - for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
> - const struct landlock_layer *const layer =
> - &rule->layers[layer_level];
> - const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
> - const unsigned long access_req = access_request;
> - unsigned long access_bit;
> - bool is_empty;
> -
> - /*
> - * Records in @layer_masks which layer grants access to each
> - * requested access.
> - */
> - is_empty = true;
> - for_each_set_bit(access_bit, &access_req,
> - ARRAY_SIZE(*layer_masks)) {
> - if (layer->access & BIT_ULL(access_bit))
> - (*layer_masks)[access_bit] &= ~layer_bit;
> - is_empty = is_empty && !(*layer_masks)[access_bit];
> - }
> - if (is_empty)
> - return true;
> - }
> - return false;
> -}
> -
> /*
> * Allows access to pseudo filesystems that will never be mountable (e.g.
> * sockfs, pipefs), but can still be reachable through
> @@ -277,59 +223,6 @@ static inline bool is_nouser_or_private(const struct dentry *dentry)
> unlikely(IS_PRIVATE(d_backing_inode(dentry))));
> }
>
> -static inline access_mask_t
> -get_handled_accesses(const struct landlock_ruleset *const domain)
> -{
> - access_mask_t access_dom = 0;
> - unsigned long access_bit;
> -
> - for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS;
> - access_bit++) {
> - size_t layer_level;
> -
> - for (layer_level = 0; layer_level < domain->num_layers;
> - layer_level++) {
> - if (landlock_get_fs_access_mask(domain, layer_level) &
> - BIT_ULL(access_bit)) {
> - access_dom |= BIT_ULL(access_bit);
> - break;
> - }
> - }
> - }
> - return access_dom;
> -}
> -
> -static inline access_mask_t
> -init_layer_masks(const struct landlock_ruleset *const domain,
> - const access_mask_t access_request,
> - layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
> -{
> - access_mask_t handled_accesses = 0;
> - size_t layer_level;
> -
> - memset(layer_masks, 0, sizeof(*layer_masks));
> - /* An empty access request can happen because of O_WRONLY | O_RDWR. */
> - if (!access_request)
> - return 0;
> -
> - /* Saves all handled accesses per layer. */
> - for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
> - const unsigned long access_req = access_request;
> - unsigned long access_bit;
> -
> - for_each_set_bit(access_bit, &access_req,
> - ARRAY_SIZE(*layer_masks)) {
> - if (landlock_get_fs_access_mask(domain, layer_level) &
> - BIT_ULL(access_bit)) {
> - (*layer_masks)[access_bit] |=
> - BIT_ULL(layer_level);
> - handled_accesses |= BIT_ULL(access_bit);
> - }
> - }
> - }
> - return handled_accesses;
> -}
> -
> /*
> * Check that a destination file hierarchy has more restrictions than a source
> * file hierarchy. This is only used for link and rename actions.
> @@ -506,7 +399,8 @@ static int check_access_path_dual(
> * a superset of the meaningful requested accesses).
> */
> access_masked_parent1 = access_masked_parent2 =
> - get_handled_accesses(domain);
> + get_handled_accesses(domain, LANDLOCK_RULE_PATH_BENEATH,
> + LANDLOCK_NUM_ACCESS_FS);
> is_dom_check = true;
> } else {
> if (WARN_ON_ONCE(dentry_child1 || dentry_child2))
> @@ -519,17 +413,25 @@ static int check_access_path_dual(
>
> if (unlikely(dentry_child1)) {
> unmask_layers(find_rule(domain, dentry_child1),
> - init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
> - &_layer_masks_child1),
> - &_layer_masks_child1);
> + init_layer_masks(domain,
> + LANDLOCK_MASK_ACCESS_FS,
> + &_layer_masks_child1,
> + sizeof(_layer_masks_child1),
> + LANDLOCK_RULE_PATH_BENEATH),
> + &_layer_masks_child1,
> + ARRAY_SIZE(_layer_masks_child1));
There is a lot of formatting diff and that makes the review difficult.
Please format everything with clang-format-14.
> layer_masks_child1 = &_layer_masks_child1;
> child1_is_directory = d_is_dir(dentry_child1);
> }
> if (unlikely(dentry_child2)) {
> unmask_layers(find_rule(domain, dentry_child2),
> - init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
> - &_layer_masks_child2),
> - &_layer_masks_child2);
> + init_layer_masks(domain,
> + LANDLOCK_MASK_ACCESS_FS,
> + &_layer_masks_child2,
> + sizeof(_layer_masks_child2),
> + LANDLOCK_RULE_PATH_BENEATH),
> + &_layer_masks_child2,
> + ARRAY_SIZE(_layer_masks_child2));
> layer_masks_child2 = &_layer_masks_child2;
> child2_is_directory = d_is_dir(dentry_child2);
> }
> @@ -582,14 +484,15 @@ static int check_access_path_dual(
>
> rule = find_rule(domain, walker_path.dentry);
> allowed_parent1 = unmask_layers(rule, access_masked_parent1,
> - layer_masks_parent1);
> + layer_masks_parent1,
> + ARRAY_SIZE(*layer_masks_parent1));
> allowed_parent2 = unmask_layers(rule, access_masked_parent2,
> - layer_masks_parent2);
> + layer_masks_parent2,
> + ARRAY_SIZE(*layer_masks_parent2));
>
> /* Stops when a rule from each layer grants access. */
> if (allowed_parent1 && allowed_parent2)
> break;
> -
There is no place for such formatting/whitespace patches.
> jump_up:
> if (walker_path.dentry == walker_path.mnt->mnt_root) {
> if (follow_up(&walker_path)) {
> @@ -645,7 +548,9 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
> {
> layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
>
> - access_request = init_layer_masks(domain, access_request, &layer_masks);
> + access_request = init_layer_masks(domain, access_request,
> + &layer_masks, sizeof(layer_masks),
> + LANDLOCK_RULE_PATH_BENEATH);
> return check_access_path_dual(domain, path, access_request,
> &layer_masks, NULL, 0, NULL, NULL);
> }
> @@ -729,7 +634,8 @@ static bool collect_domain_accesses(
> return true;
>
> access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
> - layer_masks_dom);
> + layer_masks_dom, sizeof(*layer_masks_dom),
> + LANDLOCK_RULE_PATH_BENEATH);
>
> dget(dir);
> while (true) {
> @@ -737,7 +643,8 @@ static bool collect_domain_accesses(
>
> /* Gets all layers allowing all domain accesses. */
> if (unmask_layers(find_rule(domain, dir), access_dom,
> - layer_masks_dom)) {
> + layer_masks_dom,
> + ARRAY_SIZE(*layer_masks_dom))) {
> /*
> * Stops when all handled accesses are allowed by at
> * least one rule in each layer.
> @@ -851,9 +758,10 @@ static int current_check_refer_path(struct dentry *const old_dentry,
> * The LANDLOCK_ACCESS_FS_REFER access right is not required
> * for same-directory referer (i.e. no reparenting).
> */
> - access_request_parent1 = init_layer_masks(
> - dom, access_request_parent1 | access_request_parent2,
> - &layer_masks_parent1);
> + access_request_parent1 = init_layer_masks(dom,
> + access_request_parent1 | access_request_parent2,
> + &layer_masks_parent1, sizeof(layer_masks_parent1),
> + LANDLOCK_RULE_PATH_BENEATH);
> return check_access_path_dual(dom, new_dir,
> access_request_parent1,
> &layer_masks_parent1, NULL, 0,
> @@ -861,7 +769,9 @@ static int current_check_refer_path(struct dentry *const old_dentry,
> }
>
> /* Backward compatibility: no reparenting support. */
> - if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER))
> + if (!(get_handled_accesses(dom, LANDLOCK_RULE_PATH_BENEATH,
> + LANDLOCK_NUM_ACCESS_FS) &
> + LANDLOCK_ACCESS_FS_REFER))
> return -EXDEV;
>
> access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> index 4b4c9953bb32..c4ed783d655b 100644
> --- a/security/landlock/ruleset.c
> +++ b/security/landlock/ruleset.c
> @@ -233,7 +233,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
> &(*layers)[0]);
> if (IS_ERR(new_rule))
> return PTR_ERR(new_rule);
> - rb_replace_node(&this->node, &new_rule->node, &ruleset->root_inode);
> + rb_replace_node(&this->node, &new_rule->node,
> + &ruleset->root_inode);
This is a pure formatting hunk. :/
> free_rule(this, rule_type);
> break;
> }
> @@ -246,7 +247,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
> return -E2BIG;
> switch (rule_type) {
> case LANDLOCK_RULE_PATH_BENEATH:
> - new_rule = create_rule(object_ptr, 0, layers, num_layers, NULL);
> + new_rule = create_rule(object_ptr, 0, layers,
> + num_layers, NULL);
> if (IS_ERR(new_rule))
> return PTR_ERR(new_rule);
> rb_link_node(&new_rule->node, parent_node, walker_node);
> @@ -281,8 +283,8 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
> } };
>
> build_check_layer();
> - return insert_rule(ruleset, object_ptr, object_data, rule_type, &layers,
> - ARRAY_SIZE(layers));
> + return insert_rule(ruleset, object_ptr, object_data, rule_type,
> + &layers, ARRAY_SIZE(layers));
> }
>
> static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
> @@ -335,8 +337,9 @@ static int tree_merge(struct landlock_ruleset *const src,
>
> switch (rule_type) {
> case LANDLOCK_RULE_PATH_BENEATH:
> - err = insert_rule(dst, walker_rule->object.ptr, 0, rule_type,
> - &layers, ARRAY_SIZE(layers));
> + err = insert_rule(dst, walker_rule->object.ptr, 0,
> + rule_type, &layers,
> + ARRAY_SIZE(layers));
> break;
> }
> if (err)
> @@ -433,9 +436,13 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
> err = -EINVAL;
> goto out_unlock;
> }
> - /* Copies the parent layer stack and leaves a space for the new layer. */
> + /*
> + * Copies the parent layer stack and leaves a space
> + * for the new layer.
> + */
> memcpy(child->access_masks, parent->access_masks,
> - flex_array_size(parent, access_masks, parent->num_layers));
> + flex_array_size(parent, access_masks,
> + parent->num_layers));
>
> if (WARN_ON_ONCE(!parent->hierarchy)) {
> err = -EINVAL;
> @@ -455,8 +462,9 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
> struct landlock_rule *freeme, *next;
>
> might_sleep();
> - rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
> - node)
> + rbtree_postorder_for_each_entry_safe(freeme, next,
> + &ruleset->root_inode,
> + node)
> free_rule(freeme, LANDLOCK_RULE_PATH_BENEATH);
> put_hierarchy(ruleset->hierarchy);
> kfree(ruleset);
> @@ -577,3 +585,127 @@ const struct landlock_rule *landlock_find_rule(
> }
> return NULL;
> }
> +
> +access_mask_t get_handled_accesses(
> + const struct landlock_ruleset *const domain,
> + u16 rule_type, u16 num_access)
> +{
> + access_mask_t access_dom = 0;
> + unsigned long access_bit;
> +
> + switch (rule_type) {
> + case LANDLOCK_RULE_PATH_BENEATH:
> + for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS;
> + access_bit++) {
> + size_t layer_level;
> +
> + for (layer_level = 0; layer_level < domain->num_layers;
> + layer_level++) {
> + if (landlock_get_fs_access_mask(domain,
> + layer_level) &
> + BIT_ULL(access_bit)) {
> + access_dom |= BIT_ULL(access_bit);
> + break;
> + }
> + }
> + }
> + break;
> + default:
> + break;
> + }
> + return access_dom;
> +}
> +
> +/*
> + * @layer_masks is read and may be updated according to the access request and
> + * the matching rule.
> + *
> + * Returns true if the request is allowed (i.e. relevant layer masks for the
> + * request are empty).
> + */
> +bool unmask_layers(const struct landlock_rule *const rule,
> + const access_mask_t access_request,
> + layer_mask_t (*const layer_masks)[], size_t masks_array_size)
> +{
> + size_t layer_level;
> +
> + if (!access_request || !layer_masks)
> + return true;
> + if (!rule)
> + return false;
> +
> + /*
> + * An access is granted if, for each policy layer, at least one rule
> + * encountered on the pathwalk grants the requested access,
> + * regardless of its position in the layer stack. We must then check
> + * the remaining layers for each inode, from the first added layer to
> + * the last one. When there is multiple requested accesses, for each
> + * policy layer, the full set of requested accesses may not be granted
> + * by only one rule, but by the union (binary OR) of multiple rules.
> + * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
> + */
> + for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
> + const struct landlock_layer *const layer =
> + &rule->layers[layer_level];
> + const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
> + const unsigned long access_req = access_request;
> + unsigned long access_bit;
> + bool is_empty;
> +
> + /*
> + * Records in @layer_masks which layer grants access to each
> + * requested access.
> + */
> + is_empty = true;
> + for_each_set_bit(access_bit, &access_req, masks_array_size) {
> + if (layer->access & BIT_ULL(access_bit))
> + (*layer_masks)[access_bit] &= ~layer_bit;
> + is_empty = is_empty && !(*layer_masks)[access_bit];
> + }
> + if (is_empty)
> + return true;
> + }
> + return false;
> +}
> +
> +access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
> + const access_mask_t access_request,
> + layer_mask_t (*const layer_masks)[],
> + size_t masks_size,
> + u16 rule_type)
> +{
> + access_mask_t handled_accesses = 0;
> + size_t layer_level;
> +
> + memset(layer_masks, 0, masks_size);
> +
> + /* An empty access request can happen because of O_WRONLY | O_RDWR. */
> + if (!access_request)
> + return 0;
> +
> + /* Saves all handled accesses per layer. */
> + for (layer_level = 0; layer_level < domain->num_layers;
> + layer_level++) {
> + const unsigned long access_req = access_request;
> + unsigned long access_bit;
> +
> + switch (rule_type) {
> + case LANDLOCK_RULE_PATH_BENEATH:
> + for_each_set_bit(access_bit, &access_req,
> + LANDLOCK_NUM_ACCESS_FS) {
> + if (landlock_get_fs_access_mask(domain,
> + layer_level) &
> + BIT_ULL(access_bit)) {
> + (*layer_masks)[access_bit] |=
> + BIT_ULL(layer_level);
> + handled_accesses |=
> + BIT_ULL(access_bit);
> + }
> + }
> + break;
> + default:
> + return 0;
> + }
> + }
> + return handled_accesses;
> +}
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index 3066e5d7180c..f3cd890d0348 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -195,7 +195,22 @@ static inline u32 landlock_get_fs_access_mask(
> const struct landlock_ruleset *ruleset,
> u16 mask_level)
> {
> - return ruleset->access_masks[mask_level];
> + return (ruleset->access_masks[mask_level] & LANDLOCK_MASK_ACCESS_FS);
> }
>
> +access_mask_t get_handled_accesses(
> + const struct landlock_ruleset *const domain,
> + u16 rule_type, u16 num_access);
> +
> +bool unmask_layers(const struct landlock_rule *const rule,
> + const access_mask_t access_request,
> + layer_mask_t (*const layer_masks)[],
> + size_t masks_array_size);
> +
> +access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
> + const access_mask_t access_request,
> + layer_mask_t (*const layer_masks)[],
> + size_t masks_size,
> + u16 rule_type);
These declarations are useless.
> +
> #endif /* _SECURITY_LANDLOCK_RULESET_H */
> --
> 2.25.1
>
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