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Date: Thu, 17 Nov 2022 19:42:24 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc: willemdebruijn.kernel@...il.com, gnoack3000@...il.com,
linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, artem.kuzin@...wei.com
Subject: Re: [PATCH v8 05/12] landlock: Refactor unmask_layers() and
init_layer_masks()
On 21/10/2022 17:26, Konstantin Meskhidze wrote:
> Adds new key_type argument to init_layer_masks() helper.
Add a new key_type argument to the…
> Adds masks_array_size argument to unmask_layers() helper.
Add a masks_array_size argument to the…
The name of these helpers need to be prefixed with "landlock_".
> These modifications support implementing new rule types in the next
> Landlock versions.
>
> Co-developed-by: Mickaël Salaün <mic@...ikod.net>
Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---
>
> Changes since v7:
> * Refactors commit message, adds a co-developer.
> * Minor fixes.
>
> Changes since v6:
> * Removes masks_size attribute from init_layer_masks().
> * Refactors init_layer_masks() with new landlock_key_type.
>
> Changes since v5:
> * Splits commit.
> * Formats code with clang-format-14.
>
> Changes since v4:
> * Refactors init_layer_masks(), get_handled_accesses()
> and unmask_layers() functions to support multiple rule types.
> * Refactors landlock_get_fs_access_mask() function with
> LANDLOCK_MASK_ACCESS_FS mask.
>
> Changes since v3:
> * Splits commit.
> * Refactors landlock_unmask_layers functions.
>
> ---
> security/landlock/fs.c | 36 ++++++++++++++++++-------------
> security/landlock/ruleset.c | 42 ++++++++++++++++++++++++++-----------
> security/landlock/ruleset.h | 11 +++++-----
> 3 files changed, 58 insertions(+), 31 deletions(-)
>
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index 240e42a8f788..fe76a11483f8 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -435,16 +435,20 @@ static bool is_access_to_paths_allowed(
> 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);
> + &_layer_masks_child1,
> + LANDLOCK_KEY_INODE),
> + &_layer_masks_child1,
> + ARRAY_SIZE(_layer_masks_child1));
> 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);
> + &_layer_masks_child2,
> + LANDLOCK_KEY_INODE),
> + &_layer_masks_child2,
> + ARRAY_SIZE(_layer_masks_child2));
> layer_masks_child2 = &_layer_masks_child2;
> child2_is_directory = d_is_dir(dentry_child2);
> }
> @@ -496,15 +500,16 @@ static bool is_access_to_paths_allowed(
> }
>
> rule = find_rule(domain, walker_path.dentry);
> - allowed_parent1 = unmask_layers(rule, access_masked_parent1,
> - layer_masks_parent1);
> - allowed_parent2 = unmask_layers(rule, access_masked_parent2,
> - layer_masks_parent2);
> + allowed_parent1 = unmask_layers(
> + rule, access_masked_parent1, layer_masks_parent1,
> + ARRAY_SIZE(*layer_masks_parent1));
> + allowed_parent2 = unmask_layers(
> + rule, access_masked_parent2, layer_masks_parent2,
> + ARRAY_SIZE(*layer_masks_parent2));
>
> /* Stops when a rule from each layer grants access. */
> if (allowed_parent1 && allowed_parent2)
> break;
> -
> jump_up:
> if (walker_path.dentry == walker_path.mnt->mnt_root) {
> if (follow_up(&walker_path)) {
> @@ -543,7 +548,8 @@ 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,
> + LANDLOCK_KEY_INODE);
> if (is_access_to_paths_allowed(domain, path, access_request,
> &layer_masks, NULL, 0, NULL, NULL))
> return 0;
> @@ -630,7 +636,7 @@ static bool collect_domain_accesses(
> return true;
>
> access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
> - layer_masks_dom);
> + layer_masks_dom, LANDLOCK_KEY_INODE);
>
> dget(dir);
> while (true) {
> @@ -638,7 +644,8 @@ 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.
> @@ -754,7 +761,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
> */
> access_request_parent1 = init_layer_masks(
> dom, access_request_parent1 | access_request_parent2,
> - &layer_masks_parent1);
> + &layer_masks_parent1, LANDLOCK_KEY_INODE);
> if (is_access_to_paths_allowed(
> dom, new_dir, access_request_parent1,
> &layer_masks_parent1, NULL, 0, NULL, NULL))
> @@ -1131,7 +1138,8 @@ static int hook_file_open(struct file *const file)
>
> if (is_access_to_paths_allowed(
> dom, &file->f_path,
> - init_layer_masks(dom, full_access_request, &layer_masks),
> + init_layer_masks(dom, full_access_request, &layer_masks,
> + LANDLOCK_KEY_INODE),
> &layer_masks, NULL, 0, NULL, NULL)) {
> allowed_access = full_access_request;
> } else {
> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> index 02ab14439c43..c7cf54ba4f6d 100644
> --- a/security/landlock/ruleset.c
> +++ b/security/landlock/ruleset.c
> @@ -576,13 +576,15 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
> /*
> * @layer_masks is read and may be updated according to the access request and
> * the matching rule.
> + * @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
> *
> * 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)[LANDLOCK_NUM_ACCESS_FS])
> + layer_mask_t (*const layer_masks)[],
> + const size_t masks_array_size)
> {
> size_t layer_level;
>
> @@ -614,8 +616,7 @@ bool unmask_layers(const struct landlock_rule *const rule,
> * requested access.
> */
> is_empty = true;
> - for_each_set_bit(access_bit, &access_req,
> - ARRAY_SIZE(*layer_masks)) {
> + 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];
> @@ -626,6 +627,10 @@ bool unmask_layers(const struct landlock_rule *const rule,
> return false;
> }
>
> +typedef access_mask_t
> +get_access_mask_t(const struct landlock_ruleset *const ruleset,
> + const u16 layer_level);
> +
> /**
> * init_layer_masks - Initialize layer masks from an access request
> *
> @@ -635,19 +640,33 @@ bool unmask_layers(const struct landlock_rule *const rule,
> * @domain: The domain that defines the current restrictions.
> * @access_request: The requested access rights to check.
> * @layer_masks: The layer masks to populate.
> + * @key_type: The key type to switch between access masks of different types.
> *
> * Returns: An access mask where each access right bit is set which is handled
> * in any of the active layers in @domain.
> */
> -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 init_layer_masks(const struct landlock_ruleset *const domain,
> + const access_mask_t access_request,
> + layer_mask_t (*const layer_masks)[],
> + const enum landlock_key_type key_type)
> {
> access_mask_t handled_accesses = 0;
> - size_t layer_level;
> + size_t layer_level, num_access;
> + get_access_mask_t *get_access_mask;
> +
> + switch (key_type) {
> + case LANDLOCK_KEY_INODE:
> + get_access_mask = landlock_get_fs_access_mask;
> + num_access = LANDLOCK_NUM_ACCESS_FS;
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + return 0;
> + }
> +
> + memset(layer_masks, 0,
> + array_size(sizeof((*layer_masks)[0]), num_access));
>
> - memset(layer_masks, 0, sizeof(*layer_masks));
> /* An empty access request can happen because of O_WRONLY | O_RDWR. */
> if (!access_request)
> return 0;
> @@ -657,14 +676,13 @@ init_layer_masks(const struct landlock_ruleset *const domain,
> const unsigned long access_req = access_request;
> unsigned long access_bit;
>
> - for_each_set_bit(access_bit, &access_req,
> - ARRAY_SIZE(*layer_masks)) {
> + for_each_set_bit(access_bit, &access_req, num_access) {
> /*
> * Artificially handles all initially denied by default
> * access rights.
> */
> if (BIT_ULL(access_bit) &
> - (landlock_get_fs_access_mask(domain, layer_level) |
> + (get_access_mask(domain, layer_level) |
> ACCESS_INITIALLY_DENIED)) {
> (*layer_masks)[access_bit] |=
> BIT_ULL(layer_level);
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index 50baff4fcbb4..d9eb79ea9a89 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -259,11 +259,12 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>
> 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]);
> + layer_mask_t (*const layer_masks)[],
> + const 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)[LANDLOCK_NUM_ACCESS_FS]);
> +access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
> + const access_mask_t access_request,
> + layer_mask_t (*const layer_masks)[],
> + const enum landlock_key_type key_type);
>
> #endif /* _SECURITY_LANDLOCK_RULESET_H */
> --
> 2.25.1
>
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