[PATCH v8 04/12] landlock: Move unmask_layers() and init_layer_masks()
Mickaël Salaün
mic at digikod.net
Thu Nov 17 18:42:08 UTC 2022
On 21/10/2022 17:26, Konstantin Meskhidze wrote:
> This patch moves unmask_layers() and init_layer_masks() helpers
> to ruleset.c to share with landlock network implementation in
…to share them with the Landlock network implementation in
> following commits.
>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
> ---
>
> Changes since v7:
> * Refactors commit message.
>
> Changes since v6:
> * Moves get_handled_accesses() helper from ruleset.c back to fs.c,
> cause it's not used in coming network commits.
>
> Changes since v5:
> * Splits commit.
> * Moves init_layer_masks() and get_handled_accesses() helpers
> to ruleset.c and makes then non-static.
> * Formats code with clang-format-14.
>
> ---
> security/landlock/fs.c | 103 ------------------------------------
> security/landlock/ruleset.c | 102 +++++++++++++++++++++++++++++++++++
> security/landlock/ruleset.h | 20 +++++++
> 3 files changed, 122 insertions(+), 103 deletions(-)
>
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index 710cfa1306de..240e42a8f788 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -226,60 +226,6 @@ 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])
> -{
> - 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
> @@ -303,55 +249,6 @@ get_handled_accesses(const struct landlock_ruleset *const domain)
> return access_dom & LANDLOCK_MASK_ACCESS_FS;
> }
>
> -/**
> - * init_layer_masks - Initialize layer masks from an access request
> - *
> - * Populates @layer_masks such that for each access right in @access_request,
> - * the bits for all the layers are set where this access right is handled.
> - *
> - * @domain: The domain that defines the current restrictions.
> - * @access_request: The requested access rights to check.
> - * @layer_masks: The layer masks to populate.
> - *
> - * Returns: An access mask where each access right bit is set which is handled
> - * in any of the active layers in @domain.
> - */
> -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)) {
> - /*
> - * Artificially handles all initially denied by default
> - * access rights.
> - */
> - if (BIT_ULL(access_bit) &
> - (landlock_get_fs_access_mask(domain, layer_level) |
> - ACCESS_INITIALLY_DENIED)) {
> - (*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.
> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> index 961ffe0c709e..02ab14439c43 100644
> --- a/security/landlock/ruleset.c
> +++ b/security/landlock/ruleset.c
> @@ -572,3 +572,105 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
> }
> return NULL;
> }
> +
> +/*
> + * @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)[LANDLOCK_NUM_ACCESS_FS])
> +{
> + 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;
> +}
> +
> +/**
> + * init_layer_masks - Initialize layer masks from an access request
> + *
> + * Populates @layer_masks such that for each access right in @access_request,
> + * the bits for all the layers are set where this access right is handled.
> + *
> + * @domain: The domain that defines the current restrictions.
> + * @access_request: The requested access rights to check.
> + * @layer_masks: The layer masks to populate.
> + *
> + * 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 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)) {
> + /*
> + * Artificially handles all initially denied by default
> + * access rights.
> + */
> + if (BIT_ULL(access_bit) &
> + (landlock_get_fs_access_mask(domain, layer_level) |
> + ACCESS_INITIALLY_DENIED)) {
This is a future bug in the a next commit when
landlock_get_fs_access_mask() is changed to get the network access mask.
My patch will fix this part but you'll need to do a new copy of this
function.
> + (*layer_masks)[access_bit] |=
> + BIT_ULL(layer_level);
> + handled_accesses |= BIT_ULL(access_bit);
> + }
> + }
> + }
> + return handled_accesses;
> +}
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index 608ab356bc3e..50baff4fcbb4 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -34,6 +34,16 @@ typedef u16 layer_mask_t;
> /* Makes sure all layers can be checked. */
> static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
>
> +/*
> + * All access rights that are denied by default whether they are handled or not
> + * by a ruleset/layer. This must be ORed with all ruleset->fs_access_masks[]
> + * entries when we need to get the absolute handled access masks.
> + */
> +/* clang-format off */
> +#define ACCESS_INITIALLY_DENIED ( \
> + LANDLOCK_ACCESS_FS_REFER)
> +/* clang-format on */
This ACCESS_INITIALLY_DENIED definition must be moved, not copied. You
can rename ACCESS_INITIALLY_DENIED to ACCESS_FS_INITIALLY_DENIED and
move this hunk before the access_mask_t definition.
> +
> /**
> * struct landlock_layer - Access rights for a given layer
> */
> @@ -246,4 +256,14 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
> LANDLOCK_SHIFT_ACCESS_FS) &
> LANDLOCK_MASK_ACCESS_FS;
> }
> +
> +bool unmask_layers(const struct landlock_rule *const rule,
All public Landlock helpers must be prefixed with "landlock_"
> + 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)[LANDLOCK_NUM_ACCESS_FS]);
There is a warning generated by checkpatch.pl about this line:
WARNING: function definition argument 'layer_mask_t' should also have
an identifier name
I think this is a bug in checkpatch.pl
Any though Andy, Joe, Dwaipayan or Lukas?
> +
> #endif /* _SECURITY_LANDLOCK_RULESET_H */
> --
> 2.25.1
>
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