Message-ID: <8c272564-1033-f100-23b6-db6579085fd0@huawei.com>
Date:   Mon, 16 May 2022 20:43:37 +0300
From:   Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To:     Mickaël Salaün <mic@...ikod.net>
CC:     <willemdebruijn.kernel@...il.com>,
        <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
        <netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
        <anton.sirazetdinov@...wei.com>
Subject: Re: [PATCH v5 04/15] landlock: helper functions refactoring



5/16/2022 8:14 PM, Mickaël Salaün пишет:
> 
> 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@...wei.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.

  Ok. I will. Thanks
> 
>> 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?

   Cause these helpers are going to be used both for filesystem and 
network. I moved them into ruleset.c/h
> 
>> -{
>> -    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.

   Ok. Do you have some tool that helps you with editing code with clang 
format?
> 
>>           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.
> 
   I missed that. scripts/checkpatch.pl did not show any problem here.
   I will fix it. Thanks.
> 
>>   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. :/
> 
   Thats strange, cause in my editor I have normal aligment of arguments.
   Could please share clang-format-14 tab size and other format 	parameters?
> 
>>               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.

   I moved helpers in rulset.c/h to use them both for filesystem
and network.
> 
>> +
>>   #endif /* _SECURITY_LANDLOCK_RULESET_H */
>> -- 
>> 2.25.1
>>
> .

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