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Message-ID: <700956d7-9831-da1d-c397-d1fb45aaf5d7@digikod.net>
Date: Mon, 28 Nov 2022 21:22:54 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: "Konstantin Meskhidze (A)" <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 01/12] landlock: Make ruleset's access masks more
generic
On 28/11/2022 03:53, Konstantin Meskhidze (A) wrote:
>
>
> 11/17/2022 9:41 PM, Mickaël Salaün пишет:
>>
>> On 21/10/2022 17:26, Konstantin Meskhidze wrote:
>>> To support network type rules, this modification renames ruleset's
>>> access masks and modifies it's type to access_masks_t. This patch
>>> adds filesystem helper functions to add and get filesystem mask.
>>>
>>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>>> ---
>>>
>>> Changes since v7:
>>> * Refactors commit message.
>>>
>>> Changes since v6:
>>> * Adds a new access_masks_t for struct ruleset.
>>> * Renames landlock_set_fs_access_mask() to landlock_add_fs_access_mask()
>>> because it OR values.
>>> * Makes landlock_add_fs_access_mask() more resilient incorrect values.
>>> * Refactors landlock_get_fs_access_mask().
>>>
>>> Changes since v6:
>>> * Adds a new access_masks_t for struct ruleset.
>>> * Renames landlock_set_fs_access_mask() to landlock_add_fs_access_mask()
>>> because it OR values.
>>> * Makes landlock_add_fs_access_mask() more resilient incorrect values.
>>> * Refactors landlock_get_fs_access_mask().
>>>
>>> Changes since v5:
>>> * Changes access_mask_t to u32.
>>> * Formats code with clang-format-14.
>>>
>>> Changes since v4:
>>> * Deletes struct landlock_access_mask.
>>>
>>> Changes since v3:
>>> * Splits commit.
>>> * Adds get_mask, set_mask helpers for filesystem.
>>> * Adds new struct landlock_access_mask.
>>>
>>> ---
>>> security/landlock/fs.c | 10 +++++-----
>>> security/landlock/limits.h | 1 +
>>> security/landlock/ruleset.c | 17 +++++++++--------
>>> security/landlock/ruleset.h | 35 +++++++++++++++++++++++++++++++----
>>> security/landlock/syscalls.c | 7 ++++---
>>> 5 files changed, 50 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>>> index adcea0fe7e68..0d57c6479d29 100644
>>> --- a/security/landlock/fs.c
>>> +++ b/security/landlock/fs.c
>>> @@ -178,9 +178,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>>> return -EINVAL;
>>>
>>> /* Transforms relative access rights to absolute ones. */
>>> - access_rights |=
>>> - LANDLOCK_MASK_ACCESS_FS &
>>> - ~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED);
>>> + access_rights |= LANDLOCK_MASK_ACCESS_FS &
>>> + ~(landlock_get_fs_access_mask(ruleset, 0) |
>>> + ACCESS_INITIALLY_DENIED);
>>> object = get_inode_object(d_backing_inode(path->dentry));
>>> if (IS_ERR(object))
>>> return PTR_ERR(object);
>>> @@ -294,7 +294,7 @@ get_handled_accesses(const struct landlock_ruleset *const domain)
>>> size_t layer_level;
>>>
>>> for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
>>> - access_dom |= domain->fs_access_masks[layer_level];
>>> + access_dom |= landlock_get_fs_access_mask(domain, layer_level);
>>> return access_dom & LANDLOCK_MASK_ACCESS_FS;
>>
>> You can remove `& LANDLOCK_MASK_ACCESS_FS` here because it is now part
>> of landlock_get_fs_access_mask().
>
> Ok. I got it. Thanks.
>>
>>
>>> }
>>>
>>> @@ -336,7 +336,7 @@ init_layer_masks(const struct landlock_ruleset *const domain,
>>> * access rights.
>>> */
>>> if (BIT_ULL(access_bit) &
>>> - (domain->fs_access_masks[layer_level] |
>>> + (landlock_get_fs_access_mask(domain, layer_level) |
>>> ACCESS_INITIALLY_DENIED)) {
>>> (*layer_masks)[access_bit] |=
>>> BIT_ULL(layer_level);
>>> diff --git a/security/landlock/limits.h b/security/landlock/limits.h
>>> index 82288f0e9e5e..bafb3b8dc677 100644
>>> --- a/security/landlock/limits.h
>>> +++ b/security/landlock/limits.h
>>> @@ -21,6 +21,7 @@
>>> #define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_TRUNCATE
>>> #define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
>>> #define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
>>> +#define LANDLOCK_SHIFT_ACCESS_FS 0
>>>
>>> /* clang-format on */
>>>
>>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>>> index 996484f98bfd..1f3188b4e313 100644
>>> --- a/security/landlock/ruleset.c
>>> +++ b/security/landlock/ruleset.c
>>> @@ -29,7 +29,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>>> struct landlock_ruleset *new_ruleset;
>>>
>>> new_ruleset =
>>> - kzalloc(struct_size(new_ruleset, fs_access_masks, num_layers),
>>> + kzalloc(struct_size(new_ruleset, access_masks, num_layers),
>>> GFP_KERNEL_ACCOUNT);
>>> if (!new_ruleset)
>>> return ERR_PTR(-ENOMEM);
>>> @@ -40,7 +40,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>>> /*
>>> * hierarchy = NULL
>>> * num_rules = 0
>>> - * fs_access_masks[] = 0
>>> + * access_masks[] = 0
>>> */
>>> return new_ruleset;
>>> }
>>> @@ -55,7 +55,7 @@ landlock_create_ruleset(const access_mask_t fs_access_mask)
>>> return ERR_PTR(-ENOMSG);
>>> new_ruleset = create_ruleset(1);
>>> if (!IS_ERR(new_ruleset))
>>> - new_ruleset->fs_access_masks[0] = fs_access_mask;
>>> + landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
>>> return new_ruleset;
>>> }
>>>
>>> @@ -117,11 +117,12 @@ static void build_check_ruleset(void)
>>> .num_rules = ~0,
>>> .num_layers = ~0,
>>> };
>>> - typeof(ruleset.fs_access_masks[0]) fs_access_mask = ~0;
>>> + typeof(ruleset.access_masks[0]) access_masks = ~0;
>>>
>>> BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
>>> BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
>>> - BUILD_BUG_ON(fs_access_mask < LANDLOCK_MASK_ACCESS_FS);
>>> + BUILD_BUG_ON(access_masks <
>>> + (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
>>> }
>>>
>>> /**
>>> @@ -281,7 +282,7 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>>> err = -EINVAL;
>>> goto out_unlock;
>>> }
>>> - dst->fs_access_masks[dst->num_layers - 1] = src->fs_access_masks[0];
>>> + dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
>>>
>>> /* Merges the @src tree. */
>>> rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, &src->root,
>>> @@ -340,8 +341,8 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
>>> goto out_unlock;
>>> }
>>> /* Copies the parent layer stack and leaves a space for the new layer. */
>>> - memcpy(child->fs_access_masks, parent->fs_access_masks,
>>> - flex_array_size(parent, fs_access_masks, parent->num_layers));
>>> + memcpy(child->access_masks, parent->access_masks,
>>> + flex_array_size(parent, access_masks, parent->num_layers));
>>>
>>> if (WARN_ON_ONCE(!parent->hierarchy)) {
>>> err = -EINVAL;
>>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>>> index d43231b783e4..f2ad932d396c 100644
>>> --- a/security/landlock/ruleset.h
>>> +++ b/security/landlock/ruleset.h
>>> @@ -25,6 +25,11 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
>>> /* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
>>> static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
>>>
>>> +/* Ruleset access masks. */
>>> +typedef u16 access_masks_t;
>>> +/* Makes sure all ruleset access rights can be stored. */
>>> +static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
>>> +
>>> typedef u16 layer_mask_t;
>>> /* Makes sure all layers can be checked. */
>>> static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
>>> @@ -110,7 +115,7 @@ struct landlock_ruleset {
>>> * section. This is only used by
>>> * landlock_put_ruleset_deferred() when @usage reaches zero.
>>> * The fields @lock, @usage, @num_rules, @num_layers and
>>> - * @fs_access_masks are then unused.
>>> + * @access_masks are then unused.
>>> */
>>> struct work_struct work_free;
>>> struct {
>>> @@ -137,7 +142,7 @@ struct landlock_ruleset {
>>> */
>>> u32 num_layers;
>>> /**
>>> - * @fs_access_masks: Contains the subset of filesystem
>>> + * @access_masks: Contains the subset of filesystem
>>> * actions that are restricted by a ruleset. A domain
>>> * saves all layers of merged rulesets in a stack
>>> * (FAM), starting from the first layer to the last
>>> @@ -148,13 +153,13 @@ struct landlock_ruleset {
>>> * layers are set once and never changed for the
>>> * lifetime of the ruleset.
>>> */
>>> - access_mask_t fs_access_masks[];
>>> + access_masks_t access_masks[];
>>> };
>>> };
>>> };
>>>
>>> struct landlock_ruleset *
>>> -landlock_create_ruleset(const access_mask_t fs_access_mask);
>>> +landlock_create_ruleset(const access_mask_t access_mask);
>>>
>>> void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
>>> void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
>>> @@ -177,4 +182,26 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
>>> refcount_inc(&ruleset->usage);
>>> }
>>>
>>> +static inline void
>>> +landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
>>> + const access_mask_t fs_access_mask,
>>> + const u16 layer_level)
>>> +{
>>> + access_mask_t fs_mask = fs_access_mask & LANDLOCK_MASK_ACCESS_FS;
>>> +
>>> + /* Should already be checked in sys_landlock_create_ruleset(). */
>>> + WARN_ON_ONCE(fs_access_mask != fs_mask);
>>> + // TODO: Add tests to check "|=" and not "="
>>
>> This todo should be done and removed. No more todos must remain.
>>
> I delete it in 10/12 Patch when add network seltests.
You can delete it in this patch then. I'm reviewing the tests.
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