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Message-ID: <3f9fc69d-1604-d879-d341-8a831beabeea@huawei.com>
Date: Mon, 28 Nov 2022 05:53:52 +0300
From: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
To: Mickaël Salaün <mic@...ikod.net>
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
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.
>
>> + ruleset->access_masks[layer_level] |=
>> + (fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
>> +}
>> +
>> +static inline access_mask_t
>> +landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>> + const u16 layer_level)
>> +{
>> + return (ruleset->access_masks[layer_level] >>
>> + LANDLOCK_SHIFT_ACCESS_FS) &
>> + LANDLOCK_MASK_ACCESS_FS;
>> +}
>> #endif /* _SECURITY_LANDLOCK_RULESET_H */
>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
>> index 245cc650a4dc..71aca7f990bc 100644
>> --- a/security/landlock/syscalls.c
>> +++ b/security/landlock/syscalls.c
>> @@ -346,10 +346,11 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
>> }
>> /*
>> * Checks that allowed_access matches the @ruleset constraints
>> - * (ruleset->fs_access_masks[0] is automatically upgraded to 64-bits).
>> + * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
>> */
>> - if ((path_beneath_attr.allowed_access | ruleset->fs_access_masks[0]) !=
>> - ruleset->fs_access_masks[0]) {
>> + if ((path_beneath_attr.allowed_access |
>> + landlock_get_fs_access_mask(ruleset, 0)) !=
>> + landlock_get_fs_access_mask(ruleset, 0)) {
>> err = -EINVAL;
>> goto out_put_ruleset;
>> }
>> --
>> 2.25.1
>>
>
> I'll send a patch to be applied after this one.
> .
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