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| author |   Mickaël Salaün <mic@digikod.net> | 2022-05-06 18:10:52 +0200 |
|---|---|---|
| committer | Mickaël Salaün <mic@digikod.net> | 2022-05-23 13:27:56 +0200 |
| commit | 75c542d6c6cc48720376862d5496d51509160dfd (patch) | |
| tree | f7411e602afa044becdad12369614e004c439fd1 /security | |
| parent | landlock: Define access_mask_t to enforce a consistent access mask size (diff) | |
| download | linux-dev-75c542d6c6cc48720376862d5496d51509160dfd.tar.xz linux-dev-75c542d6c6cc48720376862d5496d51509160dfd.zip | |
landlock: Reduce the maximum number of layers to 16
The maximum number of nested Landlock domains is currently 64. Because
of the following fix and to help reduce the stack size, let's reduce it
to 16. This seems large enough for a lot of use cases (e.g. sandboxed
init service, spawning a sandboxed SSH service, in nested sandboxed
containers). Reducing the number of nested domains may also help to
discover misuse of Landlock (e.g. creating a domain per rule).
Add and use a dedicated layer_mask_t typedef to fit with the number of
layers. This might be useful when changing it and to keep it consistent
with the maximum number of layers.
Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220506161102.525323-3-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Diffstat (limited to 'security')
| -rw-r--r-- | security/landlock/fs.c | 17 | ||||
| -rw-r--r-- | security/landlock/limits.h | 2 | ||||
| -rw-r--r-- | security/landlock/ruleset.h | 4 |
3 files changed, 12 insertions, 11 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index d4006add8bdf..f48c0a3b1e75 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -183,10 +183,10 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, /* Access-control management */ -static inline u64 unmask_layers(const struct landlock_ruleset *const domain, - const struct path *const path, - const access_mask_t access_request, - u64 layer_mask) +static inline layer_mask_t +unmask_layers(const struct landlock_ruleset *const domain, + const struct path *const path, const access_mask_t access_request, + layer_mask_t layer_mask) { const struct landlock_rule *rule; const struct inode *inode; @@ -212,11 +212,11 @@ static inline u64 unmask_layers(const struct landlock_ruleset *const domain, */ for (i = 0; i < rule->num_layers; i++) { const struct landlock_layer *const layer = &rule->layers[i]; - const u64 layer_level = BIT_ULL(layer->level - 1); + const layer_mask_t layer_bit = BIT_ULL(layer->level - 1); /* Checks that the layer grants access to the full request. */ if ((layer->access & access_request) == access_request) { - layer_mask &= ~layer_level; + layer_mask &= ~layer_bit; if (layer_mask == 0) return layer_mask; @@ -231,12 +231,9 @@ static int check_access_path(const struct landlock_ruleset *const domain, { bool allowed = false; struct path walker_path; - u64 layer_mask; + layer_mask_t layer_mask; size_t i; - /* Make sure all layers can be checked. */ - BUILD_BUG_ON(BITS_PER_TYPE(layer_mask) < LANDLOCK_MAX_NUM_LAYERS); - if (!access_request) return 0; if (WARN_ON_ONCE(!domain || !path)) diff --git a/security/landlock/limits.h b/security/landlock/limits.h index 41372f22837f..17c2a2e7fe1e 100644 --- a/security/landlock/limits.h +++ b/security/landlock/limits.h @@ -15,7 +15,7 @@ /* clang-format off */ -#define LANDLOCK_MAX_NUM_LAYERS 64 +#define LANDLOCK_MAX_NUM_LAYERS 16 #define LANDLOCK_MAX_NUM_RULES U32_MAX #define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_MAKE_SYM diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 8d5717594931..521af2848951 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -23,6 +23,10 @@ typedef u16 access_mask_t; /* Makes sure all filesystem access rights can be stored. */ static_assert(BITS_PER_TYPE(access_mask_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); + /** * struct landlock_layer - Access rights for a given layer */ |