| Message ID | 20241109110856.222842-2-mic@digikod.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Refactor Landlock access mask management | expand |
On Sat, Nov 09, 2024 at 12:08:54PM +0100, Mickaël Salaün wrote: > Replace get_raw_handled_fs_accesses() with a generic > landlock_merge_access_masks(), and replace get_fs_domain() with a > generic landlock_match_ruleset(). These helpers will also be useful for > other types of access. Of course I need to update the commit messages with the new names... > > Cc: Günther Noack <gnoack@google.com> > Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> > Signed-off-by: Mickaël Salaün <mic@digikod.net> > Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net
On Sat, Nov 09, 2024 at 12:08:54PM +0100, Mickaël Salaün wrote: > Replace get_raw_handled_fs_accesses() with a generic > landlock_merge_access_masks(), and replace get_fs_domain() with a > generic landlock_match_ruleset(). These helpers will also be useful for > other types of access. > > Cc: Günther Noack <gnoack@google.com> > Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> > Signed-off-by: Mickaël Salaün <mic@digikod.net> > Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net > --- > > Changes since v3: > * Rename landlock_merge_access_masks() to landlock_union_access_masks(), > suggested by Günther. > * Rename landlock_match_ruleset() to landlock_get_applicable_domain(), > suggested by Günther. > * Rename the "ruleset" arguments to "domain" for consistency with these > new helpers. > * Use typeof_member(), suggested by Günther. Also include kernel.h > (instead of the new container_of.h to ease backports). > > Changes since v2: > * Create a new type union access_masks_all instead of changing struct > acces_masks. > * Replace get_fs_domain() with an explicit call to > landlock_match_ruleset(). > > Changes since v1: > * Rename landlock_filter_access_masks() to landlock_match_ruleset(). > * Rename local variables from domain to ruleset to mach helpers' > semantic. We'll rename and move these helpers when we'll have a > dedicated domain struct type. > * Rename the all_fs mask to any_fs. > * Add documentation, as suggested by Günther. > --- > security/landlock/fs.c | 31 ++++----------- > security/landlock/ruleset.h | 73 ++++++++++++++++++++++++++++++++---- > security/landlock/syscalls.c | 2 +- > 3 files changed, 74 insertions(+), 32 deletions(-) > > diff --git a/security/landlock/fs.c b/security/landlock/fs.c > index 7d79fc8abe21..e31b97a9f175 100644 > --- a/security/landlock/fs.c > +++ b/security/landlock/fs.c > @@ -388,38 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry) > unlikely(IS_PRIVATE(d_backing_inode(dentry)))); > } > > -static access_mask_t > -get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain) > -{ > - access_mask_t access_dom = 0; > - size_t layer_level; > - > - for (layer_level = 0; layer_level < domain->num_layers; layer_level++) > - access_dom |= > - landlock_get_raw_fs_access_mask(domain, layer_level); > - return access_dom; > -} > - > static access_mask_t > get_handled_fs_accesses(const struct landlock_ruleset *const domain) > { > /* Handles all initially denied by default access rights. */ > - return get_raw_handled_fs_accesses(domain) | > + return landlock_union_access_masks(domain).fs | > LANDLOCK_ACCESS_FS_INITIALLY_DENIED; > } > > -static const struct landlock_ruleset * > -get_fs_domain(const struct landlock_ruleset *const domain) > -{ > - if (!domain || !get_raw_handled_fs_accesses(domain)) > - return NULL; > - > - return domain; > -} > +static const struct access_masks any_fs = { > + .fs = ~0, > +}; > > static const struct landlock_ruleset *get_current_fs_domain(void) > { > - return get_fs_domain(landlock_get_current_domain()); > + return landlock_get_applicable_domain(landlock_get_current_domain(), > + any_fs); > } > > /* > @@ -1517,7 +1501,8 @@ static int hook_file_open(struct file *const file) > access_mask_t open_access_request, full_access_request, allowed_access, > optional_access; > const struct landlock_ruleset *const dom = > - get_fs_domain(landlock_cred(file->f_cred)->domain); > + landlock_get_applicable_domain( > + landlock_cred(file->f_cred)->domain, any_fs); > > if (!dom) > return 0; > diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h > index 61bdbc550172..698fa3114cf4 100644 > --- a/security/landlock/ruleset.h > +++ b/security/landlock/ruleset.h > @@ -11,6 +11,7 @@ > > #include <linux/bitops.h> > #include <linux/build_bug.h> > +#include <linux/kernel.h> > #include <linux/mutex.h> > #include <linux/rbtree.h> > #include <linux/refcount.h> > @@ -47,6 +48,15 @@ struct access_masks { > access_mask_t scope : LANDLOCK_NUM_SCOPE; > }; > > +union access_masks_all { > + struct access_masks masks; > + u32 all; > +}; > + > +/* Makes sure all fields are covered. */ > +static_assert(sizeof(typeof_member(union access_masks_all, masks)) == > + sizeof(typeof_member(union access_masks_all, all))); > + > typedef u16 layer_mask_t; > /* Makes sure all layers can be checked. */ > static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS); > @@ -260,6 +270,60 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset) > refcount_inc(&ruleset->usage); > } > > +/** > + * landlock_union_access_masks - Return all access rights handled in the > + * domain > + * > + * @domain: Landlock ruleset (used as a domain) > + * > + * Returns: an access_masks result of the OR of all the domain's access masks. > + */ > +static inline struct access_masks > +landlock_union_access_masks(const struct landlock_ruleset *const domain) > +{ > + union access_masks_all matches = {}; > + size_t layer_level; > + > + for (layer_level = 0; layer_level < domain->num_layers; layer_level++) { > + union access_masks_all layer = { > + .masks = domain->access_masks[layer_level], > + }; > + > + matches.all |= layer.all; > + } > + > + return matches.masks; > +} > + > +/** > + * landlock_get_applicable_domain - Return @domain if it applies to (handles) > + * the access rights specified in @masks Very minor wording suggestion: For clarity, I would suggest "at least one of": Return @domain if it applies to (handles) at least one of the access rights specified in @masks Otherwise this can be interpreted as "...all of the access rights specified in @masks". > + * > + * @domain: Landlock ruleset (used as a domain) > + * @masks: access masks > + * > + * Returns: @domain if any access rights specified in @masks is handled, or > + * NULL otherwise. > + */ > +static inline const struct landlock_ruleset * > +landlock_get_applicable_domain(const struct landlock_ruleset *const domain, > + const struct access_masks masks) > +{ > + const union access_masks_all masks_all = { > + .masks = masks, > + }; > + union access_masks_all merge = {}; > + > + if (!domain) > + return NULL; > + > + merge.masks = landlock_union_access_masks(domain); > + if (merge.all & masks_all.all) > + return domain; > + > + return NULL; > +} > + > static inline void > landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset, > const access_mask_t fs_access_mask, > @@ -295,19 +359,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset, > ruleset->access_masks[layer_level].scope |= mask; > } > > -static inline access_mask_t > -landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset, > - const u16 layer_level) > -{ > - return ruleset->access_masks[layer_level].fs; > -} > - > static inline access_mask_t > landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset, > const u16 layer_level) > { > /* Handles all initially denied by default access rights. */ > - return landlock_get_raw_fs_access_mask(ruleset, layer_level) | > + return ruleset->access_masks[layer_level].fs | > LANDLOCK_ACCESS_FS_INITIALLY_DENIED; > } > > diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c > index f5a0e7182ec0..c097d356fa45 100644 > --- a/security/landlock/syscalls.c > +++ b/security/landlock/syscalls.c > @@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, > return -ENOMSG; > > /* Checks that allowed_access matches the @ruleset constraints. */ > - mask = landlock_get_raw_fs_access_mask(ruleset, 0); > + mask = ruleset->access_masks[0].fs; > if ((path_beneath_attr.allowed_access | mask) != mask) > return -EINVAL; > > -- > 2.47.0 > Reviewed-by: Günther Noack <gnoack@google.com> Looks good, thanks! Names are much clearer now, IMHO.
On Sat, Nov 09, 2024 at 12:14:49PM +0100, Mickaël Salaün wrote: > On Sat, Nov 09, 2024 at 12:08:54PM +0100, Mickaël Salaün wrote: > > Replace get_raw_handled_fs_accesses() with a generic > > landlock_merge_access_masks(), and replace get_fs_domain() with a > > generic landlock_match_ruleset(). These helpers will also be useful for > > other types of access. > > Of course I need to update the commit messages with the new names... Yes, those are still using the old function names. At this point my other two remaining remarks are so minor, I think we can skip another version of this patch set.
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 7d79fc8abe21..e31b97a9f175 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -388,38 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry) unlikely(IS_PRIVATE(d_backing_inode(dentry)))); } -static access_mask_t -get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain) -{ - access_mask_t access_dom = 0; - size_t layer_level; - - for (layer_level = 0; layer_level < domain->num_layers; layer_level++) - access_dom |= - landlock_get_raw_fs_access_mask(domain, layer_level); - return access_dom; -} - static access_mask_t get_handled_fs_accesses(const struct landlock_ruleset *const domain) { /* Handles all initially denied by default access rights. */ - return get_raw_handled_fs_accesses(domain) | + return landlock_union_access_masks(domain).fs | LANDLOCK_ACCESS_FS_INITIALLY_DENIED; } -static const struct landlock_ruleset * -get_fs_domain(const struct landlock_ruleset *const domain) -{ - if (!domain || !get_raw_handled_fs_accesses(domain)) - return NULL; - - return domain; -} +static const struct access_masks any_fs = { + .fs = ~0, +}; static const struct landlock_ruleset *get_current_fs_domain(void) { - return get_fs_domain(landlock_get_current_domain()); + return landlock_get_applicable_domain(landlock_get_current_domain(), + any_fs); } /* @@ -1517,7 +1501,8 @@ static int hook_file_open(struct file *const file) access_mask_t open_access_request, full_access_request, allowed_access, optional_access; const struct landlock_ruleset *const dom = - get_fs_domain(landlock_cred(file->f_cred)->domain); + landlock_get_applicable_domain( + landlock_cred(file->f_cred)->domain, any_fs); if (!dom) return 0; diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 61bdbc550172..698fa3114cf4 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -11,6 +11,7 @@ #include <linux/bitops.h> #include <linux/build_bug.h> +#include <linux/kernel.h> #include <linux/mutex.h> #include <linux/rbtree.h> #include <linux/refcount.h> @@ -47,6 +48,15 @@ struct access_masks { access_mask_t scope : LANDLOCK_NUM_SCOPE; }; +union access_masks_all { + struct access_masks masks; + u32 all; +}; + +/* Makes sure all fields are covered. */ +static_assert(sizeof(typeof_member(union access_masks_all, masks)) == + sizeof(typeof_member(union access_masks_all, all))); + typedef u16 layer_mask_t; /* Makes sure all layers can be checked. */ static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS); @@ -260,6 +270,60 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset) refcount_inc(&ruleset->usage); } +/** + * landlock_union_access_masks - Return all access rights handled in the + * domain + * + * @domain: Landlock ruleset (used as a domain) + * + * Returns: an access_masks result of the OR of all the domain's access masks. + */ +static inline struct access_masks +landlock_union_access_masks(const struct landlock_ruleset *const domain) +{ + union access_masks_all matches = {}; + size_t layer_level; + + for (layer_level = 0; layer_level < domain->num_layers; layer_level++) { + union access_masks_all layer = { + .masks = domain->access_masks[layer_level], + }; + + matches.all |= layer.all; + } + + return matches.masks; +} + +/** + * landlock_get_applicable_domain - Return @domain if it applies to (handles) + * the access rights specified in @masks + * + * @domain: Landlock ruleset (used as a domain) + * @masks: access masks + * + * Returns: @domain if any access rights specified in @masks is handled, or + * NULL otherwise. + */ +static inline const struct landlock_ruleset * +landlock_get_applicable_domain(const struct landlock_ruleset *const domain, + const struct access_masks masks) +{ + const union access_masks_all masks_all = { + .masks = masks, + }; + union access_masks_all merge = {}; + + if (!domain) + return NULL; + + merge.masks = landlock_union_access_masks(domain); + if (merge.all & masks_all.all) + return domain; + + return NULL; +} + static inline void landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset, const access_mask_t fs_access_mask, @@ -295,19 +359,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset, ruleset->access_masks[layer_level].scope |= mask; } -static inline access_mask_t -landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset, - const u16 layer_level) -{ - return ruleset->access_masks[layer_level].fs; -} - static inline access_mask_t landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset, const u16 layer_level) { /* Handles all initially denied by default access rights. */ - return landlock_get_raw_fs_access_mask(ruleset, layer_level) | + return ruleset->access_masks[layer_level].fs | LANDLOCK_ACCESS_FS_INITIALLY_DENIED; } diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index f5a0e7182ec0..c097d356fa45 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, return -ENOMSG; /* Checks that allowed_access matches the @ruleset constraints. */ - mask = landlock_get_raw_fs_access_mask(ruleset, 0); + mask = ruleset->access_masks[0].fs; if ((path_beneath_attr.allowed_access | mask) != mask) return -EINVAL;
Replace get_raw_handled_fs_accesses() with a generic landlock_merge_access_masks(), and replace get_fs_domain() with a generic landlock_match_ruleset(). These helpers will also be useful for other types of access. Cc: Günther Noack <gnoack@google.com> Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net --- Changes since v3: * Rename landlock_merge_access_masks() to landlock_union_access_masks(), suggested by Günther. * Rename landlock_match_ruleset() to landlock_get_applicable_domain(), suggested by Günther. * Rename the "ruleset" arguments to "domain" for consistency with these new helpers. * Use typeof_member(), suggested by Günther. Also include kernel.h (instead of the new container_of.h to ease backports). Changes since v2: * Create a new type union access_masks_all instead of changing struct acces_masks. * Replace get_fs_domain() with an explicit call to landlock_match_ruleset(). Changes since v1: * Rename landlock_filter_access_masks() to landlock_match_ruleset(). * Rename local variables from domain to ruleset to mach helpers' semantic. We'll rename and move these helpers when we'll have a dedicated domain struct type. * Rename the all_fs mask to any_fs. * Add documentation, as suggested by Günther. --- security/landlock/fs.c | 31 ++++----------- security/landlock/ruleset.h | 73 ++++++++++++++++++++++++++++++++---- security/landlock/syscalls.c | 2 +- 3 files changed, 74 insertions(+), 32 deletions(-)