Messages in this thread | | | Date | Thu, 17 Mar 2022 09:36:36 +0100 | From | Mickaël Salaün <> | Subject | Re: [PATCH v1 01/11] landlock: Define access_mask_t to enforce a consistent access mask size |
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On 17/03/2022 02:26, Paul Moore wrote: > On Mon, Feb 21, 2022 at 4:15 PM Mickaël Salaün <mic@digikod.net> wrote: >> >> From: Mickaël Salaün <mic@linux.microsoft.com> >> >> Create and use the access_mask_t typedef to enforce a consistent access >> mask size and uniformly use a 16-bits type. This will helps transition >> to a 32-bits value one day. >> >> Add a build check to make sure all (filesystem) access rights fit in. >> This will be extended with a following commit. >> >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> >> Link: https://lore.kernel.org/r/20220221212522.320243-2-mic@digikod.net >> --- >> security/landlock/fs.c | 19 ++++++++++--------- >> security/landlock/fs.h | 2 +- >> security/landlock/limits.h | 2 ++ >> security/landlock/ruleset.c | 6 ++++-- >> security/landlock/ruleset.h | 17 +++++++++++++---- >> 5 files changed, 30 insertions(+), 16 deletions(-) >> >> diff --git a/security/landlock/fs.c b/security/landlock/fs.c >> index 97b8e421f617..9de2a460a762 100644 >> --- a/security/landlock/fs.c >> +++ b/security/landlock/fs.c >> @@ -150,7 +150,7 @@ static struct landlock_object *get_inode_object(struct inode *const inode) >> * @path: Should have been checked by get_path_from_fd(). >> */ >> int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, >> - const struct path *const path, u32 access_rights) >> + const struct path *const path, access_mask_t access_rights) >> { >> int err; >> struct landlock_object *object; >> @@ -182,8 +182,8 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, >> >> static inline u64 unmask_layers( >> const struct landlock_ruleset *const domain, >> - const struct path *const path, const u32 access_request, >> - u64 layer_mask) >> + const struct path *const path, >> + const access_mask_t access_request, u64 layer_mask) >> { >> const struct landlock_rule *rule; >> const struct inode *inode; >> @@ -223,7 +223,8 @@ static inline u64 unmask_layers( >> } >> >> static int check_access_path(const struct landlock_ruleset *const domain, >> - const struct path *const path, u32 access_request) >> + const struct path *const path, >> + const access_mask_t access_request) >> { >> bool allowed = false; >> struct path walker_path; >> @@ -308,7 +309,7 @@ static int check_access_path(const struct landlock_ruleset *const domain, >> } >> >> static inline int current_check_access_path(const struct path *const path, >> - const u32 access_request) >> + const access_mask_t access_request) >> { >> const struct landlock_ruleset *const dom = >> landlock_get_current_domain(); >> @@ -511,7 +512,7 @@ static int hook_sb_pivotroot(const struct path *const old_path, >> >> /* Path hooks */ >> >> -static inline u32 get_mode_access(const umode_t mode) >> +static inline access_mask_t get_mode_access(const umode_t mode) >> { >> switch (mode & S_IFMT) { >> case S_IFLNK: >> @@ -563,7 +564,7 @@ static int hook_path_link(struct dentry *const old_dentry, >> get_mode_access(d_backing_inode(old_dentry)->i_mode)); >> } >> >> -static inline u32 maybe_remove(const struct dentry *const dentry) >> +static inline access_mask_t maybe_remove(const struct dentry *const dentry) >> { >> if (d_is_negative(dentry)) >> return 0; >> @@ -631,9 +632,9 @@ static int hook_path_rmdir(const struct path *const dir, >> >> /* File hooks */ >> >> -static inline u32 get_file_access(const struct file *const file) >> +static inline access_mask_t get_file_access(const struct file *const file) >> { >> - u32 access = 0; >> + access_mask_t access = 0; >> >> if (file->f_mode & FMODE_READ) { >> /* A directory can only be opened in read mode. */ >> diff --git a/security/landlock/fs.h b/security/landlock/fs.h >> index 187284b421c9..74be312aad96 100644 >> --- a/security/landlock/fs.h >> +++ b/security/landlock/fs.h >> @@ -65,6 +65,6 @@ static inline struct landlock_superblock_security *landlock_superblock( >> __init void landlock_add_fs_hooks(void); >> >> int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, >> - const struct path *const path, u32 access_hierarchy); >> + const struct path *const path, access_mask_t access_hierarchy); >> >> #endif /* _SECURITY_LANDLOCK_FS_H */ >> diff --git a/security/landlock/limits.h b/security/landlock/limits.h >> index 2a0a1095ee27..458d1de32ed5 100644 >> --- a/security/landlock/limits.h >> +++ b/security/landlock/limits.h >> @@ -9,6 +9,7 @@ >> #ifndef _SECURITY_LANDLOCK_LIMITS_H >> #define _SECURITY_LANDLOCK_LIMITS_H >> >> +#include <linux/bitops.h> >> #include <linux/limits.h> >> #include <uapi/linux/landlock.h> >> >> @@ -17,5 +18,6 @@ >> >> #define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_MAKE_SYM >> #define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1) >> +#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS) > > The line above, and the static_assert() in ruleset.h are clever. I'll > admit I didn't even know the hweightX() macros existed until looking > at this code :) > > However, the LANDLOCK_NUM_ACCESS_FS is never really going to be used > outside the static_assert() in ruleset.h is it? I wonder if it would > be better to skip the extra macro and rewrite the static_assert like > this: > > static_assert(BITS_PER_TYPE(access_mask_t) >= > __const_hweight64(LANDLOCK_MASK_ACCESS_FS)); > > If not, I might suggest changing LANDLOCK_NUM_ACCESS_FS to > LANDLOCK_BITS_ACCESS_FS or something similar.
I declared LANDLOCK_NUM_ACCESS_FS in this patch to be able to have the static_assert() here and ease the review, but LANDLOCK_NUM_ACCESS_FS is really used in patch 6/11 to define an array size: get_handled_acceses(), init_layer_masks(), is_superset(), check_access_path_dual()…
> > >> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h >> index 2d3ed7ec5a0a..7e7cac68e443 100644 >> --- a/security/landlock/ruleset.h >> +++ b/security/landlock/ruleset.h >> @@ -9,13 +9,20 @@ >> #ifndef _SECURITY_LANDLOCK_RULESET_H >> #define _SECURITY_LANDLOCK_RULESET_H >> >> +#include <linux/bitops.h> >> +#include <linux/build_bug.h> >> #include <linux/mutex.h> >> #include <linux/rbtree.h> >> #include <linux/refcount.h> >> #include <linux/workqueue.h> >> >> +#include "limits.h" >> #include "object.h" >> >> +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); > > -- > paul-moore.com
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