On Mon, Feb 21, 2022 at 4:15 PM Mickaël Salaün <mic@xxxxxxxxxxx> wrote: > > From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> > > 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@xxxxxxxxxxxxxxxxxxx> > Link: https://lore.kernel.org/r/20220221212522.320243-2-mic@xxxxxxxxxxx > --- > 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. > 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
