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    Subject[PATCH 5.15 584/667] landlock: Define access_mask_t to enforce a consistent access mask size
    Date
    From: Mickaël Salaün <mic@digikod.net>

    commit 5f2ff33e10843ef51275c8611bdb7b49537aba5d upstream.

    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.

    Reviewed-by: Paul Moore <paul@paul-moore.com>
    Link: https://lore.kernel.org/r/20220506161102.525323-2-mic@digikod.net
    Cc: stable@vger.kernel.org
    Signed-off-by: Mickaël Salaün <mic@digikod.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    security/landlock/fs.c | 19 +++++++++++--------
    security/landlock/fs.h | 2 +-
    security/landlock/limits.h | 2 ++
    security/landlock/ruleset.c | 6 ++++--
    security/landlock/ruleset.h | 16 ++++++++++++----
    5 files changed, 30 insertions(+), 15 deletions(-)

    --- a/security/landlock/fs.c
    +++ b/security/landlock/fs.c
    @@ -152,7 +152,8 @@ retry:
    * @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;
    @@ -184,7 +185,8 @@ int landlock_append_fs_rule(struct landl

    static inline u64 unmask_layers(const struct landlock_ruleset *const domain,
    const struct path *const path,
    - const u32 access_request, u64 layer_mask)
    + const access_mask_t access_request,
    + u64 layer_mask)
    {
    const struct landlock_rule *rule;
    const struct inode *inode;
    @@ -224,7 +226,8 @@ static inline u64 unmask_layers(const st
    }

    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;
    @@ -309,7 +312,7 @@ jump_up:
    }

    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();
    @@ -512,7 +515,7 @@ static int hook_sb_pivotroot(const struc

    /* 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:
    @@ -565,7 +568,7 @@ static int hook_path_link(struct 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;
    @@ -635,9 +638,9 @@ static int hook_path_rmdir(const struct

    /* 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. */
    --- a/security/landlock/fs.h
    +++ b/security/landlock/fs.h
    @@ -66,6 +66,6 @@ __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);
    + access_mask_t access_hierarchy);

    #endif /* _SECURITY_LANDLOCK_FS_H */
    --- 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>

    @@ -19,6 +20,7 @@

    #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)

    /* clang-format on */

    --- a/security/landlock/ruleset.c
    +++ b/security/landlock/ruleset.c
    @@ -45,7 +45,8 @@ static struct landlock_ruleset *create_r
    return new_ruleset;
    }

    -struct landlock_ruleset *landlock_create_ruleset(const u32 fs_access_mask)
    +struct landlock_ruleset *
    +landlock_create_ruleset(const access_mask_t fs_access_mask)
    {
    struct landlock_ruleset *new_ruleset;

    @@ -228,7 +229,8 @@ static void build_check_layer(void)

    /* @ruleset must be locked by the caller. */
    int landlock_insert_rule(struct landlock_ruleset *const ruleset,
    - struct landlock_object *const object, const u32 access)
    + struct landlock_object *const object,
    + const access_mask_t access)
    {
    struct landlock_layer layers[] = { {
    .access = access,
    --- 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);
    +
    /**
    * struct landlock_layer - Access rights for a given layer
    */
    @@ -28,7 +35,7 @@ struct landlock_layer {
    * @access: Bitfield of allowed actions on the kernel object. They are
    * relative to the object type (e.g. %LANDLOCK_ACTION_FS_READ).
    */
    - u16 access;
    + access_mask_t access;
    };

    /**
    @@ -135,19 +142,20 @@ struct landlock_ruleset {
    * layers are set once and never changed for the
    * lifetime of the ruleset.
    */
    - u16 fs_access_masks[];
    + access_mask_t fs_access_masks[];
    };
    };
    };

    -struct landlock_ruleset *landlock_create_ruleset(const u32 fs_access_mask);
    +struct landlock_ruleset *
    +landlock_create_ruleset(const access_mask_t fs_access_mask);

    void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
    void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);

    int landlock_insert_rule(struct landlock_ruleset *const ruleset,
    struct landlock_object *const object,
    - const u32 access);
    + const access_mask_t access);

    struct landlock_ruleset *
    landlock_merge_ruleset(struct landlock_ruleset *const parent,

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