Unverified Commit 5f2ff33e authored by Mickaël Salaün's avatar Mickaël Salaün
Browse files

landlock: Define access_mask_t to enforce a consistent access mask size 



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: default avatarPaul 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: default avatarMickaël Salaün <mic@digikod.net>
parent 6533d0c3

security/landlock/fs.c

+11 −8
Original line number Diff line number Diff line
@@ -152,7 +152,8 @@ 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;
@@ -184,7 +185,8 @@ 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 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 struct landlock_ruleset *const domain, 
}



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 @@ 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();
@@ -512,7 +515,7 @@ 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:
@@ -565,7 +568,7 @@ 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;
@@ -635,9 +638,9 @@ 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. */

security/landlock/fs.h

+1 −1
Original line number Diff line number Diff line
@@ -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 */

security/landlock/limits.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

security/landlock/ruleset.c

+4 −2
Original line number Diff line number Diff line
@@ -45,7 +45,8 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers) 
	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,

security/landlock/ruleset.h

+12 −4
Original line number Diff line number Diff line
@@ -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,