Patchwork [bpf-next,v8,07/11] landlock: Handle filesystem access control

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Submitter Mickaël Salaün
Date Feb. 27, 2018, 12:41 a.m.
Message ID <20180227004121.3633-8-mic@digikod.net>
Download mbox | patch
Permalink /patch/10244021/
State New
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Mickaël Salaün - Feb. 27, 2018, 12:41 a.m.
This add three Landlock: FS_WALK, FS_PICK and FS_GET.

The FS_WALK hook is used to walk through a file path. A program tied to
this hook will be evaluated for each directory traversal except the last
one if it is the leaf of the path.

The FS_PICK hook is used to validate a set of actions requested on a
file. This actions are defined with triggers (e.g. read, write, open,
append...).

The FS_GET hook is used to tag open files, which is necessary to be able
to evaluate relative paths.  A program tied to this hook can tag a file
with an inode map.

A Landlock program can be chained to another if it is permitted by the
BPF verifier. A FS_WALK can be chained to a FS_PICK which can be chained
to a FS_GET.

The Landlock LSM hook registration is done after other LSM to only run
actions from user-space, via eBPF programs, if the access was granted by
major (privileged) LSMs.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: James Morris <james.l.morris@oracle.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
---

Changes since v7:
* major rewrite with clean Landlock hooks able to deal with file paths

Changes since v6:
* add 3 more sub-events: IOCTL, LOCK, FCNTL
  https://lkml.kernel.org/r/2fbc99a6-f190-f335-bd14-04bdeed35571@digikod.net
* use the new security_add_hooks()
* explain the -Werror=unused-function
* constify pointers
* cleanup headers

Changes since v5:
* split hooks.[ch] into hooks.[ch] and hooks_fs.[ch]
* add more documentation
* cosmetic fixes
* rebase (SCALAR_VALUE)

Changes since v4:
* add LSM hook abstraction called Landlock event
  * use the compiler type checking to verify hooks use by an event
  * handle all filesystem related LSM hooks (e.g. file_permission,
    mmap_file, sb_mount...)
* register BPF programs for Landlock just after LSM hooks registration
* move hooks registration after other LSMs
* add failsafes to check if a hook is not used by the kernel
* allow partial raw value access form the context (needed for programs
  generated by LLVM)

Changes since v3:
* split commit
* add hooks dealing with struct inode and struct path pointers:
  inode_permission and inode_getattr
* add abstraction over eBPF helper arguments thanks to wrapping structs
---
 include/linux/lsm_hooks.h           |    5 +
 security/landlock/Makefile          |    5 +-
 security/landlock/common.h          |    9 +
 security/landlock/enforce_seccomp.c |   10 +
 security/landlock/hooks.c           |  121 +++++
 security/landlock/hooks.h           |   35 ++
 security/landlock/hooks_cred.c      |   52 ++
 security/landlock/hooks_cred.h      |    1 +
 security/landlock/hooks_fs.c        | 1021 +++++++++++++++++++++++++++++++++++
 security/landlock/hooks_fs.h        |   60 ++
 security/landlock/init.c            |   56 ++
 security/landlock/task.c            |   34 ++
 security/landlock/task.h            |   29 +
 security/security.c                 |   12 +-
 14 files changed, 1447 insertions(+), 3 deletions(-)
 create mode 100644 security/landlock/hooks.c
 create mode 100644 security/landlock/hooks.h
 create mode 100644 security/landlock/hooks_cred.c
 create mode 100644 security/landlock/hooks_cred.h
 create mode 100644 security/landlock/hooks_fs.c
 create mode 100644 security/landlock/hooks_fs.h
 create mode 100644 security/landlock/task.c
 create mode 100644 security/landlock/task.h

Patch

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index d71cf183f0be..c40163385b68 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2032,5 +2032,10 @@  void __init loadpin_add_hooks(void);
 #else
 static inline void loadpin_add_hooks(void) { };
 #endif
+#ifdef CONFIG_SECURITY_LANDLOCK
+extern void __init landlock_add_hooks(void);
+#else
+static inline void __init landlock_add_hooks(void) { }
+#endif /* CONFIG_SECURITY_LANDLOCK */
 
 #endif /* ! __LINUX_LSM_HOOKS_H */
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index 0e1dd4612ecc..d0f532a93b4e 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -1,5 +1,6 @@ 
 obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
 
-landlock-y := init.o chain.o \
+landlock-y := init.o chain.o task.o \
 	tag.o tag_fs.o \
-	enforce.o enforce_seccomp.o
+	enforce.o enforce_seccomp.o \
+	hooks.o hooks_cred.o hooks_fs.o
diff --git a/security/landlock/common.h b/security/landlock/common.h
index 245e4ccafcf2..6d36b70068d5 100644
--- a/security/landlock/common.h
+++ b/security/landlock/common.h
@@ -82,4 +82,13 @@  static inline enum landlock_hook_type get_type(struct bpf_prog *prog)
 	return prog->aux->extra->subtype.landlock_hook.type;
 }
 
+__maybe_unused
+static bool current_has_prog_type(enum landlock_hook_type hook_type)
+{
+	struct landlock_prog_set *prog_set;
+
+	prog_set = current->seccomp.landlock_prog_set;
+	return (prog_set && prog_set->programs[get_index(hook_type)]);
+}
+
 #endif /* _SECURITY_LANDLOCK_COMMON_H */
diff --git a/security/landlock/enforce_seccomp.c b/security/landlock/enforce_seccomp.c
index 8da72e868422..7d06ad26e0f8 100644
--- a/security/landlock/enforce_seccomp.c
+++ b/security/landlock/enforce_seccomp.c
@@ -22,6 +22,7 @@ 
 #include <linux/uaccess.h> /* get_user() */
 
 #include "enforce.h"
+#include "task.h"
 
 /* headers in include/linux/landlock.h */
 
@@ -64,6 +65,13 @@  int landlock_seccomp_prepend_prog(unsigned int flags,
 	if (err)
 		return err;
 
+	/* allocate current->security here to not have to handle this in
+	 * hook_nameidata_free_security() */
+	if (!current->security) {
+		current->security = landlock_new_task_security(GFP_KERNEL);
+		if (!current->security)
+			return -ENOMEM;
+	}
 	prog = bpf_prog_get(bpf_fd);
 	if (IS_ERR(prog)) {
 		err = PTR_ERR(prog);
@@ -86,6 +94,8 @@  int landlock_seccomp_prepend_prog(unsigned int flags,
 	return 0;
 
 free_task:
+	landlock_free_task_security(current->security);
+	current->security = NULL;
 	return err;
 }
 
diff --git a/security/landlock/hooks.c b/security/landlock/hooks.c
new file mode 100644
index 000000000000..e9535937a7b9
--- /dev/null
+++ b/security/landlock/hooks.c
@@ -0,0 +1,121 @@ 
+/*
+ * Landlock LSM - hook helpers
+ *
+ * Copyright © 2016-2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <asm/current.h>
+#include <linux/bpf.h> /* enum bpf_prog_aux */
+#include <linux/errno.h>
+#include <linux/filter.h> /* BPF_PROG_RUN() */
+#include <linux/rculist.h> /* list_add_tail_rcu */
+#include <uapi/linux/landlock.h> /* struct landlock_context */
+
+#include "common.h" /* struct landlock_rule, get_index() */
+#include "hooks.h" /* landlock_hook_ctx */
+
+#include "hooks_fs.h"
+
+/* return a Landlock program context (e.g. hook_ctx->fs_walk.prog_ctx) */
+static void *update_ctx(enum landlock_hook_type hook_type,
+		struct landlock_hook_ctx *hook_ctx,
+		const struct landlock_chain *chain)
+{
+	switch (hook_type) {
+	case LANDLOCK_HOOK_FS_WALK:
+		return landlock_update_ctx_fs_walk(hook_ctx->fs_walk, chain);
+	case LANDLOCK_HOOK_FS_PICK:
+		return landlock_update_ctx_fs_pick(hook_ctx->fs_pick, chain);
+	case LANDLOCK_HOOK_FS_GET:
+		return landlock_update_ctx_fs_get(hook_ctx->fs_get, chain);
+	}
+	WARN_ON(1);
+	return NULL;
+}
+
+/* save the program context (e.g. hook_ctx->fs_get.prog_ctx.inode_tag) */
+static int save_ctx(enum landlock_hook_type hook_type,
+		struct landlock_hook_ctx *hook_ctx,
+		struct landlock_chain *chain)
+{
+	switch (hook_type) {
+	case LANDLOCK_HOOK_FS_WALK:
+		return landlock_save_ctx_fs_walk(hook_ctx->fs_walk, chain);
+	case LANDLOCK_HOOK_FS_PICK:
+		return landlock_save_ctx_fs_pick(hook_ctx->fs_pick, chain);
+	case LANDLOCK_HOOK_FS_GET:
+		/* no need to save the cookie */
+		return 0;
+	}
+	WARN_ON(1);
+	return 1;
+}
+
+/**
+ * landlock_access_deny - run Landlock programs tied to a hook
+ *
+ * @hook_idx: hook index in the programs array
+ * @ctx: non-NULL valid eBPF context
+ * @prog_set: Landlock program set pointer
+ * @triggers: a bitmask to check if a program should be run
+ *
+ * Return true if at least one program return deny.
+ */
+static bool landlock_access_deny(enum landlock_hook_type hook_type,
+		struct landlock_hook_ctx *hook_ctx,
+		struct landlock_prog_set *prog_set, u64 triggers)
+{
+	struct landlock_prog_list *prog_list, *prev_list = NULL;
+	u32 hook_idx = get_index(hook_type);
+
+	if (!prog_set)
+		return false;
+
+	for (prog_list = prog_set->programs[hook_idx];
+			prog_list; prog_list = prog_list->prev) {
+		u32 ret;
+		void *prog_ctx;
+
+		/* check if @prog expect at least one of this triggers */
+		if (triggers && !(triggers & prog_list->prog->aux->extra->
+					subtype.landlock_hook.triggers))
+			continue;
+		prog_ctx = update_ctx(hook_type, hook_ctx, prog_list->chain);
+		if (!prog_ctx || WARN_ON(IS_ERR(prog_ctx)))
+			return true;
+		rcu_read_lock();
+		ret = BPF_PROG_RUN(prog_list->prog, prog_ctx);
+		rcu_read_unlock();
+		if (save_ctx(hook_type, hook_ctx, prog_list->chain))
+			return true;
+		/* deny access if a program returns a value different than 0 */
+		if (ret)
+			return true;
+		if (prev_list && prog_list->prev && prog_list->prev->prog->
+				aux->extra->subtype.landlock_hook.type ==
+				prev_list->prog->aux->extra->
+				subtype.landlock_hook.type)
+			WARN_ON(prog_list->prev != prev_list);
+		prev_list = prog_list;
+	}
+	return false;
+}
+
+int landlock_decide(enum landlock_hook_type hook_type,
+		struct landlock_hook_ctx *hook_ctx, u64 triggers)
+{
+	bool deny = false;
+
+#ifdef CONFIG_SECCOMP_FILTER
+	deny = landlock_access_deny(hook_type, hook_ctx,
+			current->seccomp.landlock_prog_set, triggers);
+#endif /* CONFIG_SECCOMP_FILTER */
+
+	/* should we use -EPERM or -EACCES? */
+	return deny ? -EACCES : 0;
+}
diff --git a/security/landlock/hooks.h b/security/landlock/hooks.h
new file mode 100644
index 000000000000..30ffd8ffa738
--- /dev/null
+++ b/security/landlock/hooks.h
@@ -0,0 +1,35 @@ 
+/*
+ * Landlock LSM - hooks helpers
+ *
+ * Copyright © 2016-2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <asm/current.h>
+#include <linux/sched.h> /* struct task_struct */
+#include <linux/seccomp.h>
+
+#include "hooks_fs.h"
+
+struct landlock_hook_ctx {
+	union {
+		struct landlock_hook_ctx_fs_walk *fs_walk;
+		struct landlock_hook_ctx_fs_pick *fs_pick;
+		struct landlock_hook_ctx_fs_get *fs_get;
+	};
+};
+
+static inline bool landlocked(const struct task_struct *task)
+{
+#ifdef CONFIG_SECCOMP_FILTER
+	return !!(task->seccomp.landlock_prog_set);
+#else
+	return false;
+#endif /* CONFIG_SECCOMP_FILTER */
+}
+
+int landlock_decide(enum landlock_hook_type, struct landlock_hook_ctx *, u64);
diff --git a/security/landlock/hooks_cred.c b/security/landlock/hooks_cred.c
new file mode 100644
index 000000000000..1e30b3a3fe0e
--- /dev/null
+++ b/security/landlock/hooks_cred.c
@@ -0,0 +1,52 @@ 
+/*
+ * Landlock LSM - private headers
+ *
+ * Copyright © 2017-2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/cred.h>
+#include <linux/lsm_hooks.h>
+#include <linux/slab.h> /* alloc(), kfree() */
+
+#include "common.h" /* LANDLOCK_NAME */
+#include "task.h"
+
+static void hook_cred_free(struct cred *cred)
+{
+	struct landlock_task_security *tsec = cred->security;
+
+	if (!tsec)
+		return;
+	cred->security = NULL;
+	landlock_free_task_security(tsec);
+}
+
+/* TODO: make Landlock exclusive until the LSM stacking infrastructure */
+static int hook_cred_prepare(struct cred *new, const struct cred *old,
+		gfp_t gfp)
+{
+	struct landlock_task_security *tsec;
+
+	/* TODO: only allocate if the current task is landlocked */
+	tsec = landlock_new_task_security(gfp);
+	if (!tsec)
+		return -ENOMEM;
+	new->security = tsec;
+	return 0;
+}
+
+static struct security_hook_list landlock_hooks[] = {
+	LSM_HOOK_INIT(cred_prepare, hook_cred_prepare),
+	LSM_HOOK_INIT(cred_free, hook_cred_free),
+};
+
+__init void landlock_add_hooks_cred(void)
+{
+	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
+			LANDLOCK_NAME);
+}
diff --git a/security/landlock/hooks_cred.h b/security/landlock/hooks_cred.h
new file mode 100644
index 000000000000..18ec646a7eb0
--- /dev/null
+++ b/security/landlock/hooks_cred.h
@@ -0,0 +1 @@ 
+__init void landlock_add_hooks_cred(void);
diff --git a/security/landlock/hooks_fs.c b/security/landlock/hooks_fs.c
new file mode 100644
index 000000000000..8f91800feef4
--- /dev/null
+++ b/security/landlock/hooks_fs.c
@@ -0,0 +1,1021 @@ 
+/*
+ * Landlock LSM - filesystem hooks
+ *
+ * Copyright © 2016-2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bpf.h> /* enum bpf_access_type */
+#include <linux/kernel.h> /* ARRAY_SIZE */
+#include <linux/lsm_hooks.h>
+#include <linux/rcupdate.h> /* synchronize_rcu() */
+#include <linux/stat.h> /* S_ISDIR */
+#include <linux/stddef.h> /* offsetof */
+#include <linux/types.h> /* uintptr_t */
+#include <linux/workqueue.h> /* INIT_WORK() */
+
+/* permissions translation */
+#include <linux/fs.h> /* MAY_* */
+#include <linux/mman.h> /* PROT_* */
+#include <linux/namei.h>
+
+/* hook arguments */
+#include <linux/cred.h>
+#include <linux/dcache.h> /* struct dentry */
+#include <linux/fs.h> /* struct inode, struct iattr */
+#include <linux/mm_types.h> /* struct vm_area_struct */
+#include <linux/mount.h> /* struct vfsmount */
+#include <linux/path.h> /* struct path */
+#include <linux/sched.h> /* struct task_struct */
+#include <linux/time.h> /* struct timespec */
+
+#include "chain.h"
+#include "common.h"
+#include "hooks_fs.h"
+#include "hooks.h"
+#include "tag.h"
+#include "task.h"
+
+/* fs_pick */
+
+#include <asm/page.h> /* PAGE_SIZE */
+#include <asm/syscall.h>
+#include <linux/dcache.h> /* d_path, dentry_path_raw */
+#include <linux/err.h> /* *_ERR */
+#include <linux/gfp.h> /* __get_free_page, GFP_KERNEL */
+#include <linux/path.h> /* struct path */
+#include <linux/sched/task_stack.h> /* task_pt_regs dependency */
+
+bool landlock_is_valid_access_fs_pick(int off, enum bpf_access_type type,
+		enum bpf_reg_type *reg_type, int *max_size)
+{
+	switch (off) {
+	case offsetof(struct landlock_ctx_fs_pick, cookie):
+		if (type != BPF_READ && type != BPF_WRITE)
+			return false;
+		*reg_type = SCALAR_VALUE;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_pick, chain):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = PTR_TO_LL_CHAIN;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_pick, inode):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = PTR_TO_INODE;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_pick, inode_lookup):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = SCALAR_VALUE;
+		/* TODO: check the bit mask */
+		*max_size = sizeof(u8);
+		return true;
+	default:
+		return false;
+	}
+}
+
+bool landlock_is_valid_access_fs_walk(int off, enum bpf_access_type type,
+		enum bpf_reg_type *reg_type, int *max_size)
+{
+	switch (off) {
+	case offsetof(struct landlock_ctx_fs_walk, cookie):
+		if (type != BPF_READ && type != BPF_WRITE)
+			return false;
+		*reg_type = SCALAR_VALUE;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_walk, chain):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = PTR_TO_LL_CHAIN;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_walk, inode):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = PTR_TO_INODE;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_walk, inode_lookup):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = SCALAR_VALUE;
+		/* TODO: check the bit mask */
+		*max_size = sizeof(u8);
+		return true;
+	default:
+		return false;
+	}
+}
+
+bool landlock_is_valid_access_fs_get(int off, enum bpf_access_type type,
+		enum bpf_reg_type *reg_type, int *max_size)
+{
+	switch (off) {
+	case offsetof(struct landlock_ctx_fs_get, cookie):
+		/* fs_get is the last possible hook, hence not useful to allow
+		 * cookie modification */
+		if (type != BPF_READ)
+			return false;
+		*reg_type = SCALAR_VALUE;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_get, chain):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = PTR_TO_LL_CHAIN;
+		*max_size = sizeof(u64);
+		return true;
+	case offsetof(struct landlock_ctx_fs_get, tag_object):
+		if (type != BPF_READ)
+			return false;
+		*reg_type = PTR_TO_LL_TAG_OBJ;
+		*max_size = sizeof(u64);
+		return true;
+	default:
+		return false;
+	}
+}
+
+/* fs_walk */
+
+struct landlock_walk_state {
+	u64 cookie;
+};
+
+struct landlock_walk_list {
+	/* array of states */
+	struct work_struct work;
+	struct landlock_walk_state *state;
+	struct inode *last_inode;
+	struct task_struct *task;
+	struct landlock_walk_list *next;
+	enum namei_type lookup_type;
+};
+
+/* allocate an array of states nested in a new struct landlock_walk_list */
+/* never return NULL */
+/* TODO: use a dedicated kmem_cache_alloc() instead of k*alloc() */
+static struct landlock_walk_list *new_walk_list(struct task_struct *task)
+{
+	struct landlock_walk_list *walk_list;
+	struct landlock_walk_state *walk_state;
+	struct landlock_prog_set *prog_set =
+		task->seccomp.landlock_prog_set;
+
+	/* allocate an array of cookies: one for each fs_walk program */
+	if (WARN_ON(!prog_set))
+		return ERR_PTR(-EFAULT);
+	/* fill with zero */
+	walk_state = kcalloc(prog_set->chain_last->index + 1,
+			sizeof(*walk_state), GFP_ATOMIC);
+	if (!walk_state)
+		return ERR_PTR(-ENOMEM);
+	walk_list = kzalloc(sizeof(*walk_list), GFP_ATOMIC);
+	if (!walk_list) {
+		kfree(walk_state);
+		return ERR_PTR(-ENOMEM);
+	}
+	walk_list->state = walk_state;
+	walk_list->task = task;
+	return walk_list;
+}
+
+static void free_walk_list(struct landlock_walk_list *walker)
+{
+	while (walker) {
+		struct landlock_walk_list *freeme = walker;
+
+		walker = walker->next;
+		/* iput() might sleep */
+		iput(freeme->last_inode);
+		kfree(freeme->state);
+		kfree(freeme);
+	}
+}
+
+/* called from workqueue */
+static void free_walk_list_deferred(struct work_struct *work)
+{
+	struct landlock_walk_list *walk_list;
+
+	synchronize_rcu();
+	walk_list = container_of(work, struct landlock_walk_list, work);
+	free_walk_list(walk_list);
+}
+
+void landlock_free_walk_list(struct landlock_walk_list *freeme)
+{
+	if (!freeme)
+		return;
+	INIT_WORK(&freeme->work, free_walk_list_deferred);
+	schedule_work(&freeme->work);
+}
+
+/* return NULL if there is no fs_walk programs */
+static struct landlock_walk_list *get_current_walk_list(
+		const struct inode *inode)
+{
+	struct landlock_walk_list **walk_list;
+	struct nameidata_lookup *lookup;
+
+	lookup = current_nameidata_lookup(inode);
+	if (IS_ERR(lookup))
+		/* -ENOENT */
+		return ERR_CAST(lookup);
+	if (WARN_ON(!lookup))
+		return ERR_PTR(-EFAULT);
+	walk_list = (struct landlock_walk_list **)&lookup->security;
+	if (!*walk_list) {
+		struct landlock_walk_list *new_list;
+
+		/* allocate a landlock_walk_list to be able to move it without
+		 * new allocation in hook_nameidata_put_lookup() */
+		new_list = new_walk_list(current);
+		if (IS_ERR_OR_NULL(new_list))
+			/* no fs_walk prog */
+			return ERR_CAST(new_list);
+		*walk_list = new_list;
+	}
+	(*walk_list)->lookup_type = lookup->type;
+	return *walk_list;
+}
+
+static inline u8 translate_lookup(enum namei_type type)
+{
+	/* TODO: Use bitmask instead, and add an autonomous LOOKUP_ROOT
+	 * (doesn't show when encountering a LAST_DOTDOT)? */
+	BUILD_BUG_ON(LAST_ROOT != LANDLOCK_CTX_FS_WALK_INODE_LOOKUP_ROOT);
+	BUILD_BUG_ON(LAST_DOT != LANDLOCK_CTX_FS_WALK_INODE_LOOKUP_DOT);
+	BUILD_BUG_ON(LAST_DOTDOT != LANDLOCK_CTX_FS_WALK_INODE_LOOKUP_DOTDOT);
+	return type & 3;
+}
+
+/* for now, handle syscalls dealing with up to 2 concurrent path walks */
+#define LANDLOCK_MAX_CONCURRENT_WALK 2
+
+/* retrieve the walk state strictly associated to an inode (i.e. when the
+ * actual walk is done) */
+/* never return NULL */
+static struct landlock_walk_list *get_saved_walk_list(struct inode *inode)
+{
+	struct landlock_task_security *tsec;
+	struct landlock_walk_list **walker, *walk_match = NULL;
+	unsigned int walk_nb = 0;
+
+	tsec = current_security();
+	if (WARN_ON(!tsec) || WARN_ON(!inode))
+		return ERR_PTR(-EFAULT);
+	/* find the walk that match the inode */
+	walker = &tsec->walk_list;
+	while (*walker) {
+		walk_nb++;
+		if (walk_nb > LANDLOCK_MAX_CONCURRENT_WALK) {
+			free_walk_list(*walker);
+			*walker = NULL;
+			break;
+		}
+		if (!walk_match && (*walker)->last_inode == inode)
+			walk_match = *walker;
+		walker = &(*walker)->next;
+	}
+	if (!walk_match) {
+		/* create empty walk states */
+		walk_match = new_walk_list(current);
+		if (WARN_ON(!walk_match))
+			return ERR_PTR(-EFAULT);
+		ihold(inode);
+		walk_match->last_inode = inode;
+		walk_match->next = tsec->walk_list;
+		tsec->walk_list = walk_match;
+	}
+	return walk_match;
+}
+
+/* Move the walk state/list in current->security.  It will be freed by
+ * hook_cred_free(). */
+static void hook_nameidata_put_lookup(struct nameidata_lookup *lookup,
+		struct inode *inode)
+{
+	struct landlock_task_security *tsec;
+	struct landlock_walk_list *walk_list = lookup->security;
+
+	if (!landlocked(current))
+		return;
+	if (!walk_list)
+		return;
+	if (!inode)
+		goto free_list;
+	if (WARN_ON(walk_list->task != current))
+		goto free_list;
+	tsec = current_security();
+	if (WARN_ON(!tsec))
+		goto free_list;
+	inode = igrab(inode);
+	if (!inode)
+		goto free_list;
+	walk_list->lookup_type = lookup->type;
+	walk_list->last_inode = inode;
+	walk_list->next = tsec->walk_list;
+	tsec->walk_list = walk_list;
+	return;
+
+free_list:
+	landlock_free_walk_list(walk_list);
+}
+
+struct landlock_hook_ctx_fs_walk {
+	struct landlock_walk_state *state;
+	struct landlock_ctx_fs_walk prog_ctx;
+};
+
+/* set cookie and chain */
+struct landlock_ctx_fs_walk *landlock_update_ctx_fs_walk(
+		struct landlock_hook_ctx_fs_walk *hook_ctx,
+		const struct landlock_chain *chain)
+{
+	if (WARN_ON(!hook_ctx))
+		return NULL;
+	if (WARN_ON(!hook_ctx->state))
+		return NULL;
+	/* cookie initially contains zero */
+	hook_ctx->prog_ctx.cookie = hook_ctx->state[chain->index].cookie;
+	hook_ctx->prog_ctx.chain = (uintptr_t)chain;
+	return &hook_ctx->prog_ctx;
+}
+
+/* save cookie */
+int landlock_save_ctx_fs_walk(struct landlock_hook_ctx_fs_walk *hook_ctx,
+		struct landlock_chain *chain)
+{
+	if (WARN_ON(!hook_ctx))
+		return 1;
+	if (WARN_ON(!hook_ctx->state))
+		return 1;
+	hook_ctx->state[chain->index].cookie = hook_ctx->prog_ctx.cookie;
+	return 0;
+}
+
+static int decide_fs_walk(int may_mask, struct inode *inode)
+{
+	struct landlock_walk_list *walk_list;
+	struct landlock_hook_ctx_fs_walk fs_walk = {};
+	struct landlock_hook_ctx hook_ctx = {
+		.fs_walk = &fs_walk,
+	};
+	const enum landlock_hook_type hook_type = LANDLOCK_HOOK_FS_WALK;
+
+	if (!current_has_prog_type(hook_type))
+		/* no fs_walk */
+		return 0;
+	if (WARN_ON(!inode))
+		return -EFAULT;
+	walk_list = get_current_walk_list(inode);
+	if (IS_ERR_OR_NULL(walk_list))
+		/* error or no fs_walk */
+		return PTR_ERR(walk_list);
+
+	fs_walk.state = walk_list->state;
+	/* init common data: inode, is_dot, is_dotdot, is_root */
+	fs_walk.prog_ctx.inode = (uintptr_t)inode;
+	fs_walk.prog_ctx.inode_lookup =
+		translate_lookup(walk_list->lookup_type);
+	return landlock_decide(hook_type, &hook_ctx, 0);
+}
+
+/* fs_pick */
+
+struct landlock_hook_ctx_fs_pick {
+	__u64 triggers;
+	struct landlock_walk_state *state;
+	struct landlock_ctx_fs_pick prog_ctx;
+};
+
+/* set cookie and chain */
+struct landlock_ctx_fs_pick *landlock_update_ctx_fs_pick(
+		struct landlock_hook_ctx_fs_pick *hook_ctx,
+		const struct landlock_chain *chain)
+{
+	if (WARN_ON(!hook_ctx))
+		return NULL;
+	if (WARN_ON(!hook_ctx->state))
+		return NULL;
+	/* cookie initially contains zero */
+	hook_ctx->prog_ctx.cookie = hook_ctx->state[chain->index].cookie;
+	hook_ctx->prog_ctx.chain = (uintptr_t)chain;
+	return &hook_ctx->prog_ctx;
+}
+
+/* save cookie */
+int landlock_save_ctx_fs_pick(struct landlock_hook_ctx_fs_pick *hook_ctx,
+		struct landlock_chain *chain)
+{
+	if (WARN_ON(!hook_ctx))
+		return 1;
+	if (WARN_ON(!hook_ctx->state))
+		return 1;
+	hook_ctx->state[chain->index].cookie = hook_ctx->prog_ctx.cookie;
+	return 0;
+}
+
+static int decide_fs_pick(__u64 triggers, struct inode *inode)
+{
+	struct landlock_walk_list *walk_list;
+	struct landlock_hook_ctx_fs_pick fs_pick = {};
+	struct landlock_hook_ctx hook_ctx = {
+		.fs_pick = &fs_pick,
+	};
+	const enum landlock_hook_type hook_type = LANDLOCK_HOOK_FS_PICK;
+
+	if (WARN_ON(!triggers))
+		return 0;
+	if (!current_has_prog_type(hook_type))
+		/* no fs_pick */
+		return 0;
+	if (WARN_ON(!inode))
+		return -EFAULT;
+	/* first, try to get the current walk (e.g. open(2)) */
+	walk_list = get_current_walk_list(inode);
+	if (!walk_list || PTR_ERR(walk_list) == -ENOENT) {
+		/* otherwise, the path walk may have end (e.g. access(2)) */
+		walk_list = get_saved_walk_list(inode);
+		if (IS_ERR(walk_list))
+			return PTR_ERR(walk_list);
+		if (WARN_ON(!walk_list))
+			return -EFAULT;
+	}
+	if (IS_ERR(walk_list))
+		return PTR_ERR(walk_list);
+
+	fs_pick.state = walk_list->state;
+	fs_pick.triggers = triggers,
+	/* init common data: inode */
+	fs_pick.prog_ctx.inode = (uintptr_t)inode;
+	fs_pick.prog_ctx.inode_lookup =
+		translate_lookup(walk_list->lookup_type);
+	return landlock_decide(hook_type, &hook_ctx, fs_pick.triggers);
+}
+
+/* fs_get */
+
+struct landlock_hook_ctx_fs_get {
+	struct landlock_walk_state *state;
+	struct landlock_ctx_fs_get prog_ctx;
+};
+
+/* set cookie and chain */
+struct landlock_ctx_fs_get *landlock_update_ctx_fs_get(
+		struct landlock_hook_ctx_fs_get *hook_ctx,
+		const struct landlock_chain *chain)
+{
+	if (WARN_ON(!hook_ctx))
+		return NULL;
+	if (WARN_ON(!hook_ctx->state))
+		return NULL;
+	hook_ctx->prog_ctx.cookie = hook_ctx->state[chain->index].cookie;
+	hook_ctx->prog_ctx.chain = (uintptr_t)chain;
+	return &hook_ctx->prog_ctx;
+}
+
+static int decide_fs_get(struct inode *inode,
+		struct landlock_tag_ref **tag_ref)
+{
+	struct landlock_walk_list *walk_list;
+	struct landlock_hook_ctx_fs_get fs_get = {};
+	struct landlock_hook_ctx hook_ctx = {
+		.fs_get = &fs_get,
+	};
+	struct landlock_tag_object tag_obj = {
+		.lock = &inode->i_lock,
+		.root = (struct landlock_tag_root **)&inode->i_security,
+		.ref = tag_ref,
+	};
+	const enum landlock_hook_type hook_type = LANDLOCK_HOOK_FS_GET;
+
+	if (!current_has_prog_type(hook_type))
+		/* no fs_get */
+		return 0;
+	if (WARN_ON(!inode))
+		return -EFAULT;
+	walk_list = get_saved_walk_list(inode);
+	if (IS_ERR(walk_list))
+		return PTR_ERR(walk_list);
+	if (WARN_ON(!walk_list))
+		return -EFAULT;
+	fs_get.state = walk_list->state;
+	/* init common data: tag_obj */
+	fs_get.prog_ctx.tag_object = (uintptr_t)&tag_obj;
+	return landlock_decide(hook_type, &hook_ctx, 0);
+}
+
+/* helpers */
+
+static u64 fs_may_to_triggers(int may_mask, umode_t mode)
+{
+	u64 ret = 0;
+
+	if (may_mask & MAY_EXEC)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_EXECUTE;
+	if (may_mask & MAY_READ) {
+		if (S_ISDIR(mode))
+			ret |= LANDLOCK_TRIGGER_FS_PICK_READDIR;
+		else
+			ret |= LANDLOCK_TRIGGER_FS_PICK_READ;
+	}
+	if (may_mask & MAY_WRITE)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_WRITE;
+	if (may_mask & MAY_APPEND)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_APPEND;
+	/* do not (re-)run fs_pick in hook_file_open() */
+	if (may_mask & MAY_OPEN)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_OPEN;
+	if (may_mask & MAY_CHROOT)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_CHROOT;
+	else if (may_mask & MAY_CHDIR)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_CHDIR;
+	/* XXX: ignore MAY_ACCESS */
+	WARN_ON(!ret);
+	return ret;
+}
+
+static inline u64 mem_prot_to_triggers(unsigned long prot, bool private)
+{
+	u64 ret = LANDLOCK_TRIGGER_FS_PICK_MAP;
+
+	/* private mapping do not write to files */
+	if (!private && (prot & PROT_WRITE))
+		ret |= LANDLOCK_TRIGGER_FS_PICK_WRITE;
+	if (prot & PROT_READ)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_READ;
+	if (prot & PROT_EXEC)
+		ret |= LANDLOCK_TRIGGER_FS_PICK_EXECUTE;
+	WARN_ON(!ret);
+	return ret;
+}
+
+/* binder hooks */
+
+static int hook_binder_transfer_file(struct task_struct *from,
+		struct task_struct *to, struct file *file)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!file))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_TRANSFER,
+			file_inode(file));
+}
+
+/* sb hooks */
+
+static int hook_sb_statfs(struct dentry *dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_GETATTR,
+			dentry->d_inode);
+}
+
+/* TODO: handle mount source and remount */
+static int hook_sb_mount(const char *dev_name, const struct path *path,
+		const char *type, unsigned long flags, void *data)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!path))
+		return 0;
+	if (WARN_ON(!path->dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_MOUNTON,
+			path->dentry->d_inode);
+}
+
+/*
+ * The @old_path is similar to a destination mount point.
+ */
+static int hook_sb_pivotroot(const struct path *old_path,
+		const struct path *new_path)
+{
+	int err;
+	struct landlock_task_security *tsec;
+
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!old_path))
+		return 0;
+	if (WARN_ON(!old_path->dentry))
+		return 0;
+	err = decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_MOUNTON,
+			old_path->dentry->d_inode);
+	if (err)
+		return err;
+	err = decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_CHROOT,
+			new_path->dentry->d_inode);
+	if (err)
+		return err;
+
+	/* handle root directory tag */
+	tsec = current_security();
+	if (!tsec->root) {
+		struct landlock_tag_fs *new_tag_fs;
+
+		new_tag_fs = landlock_new_tag_fs(new_path->dentry->d_inode);
+		if (IS_ERR(new_tag_fs))
+			return PTR_ERR(new_tag_fs);
+		tsec->root = new_tag_fs;
+	} else {
+		landlock_reset_tag_fs(tsec->root, new_path->dentry->d_inode);
+	}
+	return decide_fs_get(tsec->root->inode, &tsec->root->ref);
+}
+
+/* inode hooks */
+
+/* a directory inode contains only one dentry */
+static int hook_inode_create(struct inode *dir, struct dentry *dentry,
+		umode_t mode)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_CREATE, dir);
+}
+
+static int hook_inode_link(struct dentry *old_dentry, struct inode *dir,
+		struct dentry *new_dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!old_dentry)) {
+		int ret = decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_LINK,
+				old_dentry->d_inode);
+		if (ret)
+			return ret;
+	}
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_LINKTO, dir);
+}
+
+static int hook_inode_unlink(struct inode *dir, struct dentry *dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_UNLINK,
+			dentry->d_inode);
+}
+
+static int hook_inode_symlink(struct inode *dir, struct dentry *dentry,
+		const char *old_name)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_CREATE, dir);
+}
+
+static int hook_inode_mkdir(struct inode *dir, struct dentry *dentry,
+		umode_t mode)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_CREATE, dir);
+}
+
+static int hook_inode_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_RMDIR, dentry->d_inode);
+}
+
+static int hook_inode_mknod(struct inode *dir, struct dentry *dentry,
+		umode_t mode, dev_t dev)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_CREATE, dir);
+}
+
+static int hook_inode_rename(struct inode *old_dir, struct dentry *old_dentry,
+		struct inode *new_dir, struct dentry *new_dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	/* TODO: add artificial walk session from old_dir to old_dentry */
+	if (!WARN_ON(!old_dentry)) {
+		int ret = decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_RENAME,
+				old_dentry->d_inode);
+		if (ret)
+			return ret;
+	}
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_RENAMETO, new_dir);
+}
+
+static int hook_inode_readlink(struct dentry *dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_READ, dentry->d_inode);
+}
+
+/* ignore the inode_follow_link hook (could set is_symlink in the fs_walk
+ * context) */
+
+static int hook_inode_permission(struct inode *inode, int mask)
+{
+	int err;
+	u64 triggers;
+	struct landlock_tag_fs **tag_fs;
+	struct landlock_task_security *tsec;
+
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!inode))
+		return 0;
+
+	triggers = fs_may_to_triggers(mask, inode->i_mode);
+	/* decide_fs_walk() is exclusive with decide_fs_pick(): in a path walk,
+	 * ignore execute-only access on directory for any fs_pick program. */
+	if (triggers == LANDLOCK_TRIGGER_FS_PICK_EXECUTE &&
+			S_ISDIR(inode->i_mode))
+		return decide_fs_walk(mask, inode);
+
+	err = decide_fs_pick(triggers, inode);
+	if (err)
+		return err;
+
+	/* handle current working directory and root directory tags */
+	tsec = current_security();
+	if (triggers & LANDLOCK_TRIGGER_FS_PICK_CHDIR)
+		tag_fs = &tsec->cwd;
+	else if (triggers & LANDLOCK_TRIGGER_FS_PICK_CHROOT)
+		tag_fs = &tsec->root;
+	else
+		return 0;
+	if (!*tag_fs) {
+		struct landlock_tag_fs *new_tag_fs;
+
+		new_tag_fs = landlock_new_tag_fs(inode);
+		if (IS_ERR(new_tag_fs))
+			return PTR_ERR(new_tag_fs);
+		*tag_fs = new_tag_fs;
+	} else {
+		landlock_reset_tag_fs(*tag_fs, inode);
+	}
+	return decide_fs_get((*tag_fs)->inode, &(*tag_fs)->ref);
+}
+
+static int hook_inode_setattr(struct dentry *dentry, struct iattr *attr)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_SETATTR,
+			dentry->d_inode);
+}
+
+static int hook_inode_getattr(const struct path *path)
+{
+	/* TODO: link parent inode and path */
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!path))
+		return 0;
+	if (WARN_ON(!path->dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_GETATTR,
+			path->dentry->d_inode);
+}
+
+static int hook_inode_setxattr(struct dentry *dentry, const char *name,
+		const void *value, size_t size, int flags)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_SETATTR,
+			dentry->d_inode);
+}
+
+static int hook_inode_getxattr(struct dentry *dentry, const char *name)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_GETATTR,
+			dentry->d_inode);
+}
+
+static int hook_inode_listxattr(struct dentry *dentry)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_GETATTR,
+			dentry->d_inode);
+}
+
+static int hook_inode_removexattr(struct dentry *dentry, const char *name)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!dentry))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_SETATTR,
+			dentry->d_inode);
+}
+
+static int hook_inode_getsecurity(struct inode *inode, const char *name,
+		void **buffer, bool alloc)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_GETATTR, inode);
+}
+
+static int hook_inode_setsecurity(struct inode *inode, const char *name,
+		const void *value, size_t size, int flag)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_SETATTR, inode);
+}
+
+static int hook_inode_listsecurity(struct inode *inode, char *buffer,
+		size_t buffer_size)
+{
+	if (!landlocked(current))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_GETATTR, inode);
+}
+
+/* file hooks */
+
+static int hook_file_ioctl(struct file *file, unsigned int cmd,
+		unsigned long arg)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!file))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_IOCTL,
+			file_inode(file));
+}
+
+static int hook_file_lock(struct file *file, unsigned int cmd)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!file))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_LOCK, file_inode(file));
+}
+
+static int hook_file_fcntl(struct file *file, unsigned int cmd,
+		unsigned long arg)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!file))
+		return 0;
+	return decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_FCNTL,
+			file_inode(file));
+}
+
+static int hook_mmap_file(struct file *file, unsigned long reqprot,
+		unsigned long prot, unsigned long flags)
+{
+	if (!landlocked(current))
+		return 0;
+	/* file can be null for anonymous mmap */
+	if (!file)
+		return 0;
+	return decide_fs_pick(mem_prot_to_triggers(prot, flags & MAP_PRIVATE),
+			file_inode(file));
+}
+
+static int hook_file_mprotect(struct vm_area_struct *vma,
+		unsigned long reqprot, unsigned long prot)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!vma))
+		return 0;
+	if (!vma->vm_file)
+		return 0;
+	return decide_fs_pick(mem_prot_to_triggers(prot,
+				!(vma->vm_flags & VM_SHARED)),
+			file_inode(vma->vm_file));
+}
+
+static int hook_file_receive(struct file *file)
+{
+	int err;
+
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!file))
+		return 0;
+	err = decide_fs_pick(LANDLOCK_TRIGGER_FS_PICK_RECEIVE,
+			file_inode(file));
+	if (err)
+		return err;
+
+	return decide_fs_get(file_inode(file),
+			(struct landlock_tag_ref **)&file->f_security);
+}
+
+static int hook_file_open(struct file *file, const struct cred *cred)
+{
+	if (!landlocked(current))
+		return 0;
+	if (WARN_ON(!file))
+		return 0;
+	/* do not re-run fs_pick/LANDLOCK_TRIGGER_FS_PICK_OPEN here for now */
+	return decide_fs_get(file_inode(file),
+			(struct landlock_tag_ref **)&file->f_security);
+}
+
+static void hook_inode_free_security(struct inode *inode)
+{
+	if (!landlocked(current))
+		return;
+	WARN_ON(inode->i_security);
+}
+
+static void hook_file_free_security(struct file *file)
+{
+	if (!landlocked(current))
+		return;
+	/* free inode tags */
+	if (!file_inode(file))
+		return;
+	landlock_free_tag_ref(file->f_security, (struct landlock_tag_root **)
+			&file_inode(file)->i_security,
+			&file_inode(file)->i_lock);
+}
+
+static struct security_hook_list landlock_hooks[] = {
+	LSM_HOOK_INIT(binder_transfer_file, hook_binder_transfer_file),
+
+	LSM_HOOK_INIT(sb_statfs, hook_sb_statfs),
+	LSM_HOOK_INIT(sb_mount, hook_sb_mount),
+	LSM_HOOK_INIT(sb_pivotroot, hook_sb_pivotroot),
+
+	LSM_HOOK_INIT(inode_create, hook_inode_create),
+	LSM_HOOK_INIT(inode_link, hook_inode_link),
+	LSM_HOOK_INIT(inode_unlink, hook_inode_unlink),
+	LSM_HOOK_INIT(inode_symlink, hook_inode_symlink),
+	LSM_HOOK_INIT(inode_mkdir, hook_inode_mkdir),
+	LSM_HOOK_INIT(inode_rmdir, hook_inode_rmdir),
+	LSM_HOOK_INIT(inode_mknod, hook_inode_mknod),
+	LSM_HOOK_INIT(inode_rename, hook_inode_rename),
+	LSM_HOOK_INIT(inode_readlink, hook_inode_readlink),
+	LSM_HOOK_INIT(inode_permission, hook_inode_permission),
+	LSM_HOOK_INIT(inode_setattr, hook_inode_setattr),
+	LSM_HOOK_INIT(inode_getattr, hook_inode_getattr),
+	LSM_HOOK_INIT(inode_setxattr, hook_inode_setxattr),
+	LSM_HOOK_INIT(inode_getxattr, hook_inode_getxattr),
+	LSM_HOOK_INIT(inode_listxattr, hook_inode_listxattr),
+	LSM_HOOK_INIT(inode_removexattr, hook_inode_removexattr),
+	LSM_HOOK_INIT(inode_getsecurity, hook_inode_getsecurity),
+	LSM_HOOK_INIT(inode_setsecurity, hook_inode_setsecurity),
+	LSM_HOOK_INIT(inode_listsecurity, hook_inode_listsecurity),
+	LSM_HOOK_INIT(nameidata_put_lookup, hook_nameidata_put_lookup),
+
+	/* do not handle file_permission for now */
+	LSM_HOOK_INIT(inode_free_security, hook_inode_free_security),
+	LSM_HOOK_INIT(file_free_security, hook_file_free_security),
+	LSM_HOOK_INIT(file_ioctl, hook_file_ioctl),
+	LSM_HOOK_INIT(file_lock, hook_file_lock),
+	LSM_HOOK_INIT(file_fcntl, hook_file_fcntl),
+	LSM_HOOK_INIT(mmap_file, hook_mmap_file),
+	LSM_HOOK_INIT(file_mprotect, hook_file_mprotect),
+	LSM_HOOK_INIT(file_receive, hook_file_receive),
+	LSM_HOOK_INIT(file_open, hook_file_open),
+};
+
+__init void landlock_add_hooks_fs(void)
+{
+	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
+			LANDLOCK_NAME);
+}
diff --git a/security/landlock/hooks_fs.h b/security/landlock/hooks_fs.h
new file mode 100644
index 000000000000..71cd2e7c47d4
--- /dev/null
+++ b/security/landlock/hooks_fs.h
@@ -0,0 +1,60 @@ 
+/*
+ * Landlock LSM - filesystem hooks
+ *
+ * Copyright © 2017-2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bpf.h> /* enum bpf_access_type */
+
+#include "common.h" /* struct landlock_chain */
+
+/* needed for struct landlock_task_security */
+struct landlock_walk_list;
+
+void landlock_free_walk_list(struct landlock_walk_list *freeme);
+
+__init void landlock_add_hooks_fs(void);
+
+/* fs_pick */
+
+struct landlock_hook_ctx_fs_pick;
+
+bool landlock_is_valid_access_fs_pick(int off, enum bpf_access_type type,
+		enum bpf_reg_type *reg_type, int *max_size);
+
+struct landlock_ctx_fs_pick *landlock_update_ctx_fs_pick(
+		struct landlock_hook_ctx_fs_pick *hook_ctx,
+		const struct landlock_chain *chain);
+
+int landlock_save_ctx_fs_pick(struct landlock_hook_ctx_fs_pick *hook_ctx,
+		struct landlock_chain *chain);
+
+/* fs_walk */
+
+struct landlock_hook_ctx_fs_walk;
+
+bool landlock_is_valid_access_fs_walk(int off, enum bpf_access_type type,
+		enum bpf_reg_type *reg_type, int *max_size);
+
+struct landlock_ctx_fs_walk *landlock_update_ctx_fs_walk(
+		struct landlock_hook_ctx_fs_walk *hook_ctx,
+		const struct landlock_chain *chain);
+
+int landlock_save_ctx_fs_walk(struct landlock_hook_ctx_fs_walk *hook_ctx,
+		struct landlock_chain *chain);
+
+/* fs_get */
+
+struct landlock_hook_ctx_fs_get;
+
+bool landlock_is_valid_access_fs_get(int off, enum bpf_access_type type,
+		enum bpf_reg_type *reg_type, int *max_size);
+
+struct landlock_ctx_fs_get *landlock_update_ctx_fs_get(
+		struct landlock_hook_ctx_fs_get *hook_ctx,
+		const struct landlock_chain *chain);
diff --git a/security/landlock/init.c b/security/landlock/init.c
index ef2ee0742c53..3486272d17b2 100644
--- a/security/landlock/init.c
+++ b/security/landlock/init.c
@@ -12,8 +12,11 @@ 
 #include <linux/bpf.h> /* enum bpf_access_type */
 #include <linux/capability.h> /* capable */
 #include <linux/filter.h> /* struct bpf_prog */
+#include <linux/lsm_hooks.h>
 
 #include "common.h" /* LANDLOCK_* */
+#include "hooks_fs.h"
+#include "hooks_cred.h"
 
 static bool bpf_landlock_is_valid_access(int off, int size,
 		enum bpf_access_type type, struct bpf_insn_access_aux *info,
@@ -32,6 +35,28 @@  static bool bpf_landlock_is_valid_access(int off, int size,
 	if (size <= 0 || size > sizeof(__u64))
 		return false;
 
+	/* set register type and max size */
+	switch (prog_subtype->landlock_hook.type) {
+	case LANDLOCK_HOOK_FS_PICK:
+		if (!landlock_is_valid_access_fs_pick(off, type, &reg_type,
+					&max_size))
+			return false;
+		break;
+	case LANDLOCK_HOOK_FS_WALK:
+		if (!landlock_is_valid_access_fs_walk(off, type, &reg_type,
+					&max_size))
+			return false;
+		break;
+	case LANDLOCK_HOOK_FS_GET:
+		if (!landlock_is_valid_access_fs_get(off, type, &reg_type,
+					&max_size))
+			return false;
+		break;
+	default:
+		WARN_ON(1);
+		return false;
+	}
+
 	/* check memory range access */
 	switch (reg_type) {
 	case NOT_INIT:
@@ -158,6 +183,30 @@  static const struct bpf_func_proto *bpf_landlock_func_proto(
 	default:
 		break;
 	}
+
+	switch (hook_type) {
+	case LANDLOCK_HOOK_FS_WALK:
+	case LANDLOCK_HOOK_FS_PICK:
+		switch (func_id) {
+		case BPF_FUNC_inode_map_lookup:
+			return &bpf_inode_map_lookup_proto;
+		case BPF_FUNC_inode_get_tag:
+			return &bpf_inode_get_tag_proto;
+		default:
+			break;
+		}
+		break;
+	case LANDLOCK_HOOK_FS_GET:
+		switch (func_id) {
+		case BPF_FUNC_inode_get_tag:
+			return &bpf_inode_get_tag_proto;
+		case BPF_FUNC_landlock_set_tag:
+			return &bpf_landlock_set_tag_proto;
+		default:
+			break;
+		}
+		break;
+	}
 	return NULL;
 }
 
@@ -178,3 +227,10 @@  const struct bpf_verifier_ops landlock_verifier_ops = {
 const struct bpf_prog_ops landlock_prog_ops = {
 	.put_extra = bpf_landlock_put_extra,
 };
+
+void __init landlock_add_hooks(void)
+{
+	pr_info(LANDLOCK_NAME ": Ready to sandbox with seccomp\n");
+	landlock_add_hooks_cred();
+	landlock_add_hooks_fs();
+}
diff --git a/security/landlock/task.c b/security/landlock/task.c
new file mode 100644
index 000000000000..8932570d3314
--- /dev/null
+++ b/security/landlock/task.c
@@ -0,0 +1,34 @@ 
+/*
+ * Landlock LSM - task helpers
+ *
+ * Copyright © 2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/slab.h>
+#include <linux/types.h> /* gfp_t */
+
+#include "hooks_fs.h" /* landlock_free_walk_list() */
+#include "tag_fs.h"
+#include "task.h"
+
+/* TODO: inherit tsec->root and tsec->cwd on fork/execve */
+
+void landlock_free_task_security(struct landlock_task_security *tsec)
+{
+	if (!tsec)
+		return;
+	landlock_free_walk_list(tsec->walk_list);
+	landlock_free_tag_fs(tsec->root);
+	landlock_free_tag_fs(tsec->cwd);
+	kfree(tsec);
+}
+
+struct landlock_task_security *landlock_new_task_security(gfp_t gfp)
+{
+	return kzalloc(sizeof(struct landlock_task_security), gfp);
+}
diff --git a/security/landlock/task.h b/security/landlock/task.h
new file mode 100644
index 000000000000..31e640a6a4cb
--- /dev/null
+++ b/security/landlock/task.h
@@ -0,0 +1,29 @@ 
+/*
+ * Landlock LSM - task headers
+ *
+ * Copyright © 2018 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018 ANSSI
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _SECURITY_LANDLOCK_TASK_H
+#define _SECURITY_LANDLOCK_TASK_H
+
+#include <linux/types.h> /* gfp_t */
+
+#include "hooks_fs.h"
+#include "tag_fs.h"
+
+/* exclusively used by the current task (i.e. no concurrent access) */
+struct landlock_task_security {
+	struct landlock_walk_list *walk_list;
+	struct landlock_tag_fs *root, *cwd;
+};
+
+struct landlock_task_security *landlock_new_task_security(gfp_t gfp);
+void landlock_free_task_security(struct landlock_task_security *tsec);
+
+#endif /* _SECURITY_LANDLOCK_TASK_H */
diff --git a/security/security.c b/security/security.c
index 17053c7a1a77..5000b64a5363 100644
--- a/security/security.c
+++ b/security/security.c
@@ -76,10 +76,20 @@  int __init security_init(void)
 	loadpin_add_hooks();
 
 	/*
-	 * Load all the remaining security modules.
+	 * Load all remaining privileged security modules.
 	 */
 	do_security_initcalls();
 
+	/*
+	 * Load potentially-unprivileged security modules at the end.
+	 *
+	 * For an unprivileged access-control, we don't want to give the
+	 * ability to any process to do some checks (e.g. through an eBPF
+	 * program) on kernel objects (e.g. files) if a privileged security
+	 * policy forbid their access.
+	 */
+	landlock_add_hooks();
+
 	return 0;
 }