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bpf: Implement task local storage 

Similar to bpf_local_storage for sockets and inodes add local storage
for task_struct.

The life-cycle of storage is managed with the life-cycle of the
task_struct.  i.e. the storage is destroyed along with the owning task
with a callback to the bpf_task_storage_free from the task_free LSM
hook.

The BPF LSM allocates an __rcu pointer to the bpf_local_storage in
the security blob which are now stackable and can co-exist with other
LSMs.

The userspace map operations can be done by using a pid fd as a key
passed to the lookup, update and delete operations.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201106103747.2780972-3-kpsingh@chromium.org
This commit is contained in:
KP Singh 2020-11-06 10:37:40 +00:00 committed by Alexei Starovoitov
parent 9e7a4d9831
commit 4cf1bc1f10
10 changed files with 436 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
include/linux/bpf_lsm.h
View File

@ -7,6 +7,7 @@
#ifndef _LINUX_BPF_LSM_H
#define _LINUX_BPF_LSM_H
#include <linux/sched.h>
#include <linux/bpf.h>
#include <linux/lsm_hooks.h>
@ -35,9 +36,21 @@ static inline struct bpf_storage_blob *bpf_inode(
return inode->i_security + bpf_lsm_blob_sizes.lbs_inode;
}
static inline struct bpf_storage_blob *bpf_task(
const struct task_struct *task)
{
if (unlikely(!task->security))
return NULL;
return task->security + bpf_lsm_blob_sizes.lbs_task;
}
extern const struct bpf_func_proto bpf_inode_storage_get_proto;
extern const struct bpf_func_proto bpf_inode_storage_delete_proto;
extern const struct bpf_func_proto bpf_task_storage_get_proto;
extern const struct bpf_func_proto bpf_task_storage_delete_proto;
void bpf_inode_storage_free(struct inode *inode);
void bpf_task_storage_free(struct task_struct *task);
#else /* !CONFIG_BPF_LSM */
@ -53,10 +66,20 @@ static inline struct bpf_storage_blob *bpf_inode(
return NULL;
}
static inline struct bpf_storage_blob *bpf_task(
const struct task_struct *task)
{
return NULL;
}
static inline void bpf_inode_storage_free(struct inode *inode)
{
}
static inline void bpf_task_storage_free(struct task_struct *task)
{
}
#endif /* CONFIG_BPF_LSM */
#endif /* _LINUX_BPF_LSM_H */

1
include/linux/bpf_types.h
View File

@ -109,6 +109,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKHASH, sock_hash_ops)
#endif
#ifdef CONFIG_BPF_LSM
BPF_MAP_TYPE(BPF_MAP_TYPE_INODE_STORAGE, inode_storage_map_ops)
BPF_MAP_TYPE(BPF_MAP_TYPE_TASK_STORAGE, task_storage_map_ops)
#endif
BPF_MAP_TYPE(BPF_MAP_TYPE_CPUMAP, cpu_map_ops)
#if defined(CONFIG_XDP_SOCKETS)

39
include/uapi/linux/bpf.h
View File

@ -157,6 +157,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_STRUCT_OPS,
BPF_MAP_TYPE_RINGBUF,
BPF_MAP_TYPE_INODE_STORAGE,
BPF_MAP_TYPE_TASK_STORAGE,
};
/* Note that tracing related programs such as
@ -3742,6 +3743,42 @@ union bpf_attr {
* Return
* The helper returns **TC_ACT_REDIRECT** on success or
* **TC_ACT_SHOT** on error.
*
* void *bpf_task_storage_get(struct bpf_map *map, struct task_struct *task, void *value, u64 flags)
* Description
* Get a bpf_local_storage from the *task*.
*
* Logically, it could be thought of as getting the value from
* a *map* with *task* as the **key**. From this
* perspective, the usage is not much different from
* **bpf_map_lookup_elem**\ (*map*, **&**\ *task*) except this
* helper enforces the key must be an task_struct and the map must also
* be a **BPF_MAP_TYPE_TASK_STORAGE**.
*
* Underneath, the value is stored locally at *task* instead of
* the *map*. The *map* is used as the bpf-local-storage
* "type". The bpf-local-storage "type" (i.e. the *map*) is
* searched against all bpf_local_storage residing at *task*.
*
* An optional *flags* (**BPF_LOCAL_STORAGE_GET_F_CREATE**) can be
* used such that a new bpf_local_storage will be
* created if one does not exist. *value* can be used
* together with **BPF_LOCAL_STORAGE_GET_F_CREATE** to specify
* the initial value of a bpf_local_storage. If *value* is
* **NULL**, the new bpf_local_storage will be zero initialized.
* Return
* A bpf_local_storage pointer is returned on success.
*
* **NULL** if not found or there was an error in adding
* a new bpf_local_storage.
*
* long bpf_task_storage_delete(struct bpf_map *map, struct task_struct *task)
* Description
* Delete a bpf_local_storage from a *task*.
* Return
* 0 on success.
*
* **-ENOENT** if the bpf_local_storage cannot be found.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -3900,6 +3937,8 @@ union bpf_attr {
FN(bpf_per_cpu_ptr), \
FN(bpf_this_cpu_ptr), \
FN(redirect_peer), \
FN(task_storage_get), \
FN(task_storage_delete), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper

1
kernel/bpf/Makefile
View File

@ -6,6 +6,7 @@ obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_i
obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o
obj-${CONFIG_BPF_LSM} += bpf_task_storage.o
obj-$(CONFIG_BPF_SYSCALL) += disasm.o
obj-$(CONFIG_BPF_JIT) += trampoline.o
obj-$(CONFIG_BPF_SYSCALL) += btf.o

4
kernel/bpf/bpf_lsm.c
View File

@ -63,6 +63,10 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_spin_lock_proto;
case BPF_FUNC_spin_unlock:
return &bpf_spin_unlock_proto;
case BPF_FUNC_task_storage_get:
return &bpf_task_storage_get_proto;
case BPF_FUNC_task_storage_delete:
return &bpf_task_storage_delete_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}

315
kernel/bpf/bpf_task_storage.c Normal file
View File

@ -0,0 +1,315 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2020 Facebook
* Copyright 2020 Google LLC.
*/
#include <linux/pid.h>
#include <linux/sched.h>
#include <linux/rculist.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/bpf.h>
#include <linux/bpf_local_storage.h>
#include <linux/filter.h>
#include <uapi/linux/btf.h>
#include <linux/bpf_lsm.h>
#include <linux/btf_ids.h>
#include <linux/fdtable.h>
DEFINE_BPF_STORAGE_CACHE(task_cache);
static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
{
struct task_struct *task = owner;
struct bpf_storage_blob *bsb;
bsb = bpf_task(task);
if (!bsb)
return NULL;
return &bsb->storage;
}
static struct bpf_local_storage_data *
task_storage_lookup(struct task_struct *task, struct bpf_map *map,
bool cacheit_lockit)
{
struct bpf_local_storage *task_storage;
struct bpf_local_storage_map *smap;
struct bpf_storage_blob *bsb;
bsb = bpf_task(task);
if (!bsb)
return NULL;
task_storage = rcu_dereference(bsb->storage);
if (!task_storage)
return NULL;
smap = (struct bpf_local_storage_map *)map;
return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit);
}
void bpf_task_storage_free(struct task_struct *task)
{
struct bpf_local_storage_elem *selem;
struct bpf_local_storage *local_storage;
bool free_task_storage = false;
struct bpf_storage_blob *bsb;
struct hlist_node *n;
bsb = bpf_task(task);
if (!bsb)
return;
rcu_read_lock();
local_storage = rcu_dereference(bsb->storage);
if (!local_storage) {
rcu_read_unlock();
return;
}
/* Neither the bpf_prog nor the bpf-map's syscall
* could be modifying the local_storage->list now.
* Thus, no elem can be added-to or deleted-from the
* local_storage->list by the bpf_prog or by the bpf-map's syscall.
*
* It is racing with bpf_local_storage_map_free() alone
* when unlinking elem from the local_storage->list and
* the map's bucket->list.
*/
raw_spin_lock_bh(&local_storage->lock);
hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
/* Always unlink from map before unlinking from
* local_storage.
*/
bpf_selem_unlink_map(selem);
free_task_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, false);
}
raw_spin_unlock_bh(&local_storage->lock);
rcu_read_unlock();
/* free_task_storage should always be true as long as
* local_storage->list was non-empty.
*/
if (free_task_storage)
kfree_rcu(local_storage, rcu);
}
static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
{
struct bpf_local_storage_data *sdata;
struct task_struct *task;
unsigned int f_flags;
struct pid *pid;
int fd, err;
fd = *(int *)key;
pid = pidfd_get_pid(fd, &f_flags);
if (IS_ERR(pid))
return ERR_CAST(pid);
/* We should be in an RCU read side critical section, it should be safe
* to call pid_task.
*/
WARN_ON_ONCE(!rcu_read_lock_held());
task = pid_task(pid, PIDTYPE_PID);
if (!task) {
err = -ENOENT;
goto out;
}
sdata = task_storage_lookup(task, map, true);
put_pid(pid);
return sdata ? sdata->data : NULL;
out:
put_pid(pid);
return ERR_PTR(err);
}
static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags)
{
struct bpf_local_storage_data *sdata;
struct task_struct *task;
unsigned int f_flags;
struct pid *pid;
int fd, err;
fd = *(int *)key;
pid = pidfd_get_pid(fd, &f_flags);
if (IS_ERR(pid))
return PTR_ERR(pid);
/* We should be in an RCU read side critical section, it should be safe
* to call pid_task.
*/
WARN_ON_ONCE(!rcu_read_lock_held());
task = pid_task(pid, PIDTYPE_PID);
if (!task) {
err = -ENOENT;
goto out;
}
sdata = bpf_local_storage_update(
task, (struct bpf_local_storage_map *)map, value, map_flags);
err = PTR_ERR_OR_ZERO(sdata);
out:
put_pid(pid);
return err;
}
static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
{
struct bpf_local_storage_data *sdata;
sdata = task_storage_lookup(task, map, false);
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata));
return 0;
}
static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
{
struct task_struct *task;
unsigned int f_flags;
struct pid *pid;
int fd, err;
fd = *(int *)key;
pid = pidfd_get_pid(fd, &f_flags);
if (IS_ERR(pid))
return PTR_ERR(pid);
/* We should be in an RCU read side critical section, it should be safe
* to call pid_task.
*/
WARN_ON_ONCE(!rcu_read_lock_held());
task = pid_task(pid, PIDTYPE_PID);
if (!task) {
err = -ENOENT;
goto out;
}
err = task_storage_delete(task, map);
out:
put_pid(pid);
return err;
}
BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
task, void *, value, u64, flags)
{
struct bpf_local_storage_data *sdata;
if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
return (unsigned long)NULL;
/* explicitly check that the task_storage_ptr is not
* NULL as task_storage_lookup returns NULL in this case and
* bpf_local_storage_update expects the owner to have a
* valid storage pointer.
*/
if (!task_storage_ptr(task))
return (unsigned long)NULL;
sdata = task_storage_lookup(task, map, true);
if (sdata)
return (unsigned long)sdata->data;
/* This helper must only be called from places where the lifetime of the task
* is guaranteed. Either by being refcounted or by being protected
* by an RCU read-side critical section.
*/
if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
sdata = bpf_local_storage_update(
task, (struct bpf_local_storage_map *)map, value,
BPF_NOEXIST);
return IS_ERR(sdata) ? (unsigned long)NULL :
(unsigned long)sdata->data;
}
return (unsigned long)NULL;
}
BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
task)
{
/* This helper must only be called from places where the lifetime of the task
* is guaranteed. Either by being refcounted or by being protected
* by an RCU read-side critical section.
*/
return task_storage_delete(task, map);
}
static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
return -ENOTSUPP;
}
static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr)
{
struct bpf_local_storage_map *smap;
smap = bpf_local_storage_map_alloc(attr);
if (IS_ERR(smap))
return ERR_CAST(smap);
smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache);
return &smap->map;
}
static void task_storage_map_free(struct bpf_map *map)
{
struct bpf_local_storage_map *smap;
smap = (struct bpf_local_storage_map *)map;
bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
bpf_local_storage_map_free(smap);
}
static int task_storage_map_btf_id;
const struct bpf_map_ops task_storage_map_ops = {
.map_meta_equal = bpf_map_meta_equal,
.map_alloc_check = bpf_local_storage_map_alloc_check,
.map_alloc = task_storage_map_alloc,
.map_free = task_storage_map_free,
.map_get_next_key = notsupp_get_next_key,
.map_lookup_elem = bpf_pid_task_storage_lookup_elem,
.map_update_elem = bpf_pid_task_storage_update_elem,
.map_delete_elem = bpf_pid_task_storage_delete_elem,
.map_check_btf = bpf_local_storage_map_check_btf,
.map_btf_name = "bpf_local_storage_map",
.map_btf_id = &task_storage_map_btf_id,
.map_owner_storage_ptr = task_storage_ptr,
};
BTF_ID_LIST_SINGLE(bpf_task_storage_btf_ids, struct, task_struct)
const struct bpf_func_proto bpf_task_storage_get_proto = {
.func = bpf_task_storage_get,
.gpl_only = false,
.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_BTF_ID,
.arg2_btf_id = &bpf_task_storage_btf_ids[0],
.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
.arg4_type = ARG_ANYTHING,
};
const struct bpf_func_proto bpf_task_storage_delete_proto = {
.func = bpf_task_storage_delete,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_BTF_ID,
.arg2_btf_id = &bpf_task_storage_btf_ids[0],
};

3
kernel/bpf/syscall.c
View File

@ -773,7 +773,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
map->map_type != BPF_MAP_TYPE_ARRAY &&
map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
map->map_type != BPF_MAP_TYPE_SK_STORAGE &&
map->map_type != BPF_MAP_TYPE_INODE_STORAGE)
map->map_type != BPF_MAP_TYPE_INODE_STORAGE &&
map->map_type != BPF_MAP_TYPE_TASK_STORAGE)
return -ENOTSUPP;
if (map->spin_lock_off + sizeof(struct bpf_spin_lock) >
map->value_size) {

10
kernel/bpf/verifier.c
View File

@ -4469,6 +4469,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
func_id != BPF_FUNC_inode_storage_delete)
goto error;
break;
case BPF_MAP_TYPE_TASK_STORAGE:
if (func_id != BPF_FUNC_task_storage_get &&
func_id != BPF_FUNC_task_storage_delete)
goto error;
break;
default:
break;
}
@ -4547,6 +4552,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
if (map->map_type != BPF_MAP_TYPE_INODE_STORAGE)
goto error;
break;
case BPF_FUNC_task_storage_get:
case BPF_FUNC_task_storage_delete:
if (map->map_type != BPF_MAP_TYPE_TASK_STORAGE)
goto error;
break;
default:
break;
}

2
security/bpf/hooks.c
View File

@ -12,6 +12,7 @@ static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
#include <linux/lsm_hook_defs.h>
#undef LSM_HOOK
LSM_HOOK_INIT(inode_free_security, bpf_inode_storage_free),
LSM_HOOK_INIT(task_free, bpf_task_storage_free),
};
static int __init bpf_lsm_init(void)
@ -23,6 +24,7 @@ static int __init bpf_lsm_init(void)
struct lsm_blob_sizes bpf_lsm_blob_sizes __lsm_ro_after_init = {
.lbs_inode = sizeof(struct bpf_storage_blob),
.lbs_task = sizeof(struct bpf_storage_blob),
};
DEFINE_LSM(bpf) = {

39
tools/include/uapi/linux/bpf.h
View File

@ -157,6 +157,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_STRUCT_OPS,
BPF_MAP_TYPE_RINGBUF,
BPF_MAP_TYPE_INODE_STORAGE,
BPF_MAP_TYPE_TASK_STORAGE,
};
/* Note that tracing related programs such as
@ -3742,6 +3743,42 @@ union bpf_attr {
* Return
* The helper returns **TC_ACT_REDIRECT** on success or
* **TC_ACT_SHOT** on error.
*
* void *bpf_task_storage_get(struct bpf_map *map, struct task_struct *task, void *value, u64 flags)
* Description
* Get a bpf_local_storage from the *task*.
*
* Logically, it could be thought of as getting the value from
* a *map* with *task* as the **key**. From this
* perspective, the usage is not much different from
* **bpf_map_lookup_elem**\ (*map*, **&**\ *task*) except this
* helper enforces the key must be an task_struct and the map must also
* be a **BPF_MAP_TYPE_TASK_STORAGE**.
*
* Underneath, the value is stored locally at *task* instead of
* the *map*. The *map* is used as the bpf-local-storage
* "type". The bpf-local-storage "type" (i.e. the *map*) is
* searched against all bpf_local_storage residing at *task*.
*
* An optional *flags* (**BPF_LOCAL_STORAGE_GET_F_CREATE**) can be
* used such that a new bpf_local_storage will be
* created if one does not exist. *value* can be used
* together with **BPF_LOCAL_STORAGE_GET_F_CREATE** to specify
* the initial value of a bpf_local_storage. If *value* is
* **NULL**, the new bpf_local_storage will be zero initialized.
* Return
* A bpf_local_storage pointer is returned on success.
*
* **NULL** if not found or there was an error in adding
* a new bpf_local_storage.
*
* long bpf_task_storage_delete(struct bpf_map *map, struct task_struct *task)
* Description
* Delete a bpf_local_storage from a *task*.
* Return
* 0 on success.
*
* **-ENOENT** if the bpf_local_storage cannot be found.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -3900,6 +3937,8 @@ union bpf_attr {
FN(bpf_per_cpu_ptr), \
FN(bpf_this_cpu_ptr), \
FN(redirect_peer), \
FN(task_storage_get), \
FN(task_storage_delete), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper