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bpf: Change uapi for bpf iterator map elements 

Commit a5cbe05a66 ("bpf: Implement bpf iterator for
map elements") added bpf iterator support for
map elements. The map element bpf iterator requires
info to identify a particular map. In the above
commit, the attr->link_create.target_fd is used
to carry map_fd and an enum bpf_iter_link_info
is added to uapi to specify the target_fd actually
representing a map_fd:
    enum bpf_iter_link_info {
	BPF_ITER_LINK_UNSPEC = 0,
	BPF_ITER_LINK_MAP_FD = 1,

	MAX_BPF_ITER_LINK_INFO,
    };

This is an extensible approach as we can grow
enumerator for pid, cgroup_id, etc. and we can
unionize target_fd for pid, cgroup_id, etc.
But in the future, there are chances that
more complex customization may happen, e.g.,
for tasks, it could be filtered based on
both cgroup_id and user_id.

This patch changed the uapi to have fields
	__aligned_u64	iter_info;
	__u32		iter_info_len;
for additional iter_info for link_create.
The iter_info is defined as
	union bpf_iter_link_info {
		struct {
			__u32   map_fd;
		} map;
	};

So future extension for additional customization
will be easier. The bpf_iter_link_info will be
passed to target callback to validate and generic
bpf_iter framework does not need to deal it any
more.

Note that map_fd = 0 will be considered invalid
and -EBADF will be returned to user space.

Fixes: a5cbe05a66 ("bpf: Implement bpf iterator for map elements")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
This commit is contained in:
Yonghong Song 2020-08-04 22:50:56 -07:00 committed by Alexei Starovoitov
parent 6bcaf41f96
commit 5e7b30205c
6 changed files with 102 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/bpf.h
View File

@ -1214,15 +1214,17 @@ struct bpf_iter_aux_info {
struct bpf_map *map;
};
typedef int (*bpf_iter_check_target_t)(struct bpf_prog *prog,
struct bpf_iter_aux_info *aux);
typedef int (*bpf_iter_attach_target_t)(struct bpf_prog *prog,
union bpf_iter_link_info *linfo,
struct bpf_iter_aux_info *aux);
typedef void (*bpf_iter_detach_target_t)(struct bpf_iter_aux_info *aux);
#define BPF_ITER_CTX_ARG_MAX 2
struct bpf_iter_reg {
const char *target;
bpf_iter_check_target_t check_target;
bpf_iter_attach_target_t attach_target;
bpf_iter_detach_target_t detach_target;
u32 ctx_arg_info_size;
enum bpf_iter_link_info req_linfo;
struct bpf_ctx_arg_aux ctx_arg_info[BPF_ITER_CTX_ARG_MAX];
const struct bpf_iter_seq_info *seq_info;
};

15
include/uapi/linux/bpf.h
View File

@ -81,6 +81,12 @@ struct bpf_cgroup_storage_key {
__u32 attach_type; /* program attach type */
};
union bpf_iter_link_info {
struct {
__u32 map_fd;
} map;
};
/* BPF syscall commands, see bpf(2) man-page for details. */
enum bpf_cmd {
BPF_MAP_CREATE,
@ -249,13 +255,6 @@ enum bpf_link_type {
MAX_BPF_LINK_TYPE,
};
enum bpf_iter_link_info {
BPF_ITER_LINK_UNSPEC = 0,
BPF_ITER_LINK_MAP_FD = 1,
MAX_BPF_ITER_LINK_INFO,
};
/* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
*
* NONE(default): No further bpf programs allowed in the subtree.
@ -623,6 +622,8 @@ union bpf_attr {
};
__u32 attach_type; /* attach type */
__u32 flags; /* extra flags */
__aligned_u64 iter_info; /* extra bpf_iter_link_info */
__u32 iter_info_len; /* iter_info length */
} link_create;
struct { /* struct used by BPF_LINK_UPDATE command */

58
kernel/bpf/bpf_iter.c
View File

@ -338,8 +338,8 @@ static void bpf_iter_link_release(struct bpf_link *link)
struct bpf_iter_link *iter_link =
container_of(link, struct bpf_iter_link, link);
if (iter_link->aux.map)
bpf_map_put_with_uref(iter_link->aux.map);
if (iter_link->tinfo->reg_info->detach_target)
iter_link->tinfo->reg_info->detach_target(&iter_link->aux);
}
static void bpf_iter_link_dealloc(struct bpf_link *link)
@ -390,15 +390,35 @@ bool bpf_link_is_iter(struct bpf_link *link)
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
union bpf_iter_link_info __user *ulinfo;
struct bpf_link_primer link_primer;
struct bpf_iter_target_info *tinfo;
struct bpf_iter_aux_info aux = {};
union bpf_iter_link_info linfo;
struct bpf_iter_link *link;
u32 prog_btf_id, target_fd;
u32 prog_btf_id, linfo_len;
bool existed = false;
struct bpf_map *map;
int err;
if (attr->link_create.target_fd || attr->link_create.flags)
return -EINVAL;
memset(&linfo, 0, sizeof(union bpf_iter_link_info));
ulinfo = u64_to_user_ptr(attr->link_create.iter_info);
linfo_len = attr->link_create.iter_info_len;
if (!ulinfo ^ !linfo_len)
return -EINVAL;
if (ulinfo) {
err = bpf_check_uarg_tail_zero(ulinfo, sizeof(linfo),
linfo_len);
if (err)
return err;
linfo_len = min_t(u32, linfo_len, sizeof(linfo));
if (copy_from_user(&linfo, ulinfo, linfo_len))
return -EFAULT;
}
prog_btf_id = prog->aux->attach_btf_id;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
@ -411,13 +431,6 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
if (!existed)
return -ENOENT;
/* Make sure user supplied flags are target expected. */
target_fd = attr->link_create.target_fd;
if (attr->link_create.flags != tinfo->reg_info->req_linfo)
return -EINVAL;
if (!attr->link_create.flags && target_fd)
return -EINVAL;
link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
if (!link)
return -ENOMEM;
@ -431,28 +444,15 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
return err;
}
if (tinfo->reg_info->req_linfo == BPF_ITER_LINK_MAP_FD) {
map = bpf_map_get_with_uref(target_fd);
if (IS_ERR(map)) {
err = PTR_ERR(map);
goto cleanup_link;
}
aux.map = map;
err = tinfo->reg_info->check_target(prog, &aux);
if (tinfo->reg_info->attach_target) {
err = tinfo->reg_info->attach_target(prog, &linfo, &link->aux);
if (err) {
bpf_map_put_with_uref(map);
goto cleanup_link;
bpf_link_cleanup(&link_primer);
return err;
}
link->aux.map = map;
}
return bpf_link_settle(&link_primer);
cleanup_link:
bpf_link_cleanup(&link_primer);
return err;
}
static void init_seq_meta(struct bpf_iter_priv_data *priv_data,

37
kernel/bpf/map_iter.c
View File

@ -98,12 +98,21 @@ static struct bpf_iter_reg bpf_map_reg_info = {
.seq_info = &bpf_map_seq_info,
};
static int bpf_iter_check_map(struct bpf_prog *prog,
struct bpf_iter_aux_info *aux)
static int bpf_iter_attach_map(struct bpf_prog *prog,
union bpf_iter_link_info *linfo,
struct bpf_iter_aux_info *aux)
{
u32 key_acc_size, value_acc_size, key_size, value_size;
struct bpf_map *map = aux->map;
struct bpf_map *map;
bool is_percpu = false;
int err = -EINVAL;
if (!linfo->map.map_fd)
return -EBADF;
map = bpf_map_get_with_uref(linfo->map.map_fd);
if (IS_ERR(map))
return PTR_ERR(map);
if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
@ -112,7 +121,7 @@ static int bpf_iter_check_map(struct bpf_prog *prog,
else if (map->map_type != BPF_MAP_TYPE_HASH &&
map->map_type != BPF_MAP_TYPE_LRU_HASH &&
map->map_type != BPF_MAP_TYPE_ARRAY)
return -EINVAL;
goto put_map;
key_acc_size = prog->aux->max_rdonly_access;
value_acc_size = prog->aux->max_rdwr_access;
@ -122,10 +131,22 @@ static int bpf_iter_check_map(struct bpf_prog *prog,
else
value_size = round_up(map->value_size, 8) * num_possible_cpus();
if (key_acc_size > key_size || value_acc_size > value_size)
return -EACCES;
if (key_acc_size > key_size || value_acc_size > value_size) {
err = -EACCES;
goto put_map;
}
aux->map = map;
return 0;
put_map:
bpf_map_put_with_uref(map);
return err;
}
static void bpf_iter_detach_map(struct bpf_iter_aux_info *aux)
{
bpf_map_put_with_uref(aux->map);
}
DEFINE_BPF_ITER_FUNC(bpf_map_elem, struct bpf_iter_meta *meta,
@ -133,8 +154,8 @@ DEFINE_BPF_ITER_FUNC(bpf_map_elem, struct bpf_iter_meta *meta,
static const struct bpf_iter_reg bpf_map_elem_reg_info = {
.target = "bpf_map_elem",
.check_target = bpf_iter_check_map,
.req_linfo = BPF_ITER_LINK_MAP_FD,
.attach_target = bpf_iter_attach_map,
.detach_target = bpf_iter_detach_map,
.ctx_arg_info_size = 2,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__bpf_map_elem, key),

2
kernel/bpf/syscall.c
View File

@ -3883,7 +3883,7 @@ static int tracing_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *
return -EINVAL;
}
#define BPF_LINK_CREATE_LAST_FIELD link_create.flags
#define BPF_LINK_CREATE_LAST_FIELD link_create.iter_info_len
static int link_create(union bpf_attr *attr)
{
enum bpf_prog_type ptype;

37
net/core/bpf_sk_storage.c
View File

@ -1384,18 +1384,39 @@ static int bpf_iter_init_sk_storage_map(void *priv_data,
return 0;
}
static int bpf_iter_check_map(struct bpf_prog *prog,
struct bpf_iter_aux_info *aux)
static int bpf_iter_attach_map(struct bpf_prog *prog,
union bpf_iter_link_info *linfo,
struct bpf_iter_aux_info *aux)
{
struct bpf_map *map = aux->map;
struct bpf_map *map;
int err = -EINVAL;
if (!linfo->map.map_fd)
return -EBADF;
map = bpf_map_get_with_uref(linfo->map.map_fd);
if (IS_ERR(map))
return PTR_ERR(map);
if (map->map_type != BPF_MAP_TYPE_SK_STORAGE)
return -EINVAL;
goto put_map;
if (prog->aux->max_rdonly_access > map->value_size)
return -EACCES;
if (prog->aux->max_rdonly_access > map->value_size) {
err = -EACCES;
goto put_map;
}
aux->map = map;
return 0;
put_map:
bpf_map_put_with_uref(map);
return err;
}
static void bpf_iter_detach_map(struct bpf_iter_aux_info *aux)
{
bpf_map_put_with_uref(aux->map);
}
static const struct seq_operations bpf_sk_storage_map_seq_ops = {
@ -1414,8 +1435,8 @@ static const struct bpf_iter_seq_info iter_seq_info = {
static struct bpf_iter_reg bpf_sk_storage_map_reg_info = {
.target = "bpf_sk_storage_map",
.check_target = bpf_iter_check_map,
.req_linfo = BPF_ITER_LINK_MAP_FD,
.attach_target = bpf_iter_attach_map,
.detach_target = bpf_iter_detach_map,
.ctx_arg_info_size = 2,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__bpf_sk_storage_map, sk),