[RFC PATCH bpf-next 09/13] bpf: Alloc and free bpf_prog id in bpf namespace

From: Yafang Shao
Date: Sun Mar 26 2023 - 05:22:55 EST

Next message: Yafang Shao: "[RFC PATCH bpf-next 11/13] bpf: Allow iterating bpf objects with CAP_BPF in bpf namespace"
Previous message: Yafang Shao: "[RFC PATCH bpf-next 08/13] bpf: Alloc and free bpf_map id in bpf namespace"
In reply to: Yafang Shao: "Re: [RFC PATCH bpf-next 08/13] bpf: Alloc and free bpf_map id in bpf namespace"
Next in thread: Yafang Shao: "[RFC PATCH bpf-next 11/13] bpf: Allow iterating bpf objects with CAP_BPF in bpf namespace"
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Similar to bpf map, We only expose the bpf map id under current bpf
namespace to user. The prog->aux->id is still the id in the init bpf
namespace.
The id of used_maps is also the id in current bpf namespace.

The result as follows,

Run bpftool in current namespace,
$ bpftool map show
4: array name kprobe_b.rodata flags 0x80
key 4B value 37B max_entries 1 memlock 360B
btf_id 96 frozen
pids kprobe(8790)
5: array name kprobe_b.data flags 0x400
key 4B value 4B max_entries 1 memlock 8192B
btf_id 96
pids kprobe(8790)

$ bpftool prog show
7: kprobe name kretprobe_run tag 0de47cc241a2b1b3 gpl
loaded_at 2023-03-21T10:20:58+0800 uid 0
xlated 56B jited 39B memlock 4096B map_ids 4
btf_id 96
9: kprobe name kprobe_run tag bf163b23cd3b174d gpl
loaded_at 2023-03-21T10:20:58+0800 uid 0
xlated 48B jited 35B memlock 4096B map_ids 4
btf_id 96

At the same time, run bpftool in init bpf namespace.
$ bpftool map show
18: array name kprobe_b.rodata flags 0x80
key 4B value 37B max_entries 1 memlock 360B
btf_id 96 frozen
pids kprobe(8790)
19: array name kprobe_b.data flags 0x400
key 4B value 4B max_entries 1 memlock 8192B
btf_id 96
pids kprobe(8790)

$ bpftool prog show
29: kprobe name kretprobe_run tag 0de47cc241a2b1b3 gpl
loaded_at 2023-03-21T10:20:58+0800 uid 0
xlated 56B jited 39B memlock 4096B map_ids 18
btf_id 96
pids kprobe(8790)
31: kprobe name kprobe_run tag bf163b23cd3b174d gpl
loaded_at 2023-03-21T10:20:58+0800 uid 0
xlated 48B jited 35B memlock 4096B map_ids 18
btf_id 96
pids kprobe(8790)

In init bpf namespace, bpftool can also show other bpf progs, but the
bpftool running in the new bpf namespace can't.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
include/linux/bpf.h | 3 +-
kernel/bpf/bpf_namespace.c | 1 +
kernel/bpf/syscall.c | 56 ++++++++++---------------------
tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 3 +-
4 files changed, 22 insertions(+), 41 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2a1f19c..16f2a01 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1416,6 +1416,7 @@ struct bpf_prog_aux {
struct work_struct work;
struct rcu_head rcu;
};
+ struct bpf_obj_id *obj_id;
};

struct bpf_prog {
@@ -1940,8 +1941,6 @@ struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum bpf_prog_type type,
struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog);
void bpf_prog_put(struct bpf_prog *prog);

-void bpf_prog_free_id(struct bpf_prog *prog);
-
struct btf_field *btf_record_find(const struct btf_record *rec,
u32 offset, u32 field_mask);
void btf_record_free(struct btf_record *rec);
diff --git a/kernel/bpf/bpf_namespace.c b/kernel/bpf/bpf_namespace.c
index 6a6ef70..8c70945 100644
--- a/kernel/bpf/bpf_namespace.c
+++ b/kernel/bpf/bpf_namespace.c
@@ -12,6 +12,7 @@

#define MAX_BPF_NS_LEVEL 32
DEFINE_SPINLOCK(map_idr_lock);
+DEFINE_SPINLOCK(prog_idr_lock);
static struct kmem_cache *bpfns_cachep;
static struct kmem_cache *obj_id_cache[MAX_PID_NS_LEVEL];
static struct ns_common *bpfns_get(struct task_struct *task);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 1335200..4725924 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -48,8 +48,6 @@
#define BPF_OBJ_FLAG_MASK (BPF_F_RDONLY | BPF_F_WRONLY)

DEFINE_PER_CPU(int, bpf_prog_active);
-static DEFINE_IDR(prog_idr);
-DEFINE_SPINLOCK(prog_idr_lock);
static DEFINE_IDR(link_idr);
DEFINE_SPINLOCK(link_idr_lock);

@@ -1983,32 +1981,10 @@ static void bpf_audit_prog(const struct bpf_prog *prog, unsigned int op)
if (unlikely(!ab))
return;
audit_log_format(ab, "prog-id=%u op=%s",
- prog->aux->id, bpf_audit_str[op]);
+ bpf_obj_id_vnr(prog->aux->obj_id), bpf_audit_str[op]);
audit_log_end(ab);
}

-static int bpf_prog_alloc_id(struct bpf_prog *prog)
-{
- int id;
-
- idr_preload(GFP_KERNEL);
- spin_lock_bh(&prog_idr_lock);
- id = idr_alloc_cyclic(&prog_idr, prog, 1, INT_MAX, GFP_ATOMIC);
- spin_unlock_bh(&prog_idr_lock);
- idr_preload_end();
-
- return id;
-}
-
-void bpf_prog_free_id(struct bpf_prog *prog)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&prog_idr_lock, flags);
- idr_remove(&prog_idr, prog->aux->id);
- spin_unlock_irqrestore(&prog_idr_lock, flags);
-}
-
static void __bpf_prog_put_rcu(struct rcu_head *rcu)
{
struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
@@ -2056,7 +2032,7 @@ static void bpf_prog_put_deferred(struct work_struct *work)
* simply waiting for refcnt to drop to be freed.
*/
if (prog->aux->id) {
- bpf_prog_free_id(prog);
+ bpf_free_obj_id(prog->aux->obj_id, PROG_OBJ_ID);
prog->aux->id = 0;
}
__bpf_prog_put_noref(prog, true);
@@ -2157,7 +2133,7 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
prog->jited,
prog_tag,
prog->pages * 1ULL << PAGE_SHIFT,
- prog->aux->id,
+ bpf_obj_id_vnr(prog->aux->obj_id),
stats.nsecs,
stats.cnt,
stats.misses,
@@ -2468,6 +2444,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
enum bpf_prog_type type = attr->prog_type;
struct bpf_prog *prog, *dst_prog = NULL;
struct btf *attach_btf = NULL;
+ struct bpf_obj_id *obj_id;
int err;
char license[128];
bool is_gpl;
@@ -2621,12 +2598,13 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
if (err < 0)
goto free_used_maps;

- err = bpf_prog_alloc_id(prog);
- if (err < 0)
+ obj_id = bpf_alloc_obj_id(current->nsproxy->bpf_ns, prog, PROG_OBJ_ID);
+ if (IS_ERR(obj_id))
goto free_used_maps;
- prog->aux->id = err;
+ prog->aux->obj_id = obj_id;
+ prog->aux->id = bpf_obj_id_nr(obj_id);

- /* Upon success of bpf_prog_alloc_id(), the BPF prog is
+ /* Upon success of bpf_alloc_obj_id(), the BPF prog is
* effectively publicly exposed. However, retrieving via
* bpf_prog_get_fd_by_id() will take another reference,
* therefore it cannot be gone underneath us.
@@ -2803,7 +2781,7 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
"prog_tag:\t%s\n"
"prog_id:\t%u\n",
prog_tag,
- prog->aux->id);
+ bpf_obj_id_vnr(prog->aux->obj_id));
}
if (link->ops->show_fdinfo)
link->ops->show_fdinfo(link, m);
@@ -3706,11 +3684,12 @@ struct bpf_map *bpf_map_get_curr_or_next(u32 *id)

struct bpf_prog *bpf_prog_get_curr_or_next(u32 *id)
{
+ struct bpf_namespace *ns = current->nsproxy->bpf_ns;
struct bpf_prog *prog;

spin_lock_bh(&prog_idr_lock);
again:
- prog = idr_get_next(&prog_idr, id);
+ prog = idr_get_next(&ns->idr[PROG_OBJ_ID], id);
if (prog) {
prog = bpf_prog_inc_not_zero(prog);
if (IS_ERR(prog)) {
@@ -3727,13 +3706,14 @@ struct bpf_prog *bpf_prog_get_curr_or_next(u32 *id)

struct bpf_prog *bpf_prog_by_id(u32 id)
{
+ struct bpf_namespace *ns = current->nsproxy->bpf_ns;
struct bpf_prog *prog;

if (!id)
return ERR_PTR(-ENOENT);

spin_lock_bh(&prog_idr_lock);
- prog = idr_find(&prog_idr, id);
+ prog = idr_find(&ns->idr[PROG_OBJ_ID], id);
if (prog)
prog = bpf_prog_inc_not_zero(prog);
else
@@ -3939,7 +3919,7 @@ static int bpf_prog_get_info_by_fd(struct file *file,
return -EFAULT;

info.type = prog->type;
- info.id = prog->aux->id;
+ info.id = bpf_obj_id_vnr(prog->aux->obj_id);
info.load_time = prog->aux->load_time;
info.created_by_uid = from_kuid_munged(current_user_ns(),
prog->aux->user->uid);
@@ -4287,7 +4267,7 @@ static int bpf_link_get_info_by_fd(struct file *file,
info.type = link->type;
info.id = link->id;
if (link->prog)
- info.prog_id = link->prog->aux->id;
+ info.prog_id = bpf_obj_id_vnr(link->prog->aux->obj_id);

if (link->ops->fill_link_info) {
err = link->ops->fill_link_info(link, &info);
@@ -4452,7 +4432,7 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
struct bpf_raw_event_map *btp = raw_tp->btp;

err = bpf_task_fd_query_copy(attr, uattr,
- raw_tp->link.prog->aux->id,
+ bpf_obj_id_vnr(raw_tp->link.prog->aux->obj_id),
BPF_FD_TYPE_RAW_TRACEPOINT,
btp->tp->name, 0, 0);
goto put_file;
@@ -5048,7 +5028,7 @@ static int __sys_bpf(int cmd, bpfptr_t uattr, unsigned int size)
break;
case BPF_PROG_GET_NEXT_ID:
err = bpf_obj_get_next_id(&attr, uattr.user,
- &prog_idr, &prog_idr_lock);
+ &ns->idr[PROG_OBJ_ID], &prog_idr_lock);
break;
case BPF_MAP_GET_NEXT_ID:
err = bpf_obj_get_next_id(&attr, uattr.user,
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
index a71aef7..1fd8ceb 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
+++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
@@ -28,7 +28,8 @@ static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type)

switch (type) {
case BPF_OBJ_PROG:
- return BPF_CORE_READ((struct bpf_prog *)ent, aux, id);
+ obj_id = BPF_CORE_READ((struct bpf_prog *)ent, aux, obj_id);
+ break;
case BPF_OBJ_MAP:
obj_id = BPF_CORE_READ((struct bpf_map *)ent, obj_id);
break;
--
1.8.3.1

Next message: Yafang Shao: "[RFC PATCH bpf-next 11/13] bpf: Allow iterating bpf objects with CAP_BPF in bpf namespace"
Previous message: Yafang Shao: "[RFC PATCH bpf-next 08/13] bpf: Alloc and free bpf_map id in bpf namespace"
In reply to: Yafang Shao: "Re: [RFC PATCH bpf-next 08/13] bpf: Alloc and free bpf_map id in bpf namespace"
Next in thread: Yafang Shao: "[RFC PATCH bpf-next 11/13] bpf: Allow iterating bpf objects with CAP_BPF in bpf namespace"
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