Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap
From: Yonghong Song
Date: Tue Nov 02 2021 - 16:11:47 EST
On 11/2/21 1:48 AM, Di Zhu wrote:
Right now there is no way to query whether BPF programs are
attached to a sockmap or not.
we can use the standard interface in libbpf to query, such as:
bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
the mapFd is the fd of sockmap.
Signed-off-by: Di Zhu <zhudi2@xxxxxxxxxx>
---
include/linux/bpf.h | 9 +++++
kernel/bpf/syscall.c | 5 +++
net/core/sock_map.c | 88 ++++++++++++++++++++++++++++++++++++++++----
3 files changed, 95 insertions(+), 7 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d604c8251d88..594ca91992db 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags);
+int sockmap_bpf_prog_query(const union bpf_attr *attr,
+ union bpf_attr __user *uattr);
All previous functions are with prefix "sock_map". Why you choose
a different prefix "sockmap"?
+
void sock_map_unhash(struct sock *sk);
void sock_map_close(struct sock *sk, long timeout);
#else
@@ -2014,6 +2017,12 @@ static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
{
return -EOPNOTSUPP;
}
+
+static inline int sockmap_bpf_prog_query(const union bpf_attr *attr,
+ union bpf_attr __user *uattr)
+{
+ return -EINVAL;
+}
#endif /* CONFIG_BPF_SYSCALL */
#endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e50c0bfdb7d..17faeff8f85f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr *attr,
case BPF_FLOW_DISSECTOR:
case BPF_SK_LOOKUP:
return netns_bpf_prog_query(attr, uattr);
+ case BPF_SK_SKB_STREAM_PARSER:
+ case BPF_SK_SKB_STREAM_VERDICT:
+ case BPF_SK_MSG_VERDICT:
+ case BPF_SK_SKB_VERDICT:
+ return sockmap_bpf_prog_query(attr, uattr);
default:
return -EINVAL;
}
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index e252b8ec2b85..ca65ed0004d3 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1412,38 +1412,50 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
return NULL;
}
-static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
- struct bpf_prog *old, u32 which)
+static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog **pprog[],
Can we just change "**pprog[]" to "***pprog"? In the code, you really
just pass the address of the decl "struct bpf_prog **pprog;" to the
function.
+ u32 which)
Some format issue here?
{
struct sk_psock_progs *progs = sock_map_progs(map);
- struct bpf_prog **pprog;
if (!progs)
return -EOPNOTSUPP;
switch (which) {
case BPF_SK_MSG_VERDICT:
- pprog = &progs->msg_parser;
+ *pprog = &progs->msg_parser;
break;
#if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
case BPF_SK_SKB_STREAM_PARSER:
- pprog = &progs->stream_parser;
+ *pprog = &progs->stream_parser;
break;
#endif
case BPF_SK_SKB_STREAM_VERDICT:
if (progs->skb_verdict)
return -EBUSY;
- pprog = &progs->stream_verdict;
+ *pprog = &progs->stream_verdict;
break;
case BPF_SK_SKB_VERDICT:
if (progs->stream_verdict)
return -EBUSY;
- pprog = &progs->skb_verdict;
+ *pprog = &progs->skb_verdict;
break;
default:
return -EOPNOTSUPP;
}
+ return 0;
+}
+
+static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
+ struct bpf_prog *old, u32 which)
Some format issue here?
+{
+ struct bpf_prog **pprog;
+ int ret;
+
+ ret = sock_map_prog_lookup(map, &pprog, which);
+ if (ret)
+ return ret;
+
if (old)
return psock_replace_prog(pprog, prog, old);
@@ -1451,6 +1463,68 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
return 0;
}
+int sockmap_bpf_prog_query(const union bpf_attr *attr,
+ union bpf_attr __user *uattr)
Format issue here?
+{
+ __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
Typically we use u32 in the kernel code. But I know there are __u32
usage as well, esp. with __user attributes. I put a comment here just
in case that somebody else has a different opinion.
+ u32 prog_cnt = 0, flags = 0;
+ u32 ufd = attr->target_fd;
You can merge the above u32 together.
+ struct bpf_prog **pprog;
+ struct bpf_prog *prog;
+ struct bpf_map *map;
+ struct fd f;
+ int ret;
+ u32 id = 0;
to maintain reverse christmas tree?
+
+ if (attr->query.query_flags)
+ return -EINVAL;
+
+ f = fdget(ufd);
+ map = __bpf_map_get(f);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
+
+ rcu_read_lock();
+
+ ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type);
+ if (ret)
+ goto end;
+
+ prog = *pprog;
+ prog_cnt = (!prog) ? 0 : 1;
+
+ if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
+ goto end;
+
+ prog = bpf_prog_inc_not_zero(prog);
Could you explain why we need bpf_prog_inc_not_zero here?
We are inside rcu_read_lock/unlock region. We got a program
from *pprog. If this program is not NULL, this program should
not disappear since we are in rcu read lock region, right?
Maybe I missed something, it would be good you can explain
the scenario you try to pretect here.
+ if (IS_ERR(prog)) {
+ ret = PTR_ERR(prog);
+ goto end;
+ }
+ id = prog->aux->id;
+ bpf_prog_put(prog);
+
+end:
+ rcu_read_unlock();
+
+ if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
+ ret = -EFAULT;
+ goto err;
+ }
+ if (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) {
+ ret = -EFAULT;
+ goto err;
+ }
+ if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) {
+ ret = -EFAULT;
+ goto err;
+ }
You can do
if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)) ||
(id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) ||
copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
ret = -EFAULT;
to make code a little bit concise.
+
+err:
+ fdput(f);
+ return ret;
+}
+
static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
{
switch (link->map->map_type) {