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Date: Tue, 2 Nov 2021 13:11:11 -0700
From: Yonghong Song <yhs@...com>
To: Di Zhu <zhudi2@...wei.com>, <davem@...emloft.net>,
<ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
<kafai@...com>, <songliubraving@...com>,
<john.fastabend@...il.com>, <kpsingh@...nel.org>,
<jakub@...udflare.com>
CC: <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs
attached to sockmap
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@...wei.com>
> ---
> 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) {
>
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