On Mon, Jan 13, 2020 at 11:23 PM CET, Martin Lau wrote:
> On Fri, Jan 10, 2020 at 11:50:20AM +0100, Jakub Sitnicki wrote:
>> Prepare for cloning listening sockets that have their protocol callbacks
>> overridden by sk_msg. Child sockets must not inherit parent callbacks that
>> access state stored in sk_user_data owned by the parent.
>>
>> Restore the child socket protocol callbacks before the it gets hashed and
>> any of the callbacks can get invoked.
>>
>> Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
>> ---
>> include/net/tcp.h | 1 +
>> net/ipv4/tcp_bpf.c | 13 +++++++++++++
>> net/ipv4/tcp_minisocks.c | 2 ++
>> 3 files changed, 16 insertions(+)
>>
>> diff --git a/include/net/tcp.h b/include/net/tcp.h
>> index 9dd975be7fdf..7cbf9465bb10 100644
>> --- a/include/net/tcp.h
>> +++ b/include/net/tcp.h
>> @@ -2181,6 +2181,7 @@ int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
>> int nonblock, int flags, int *addr_len);
>> int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
>> struct msghdr *msg, int len, int flags);
>> +void tcp_bpf_clone(const struct sock *sk, struct sock *child);
>>
>> /* Call BPF_SOCK_OPS program that returns an int. If the return value
>> * is < 0, then the BPF op failed (for example if the loaded BPF
>> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
>> index f6c83747c71e..6f96320fb7cf 100644
>> --- a/net/ipv4/tcp_bpf.c
>> +++ b/net/ipv4/tcp_bpf.c
>> @@ -586,6 +586,19 @@ static void tcp_bpf_close(struct sock *sk, long timeout)
>> saved_close(sk, timeout);
>> }
>>
>> +/* If a child got cloned from a listening socket that had tcp_bpf
>> + * protocol callbacks installed, we need to restore the callbacks to
>> + * the default ones because the child does not inherit the psock state
>> + * that tcp_bpf callbacks expect.
>> + */
>> +void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
>> +{
>> + struct proto *prot = newsk->sk_prot;
>> +
>> + if (prot->recvmsg == tcp_bpf_recvmsg)
> A question not related to this patch (may be it is more for patch 6).
>
> How tcp_bpf_recvmsg may be used for a listening sock (sk here)?
It can't be used. It's a way of checking if sock has tcp_bpf callbacks
that I copied from sk_psock_get_checked:
static inline struct sk_psock *sk_psock_get_checked(struct sock *sk)
{
struct sk_psock *psock;
rcu_read_lock();
psock = sk_psock(sk);
if (psock) {
if (sk->sk_prot->recvmsg != tcp_bpf_recvmsg) {
psock = ERR_PTR(-EBUSY);
goto out;
}
...
This makes me think that perhaps it deserves a well-named helper.
>
>> + newsk->sk_prot = sk->sk_prot_creator;
>> +}
>> +
