| Message ID | 165030056960.5073.6664402939918720250.stgit@oracle-102.nfsv4.dev (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Implement a TLS handshake upcall | expand |
On 4/18/22 18:49, Chuck Lever wrote: > The sk_psock facility populates the sk_user_data field with the > address of an extra bit of metadata. User space sockets never > populate the sk_user_data field, so this has worked out fine. > > However, kernel consumers such as the RPC client and server do > populate the sk_user_data field. The sk_psock() function cannot tell > that the content of sk_user_data does not point to psock metadata, > so it will happily return a pointer to something else, cast to a > struct sk_psock. > > Thus kernel consumers and psock currently cannot co-exist. > > We could educate sk_psock() to return NULL if sk_user_data does > not point to a struct sk_psock. However, a more general solution > that enables full co-existence psock and other uses of sk_user_data > might be more interesting. > > Move the struct sk_psock address to its own pointer field so that > the contents of the sk_user_data field is preserved. > > Signed-off-by: Chuck Lever <chuck.lever@oracle.com> > --- > include/linux/skmsg.h | 2 +- > include/net/sock.h | 4 +++- > net/core/skmsg.c | 6 +++--- > 3 files changed, 7 insertions(+), 5 deletions(-) > Reviewed-by: Hannes Reinecke <hare@suse.de> Cheers, Hannes
>On 4/18/22 18:49, Chuck Lever wrote: >> The sk_psock facility populates the sk_user_data field with the >> address of an extra bit of metadata. User space sockets never >> populate the sk_user_data field, so this has worked out fine. >> >> However, kernel consumers such as the RPC client and server do >> populate the sk_user_data field. The sk_psock() function cannot tell >> that the content of sk_user_data does not point to psock metadata, >> so it will happily return a pointer to something else, cast to a >> struct sk_psock. >> >> Thus kernel consumers and psock currently cannot co-exist. >> >> We could educate sk_psock() to return NULL if sk_user_data does >> not point to a struct sk_psock. However, a more general solution >> that enables full co-existence psock and other uses of sk_user_data >> might be more interesting. >> >> Move the struct sk_psock address to its own pointer field so that >> the contents of the sk_user_data field is preserved. >> >> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> >> --- >> include/linux/skmsg.h | 2 +- >> include/net/sock.h | 4 +++- >> net/core/skmsg.c | 6 +++--- >> 3 files changed, 7 insertions(+), 5 deletions(-) >> >Reviewed-by: Hannes Reinecke <hare@suse.de> > >Cheers, > >Hannes In Patchwork website, this patch fails the checks on netdev/cc_maintainers. So maybe you need CC folks pointed out by scripts/get_maintainer.pl script, which is suggested by Jakub Kicinski <kuba@kernel.org>. What's more, Syskaller reports refcount bug in sk_psock_get (2). In this bug, the problem is that smc and psock, both use sk_user_data field to save their private data. So they will treat field in their own way. > in smc_switch_to_fallback(), and set smc->clcsock->sk_user_data > to origin smc in smc_fback_replace_callbacks(). > > Later, sk_psock_get() will treat the smc->clcsock->sk_user_data > as sk_psock type, which triggers the refcnt warning. I have tested this patch and the reproducer did not trigger any issue. For more details, you can check the email [PATCH] smc: fix refcount bug in sk_psock_get (2)
diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h index c5a2d6f50f25..5ef3a07c5b6c 100644 --- a/include/linux/skmsg.h +++ b/include/linux/skmsg.h @@ -277,7 +277,7 @@ static inline void sk_msg_sg_copy_clear(struct sk_msg *msg, u32 start) static inline struct sk_psock *sk_psock(const struct sock *sk) { - return rcu_dereference_sk_user_data(sk); + return rcu_dereference(sk->sk_psock); } static inline void sk_psock_set_state(struct sk_psock *psock, diff --git a/include/net/sock.h b/include/net/sock.h index c4b91fc19b9c..d2a513169527 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -327,7 +327,8 @@ struct sk_filter; * @sk_tskey: counter to disambiguate concurrent tstamp requests * @sk_zckey: counter to order MSG_ZEROCOPY notifications * @sk_socket: Identd and reporting IO signals - * @sk_user_data: RPC layer private data + * @sk_user_data: Upper layer private data + * @sk_psock: socket policy data (bpf) * @sk_frag: cached page frag * @sk_peek_off: current peek_offset value * @sk_send_head: front of stuff to transmit @@ -519,6 +520,7 @@ struct sock { struct socket *sk_socket; void *sk_user_data; + struct sk_psock __rcu *sk_psock; #ifdef CONFIG_SECURITY void *sk_security; #endif diff --git a/net/core/skmsg.c b/net/core/skmsg.c index cc381165ea08..2b3d01d92790 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -695,7 +695,7 @@ struct sk_psock *sk_psock_init(struct sock *sk, int node) write_lock_bh(&sk->sk_callback_lock); - if (sk->sk_user_data) { + if (sk->sk_psock) { psock = ERR_PTR(-EBUSY); goto out; } @@ -726,7 +726,7 @@ struct sk_psock *sk_psock_init(struct sock *sk, int node) sk_psock_set_state(psock, SK_PSOCK_TX_ENABLED); refcount_set(&psock->refcnt, 1); - rcu_assign_sk_user_data_nocopy(sk, psock); + rcu_assign_pointer(sk->sk_psock, psock); sock_hold(sk); out: @@ -825,7 +825,7 @@ void sk_psock_drop(struct sock *sk, struct sk_psock *psock) { write_lock_bh(&sk->sk_callback_lock); sk_psock_restore_proto(sk, psock); - rcu_assign_sk_user_data(sk, NULL); + rcu_assign_pointer(sk->sk_psock, NULL); if (psock->progs.stream_parser) sk_psock_stop_strp(sk, psock); else if (psock->progs.stream_verdict || psock->progs.skb_verdict)
The sk_psock facility populates the sk_user_data field with the address of an extra bit of metadata. User space sockets never populate the sk_user_data field, so this has worked out fine. However, kernel consumers such as the RPC client and server do populate the sk_user_data field. The sk_psock() function cannot tell that the content of sk_user_data does not point to psock metadata, so it will happily return a pointer to something else, cast to a struct sk_psock. Thus kernel consumers and psock currently cannot co-exist. We could educate sk_psock() to return NULL if sk_user_data does not point to a struct sk_psock. However, a more general solution that enables full co-existence psock and other uses of sk_user_data might be more interesting. Move the struct sk_psock address to its own pointer field so that the contents of the sk_user_data field is preserved. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> --- include/linux/skmsg.h | 2 +- include/net/sock.h | 4 +++- net/core/skmsg.c | 6 +++--- 3 files changed, 7 insertions(+), 5 deletions(-)