Ocfs2 devel - May 2020 - is it ok to always pull in sctp for dlm, was: Re: [PATCH 27/33] sctp: export sctp_setsockopt_bindx

On Wed, May 13, 2020 at 08:26:42AM +0200, Christoph Hellwig
wrote:
> And call it directly from dlm instead of going through kernel_setsockopt.
The advantage on using kernel_setsockopt here is that sctp module will
only be loaded if dlm actually creates a SCTP socket.  With this
change, sctp will be loaded on setups that may not be actually using
it. It's a quite big module and might expose the system.

I'm okay with the SCTP changes, but I'll defer to DLM folks to whether
that's too bad or what for DLM.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  fs/dlm/lowcomms.c       | 13 ++++++++-----
>  include/net/sctp/sctp.h |  3 +++
>  net/sctp/socket.c       |  5 +++--
>  3 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
> index b722a09a7ca05..e4939d770df53 100644
> --- a/fs/dlm/lowcomms.c
> +++ b/fs/dlm/lowcomms.c
> @@ -1005,14 +1005,17 @@ static int sctp_bind_addrs(struct connection *con,
uint16_t port)
>  		memcpy(&localaddr, dlm_local_addr[i], sizeof(localaddr));
>  		make_sockaddr(&localaddr, port, &addr_len);
>  
> -		if (!i)
> +		if (!i) {
>  			result = kernel_bind(con->sock,
>  					     (struct sockaddr *)&localaddr,
>  					     addr_len);
> -		else
> -			result = kernel_setsockopt(con->sock, SOL_SCTP,
> -						   SCTP_SOCKOPT_BINDX_ADD,
> -						   (char *)&localaddr, addr_len);
> +		} else {
> +			lock_sock(con->sock->sk);
> +			result = sctp_setsockopt_bindx(con->sock->sk,
> +					(struct sockaddr *)&localaddr, addr_len,
> +					SCTP_BINDX_ADD_ADDR);
> +			release_sock(con->sock->sk);
> +		}
>  
>  		if (result < 0) {
>  			log_print("Can't bind to %d addr number %d, %d.\n",
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index 3ab5c6bbb90bd..f702b14d768ba 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -615,4 +615,7 @@ static inline bool sctp_newsk_ready(const struct sock
*sk)
>  	return sock_flag(sk, SOCK_DEAD) || sk->sk_socket;
>  }
>  
> +int sctp_setsockopt_bindx(struct sock *sk, struct sockaddr *kaddrs,
> +		int addrs_size, int op);
> +
>  #endif /* __net_sctp_h__ */
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 1c96b52c4aa28..30c981d9f6158 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -979,8 +979,8 @@ int sctp_asconf_mgmt(struct sctp_sock *sp, struct
sctp_sockaddr_entry *addrw)
>   *
>   * Returns 0 if ok, <0 errno code on error.
>   */
> -static int sctp_setsockopt_bindx(struct sock *sk, struct sockaddr *kaddrs,
> -				 int addrs_size, int op)
> +int sctp_setsockopt_bindx(struct sock *sk, struct sockaddr *kaddrs,
> +		int addrs_size, int op)
>  {
>  	int err;
>  	int addrcnt = 0;
> @@ -1032,6 +1032,7 @@ static int sctp_setsockopt_bindx(struct sock *sk,
struct sockaddr *kaddrs,
>  		return -EINVAL;
>  	}
>  }
> +EXPORT_SYMBOL(sctp_setsockopt_bindx);
>  
>  static int sctp_connect_new_asoc(struct sctp_endpoint *ep,
>  				 const union sctp_addr *daddr,
> -- 
> 2.26.2
>

On Wed, May 13, 2020 at 03:00:58PM -0300, Marcelo Ricardo Leitner
wrote:
> On Wed, May 13, 2020 at 08:26:42AM +0200, Christoph Hellwig wrote:
> > And call it directly from dlm instead of going through
kernel_setsockopt.
> 
> The advantage on using kernel_setsockopt here is that sctp module will
> only be loaded if dlm actually creates a SCTP socket.  With this
> change, sctp will be loaded on setups that may not be actually using
> it. It's a quite big module and might expose the system.
True.  Not that the intent is to kill kernel space callers of setsockopt,
as I plan to remove the set_fs address space override used for it.  So
if always pulling in sctp is not an option for the DLM maintainers we'd
have to do tricks using symbol_get() or similar.

The same would also apply for ipv6, although I'm not sure how common
modular ipv6 is in practice.

From: Marcelo Ricardo Leitner
> Sent: 13 May 2020 19:01
> On Wed, May 13, 2020 at 08:26:42AM +0200, Christoph Hellwig wrote:
> > And call it directly from dlm instead of going through
kernel_setsockopt.
> 
> The advantage on using kernel_setsockopt here is that sctp module will
> only be loaded if dlm actually creates a SCTP socket.  With this
> change, sctp will be loaded on setups that may not be actually using
> it. It's a quite big module and might expose the system.
> 
> I'm okay with the SCTP changes, but I'll defer to DLM folks to
whether
> that's too bad or what for DLM.
I didn't see these sneak through.

There is a big long list of SCTP socket options that are
needed to make anything work.

They all need exporting.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT,
UK
Registration No: 1397386 (Wales)

On Wed, May 13, 2020 at 03:00:58PM -0300, Marcelo Ricardo Leitner
wrote:
> On Wed, May 13, 2020 at 08:26:42AM +0200, Christoph Hellwig wrote:
> > And call it directly from dlm instead of going through
kernel_setsockopt.
> 
> The advantage on using kernel_setsockopt here is that sctp module will
> only be loaded if dlm actually creates a SCTP socket.  With this
> change, sctp will be loaded on setups that may not be actually using
> it. It's a quite big module and might expose the system.
> 
> I'm okay with the SCTP changes, but I'll defer to DLM folks to
whether
> that's too bad or what for DLM.
So for ipv6 I could just move the helpers inline as they were trivial
and avoid that issue.  But some of the sctp stuff really is way too
big for that, so the only other option would be to use symbol_get.

Christoph Hellwig <hch at lst.de> wrote:
> > The advantage on using kernel_setsockopt here is that sctp module will
> > only be loaded if dlm actually creates a SCTP socket.  With this
> > change, sctp will be loaded on setups that may not be actually using
> > it. It's a quite big module and might expose the system.
> 
> True.  Not that the intent is to kill kernel space callers of setsockopt,
> as I plan to remove the set_fs address space override used for it.
For getsockopt, does it make sense to have the core kernel load optval/optlen
into a buffer before calling the protocol driver?  Then the driver need not
see the userspace pointer at all.

Similar could be done for setsockopt - allocate a buffer of the size requested
by the user inside the kernel and pass it into the driver, then copy the data
back afterwards.

David