linux/net/sctp
Breno Leitao e1d001fa5b net: ioctl: Use kernel memory on protocol ioctl callbacks
Most of the ioctls to net protocols operates directly on userspace
argument (arg). Usually doing get_user()/put_user() directly in the
ioctl callback.  This is not flexible, because it is hard to reuse these
functions without passing userspace buffers.

Change the "struct proto" ioctls to avoid touching userspace memory and
operate on kernel buffers, i.e., all protocol's ioctl callbacks is
adapted to operate on a kernel memory other than on userspace (so, no
more {put,get}_user() and friends being called in the ioctl callback).

This changes the "struct proto" ioctl format in the following way:

    int                     (*ioctl)(struct sock *sk, int cmd,
-                                        unsigned long arg);
+                                        int *karg);

(Important to say that this patch does not touch the "struct proto_ops"
protocols)

So, the "karg" argument, which is passed to the ioctl callback, is a
pointer allocated to kernel space memory (inside a function wrapper).
This buffer (karg) may contain input argument (copied from userspace in
a prep function) and it might return a value/buffer, which is copied
back to userspace if necessary. There is not one-size-fits-all format
(that is I am using 'may' above), but basically, there are three type of
ioctls:

1) Do not read from userspace, returns a result to userspace
2) Read an input parameter from userspace, and does not return anything
  to userspace
3) Read an input from userspace, and return a buffer to userspace.

The default case (1) (where no input parameter is given, and an "int" is
returned to userspace) encompasses more than 90% of the cases, but there
are two other exceptions. Here is a list of exceptions:

* Protocol RAW:
   * cmd = SIOCGETVIFCNT:
     * input and output = struct sioc_vif_req
   * cmd = SIOCGETSGCNT
     * input and output = struct sioc_sg_req
   * Explanation: for the SIOCGETVIFCNT case, userspace passes the input
     argument, which is struct sioc_vif_req. Then the callback populates
     the struct, which is copied back to userspace.

* Protocol RAW6:
   * cmd = SIOCGETMIFCNT_IN6
     * input and output = struct sioc_mif_req6
   * cmd = SIOCGETSGCNT_IN6
     * input and output = struct sioc_sg_req6

* Protocol PHONET:
  * cmd == SIOCPNADDRESOURCE | SIOCPNDELRESOURCE
     * input int (4 bytes)
  * Nothing is copied back to userspace.

For the exception cases, functions sock_sk_ioctl_inout() will
copy the userspace input, and copy it back to kernel space.

The wrapper that prepare the buffer and put the buffer back to user is
sk_ioctl(), so, instead of calling sk->sk_prot->ioctl(), the callee now
calls sk_ioctl(), which will handle all cases.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230609152800.830401-1-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-06-15 22:33:26 -07:00
..
associola.c sctp: delete the nested flexible array peer_init 2023-04-21 08:19:30 +01:00
auth.c sctp: delete the nested flexible array hmac 2023-04-21 08:19:30 +01:00
bind_addr.c sctp: fail if no bound addresses can be used for a given scope 2023-01-24 18:32:33 -08:00
chunk.c net: sctp: chunk.c: delete duplicated word 2020-08-24 16:21:43 -07:00
debug.c sctp: add the probe timer in transport for PLPMTUD 2021-06-22 11:28:52 -07:00
diag.c sctp: sctp_sock_filter(): avoid list_entry() on possibly empty list 2023-02-10 19:28:29 -08:00
endpointola.c sctp: add dif and sdif check in asoc and ep lookup 2022-11-18 11:42:54 +00:00
input.c sctp: delete the nested flexible array params 2023-04-21 08:19:29 +01:00
inqueue.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 104 2019-05-24 17:39:00 +02:00
ipv6.c net: annotate lockless accesses to sk->sk_err_soft 2023-03-17 08:25:05 +00:00
Kconfig sctp: create udp4 sock and add its encap_rcv 2020-10-30 15:23:52 -07:00
Makefile sctp: add fair capacity stream scheduler 2023-03-09 11:31:44 +01:00
objcnt.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 104 2019-05-24 17:39:00 +02:00
offload.c net: move gso declarations and functions to their own files 2023-06-10 00:11:41 -07:00
output.c net: allow gso_max_size to exceed 65536 2022-05-16 10:18:55 +01:00
outqueue.c sctp: delete the nested flexible array variable 2023-04-21 08:19:29 +01:00
primitive.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 104 2019-05-24 17:39:00 +02:00
proc.c sctp: move hlist_node and hashent out of sctp_ep_common 2021-12-23 11:15:30 +00:00
protocol.c ipv4: Drop tos parameter from flowi4_update_output() 2023-06-02 10:52:38 +01:00
sm_make_chunk.c sctp: delete the nested flexible array peer_init 2023-04-21 08:19:30 +01:00
sm_sideeffect.c sctp: handle invalid error codes without calling BUG() 2023-06-12 09:36:27 +01:00
sm_statefuns.c sctp: fix an error code in sctp_sf_eat_auth() 2023-06-12 09:36:27 +01:00
sm_statetable.c sctp: add the probe timer in transport for PLPMTUD 2021-06-22 11:28:52 -07:00
socket.c net: ioctl: Use kernel memory on protocol ioctl callbacks 2023-06-15 22:33:26 -07:00
stream_interleave.c sctp: delete the nested flexible array skip 2023-04-21 08:19:29 +01:00
stream_sched_fc.c sctp: add weighted fair queueing stream scheduler 2023-03-09 11:31:44 +01:00
stream_sched_prio.c sctp: add a refcnt in sctp_stream_priorities to avoid a nested loop 2023-02-23 12:59:40 -08:00
stream_sched_rr.c sctp: delete free member from struct sctp_sched_ops 2022-12-01 20:14:23 -08:00
stream_sched.c sctp: fix a potential OOB access in sctp_sched_set_sched() 2023-05-10 12:10:15 +01:00
stream.c sctp: delete the nested flexible array params 2023-04-21 08:19:29 +01:00
sysctl.c sctp: sysctl: make extra pointers netns aware 2022-12-12 12:57:29 -08:00
transport.c sctp: fix an issue that plpmtu can never go to complete state 2023-05-22 11:05:20 +01:00
tsnmap.c net: sctp: trivial: fix typo in comment 2021-03-04 13:48:32 -08:00
ulpevent.c net: remove noblock parameter from recvmsg() entities 2022-04-12 15:00:25 +02:00
ulpqueue.c sctp: remove unnecessary NULL check in sctp_ulpq_tail_event() 2022-10-20 21:43:10 -07:00