linux.git/net/sctp/protocol.c, branch v5.12

sctp: bring inet(6)_skb_parm back to sctp_input_cb

2020-11-05T22:27:30+00:00

inet(6)_skb_parm was removed from sctp_input_cb by Commit a1dd2cf2f1ae
("sctp: allow changing transport encap_port by peer packets"), as it
thought sctp_input_cb->header is not used any more in SCTP.

syzbot reported a crash:

  [ ] BUG: KASAN: use-after-free in decode_session6+0xe7c/0x1580
  [ ]
  [ ] Call Trace:
  [ ]  
  [ ]  dump_stack+0x107/0x163
  [ ]  kasan_report.cold+0x1f/0x37
  [ ]  decode_session6+0xe7c/0x1580
  [ ]  __xfrm_policy_check+0x2fa/0x2850
  [ ]  sctp_rcv+0x12b0/0x2e30
  [ ]  sctp6_rcv+0x22/0x40
  [ ]  ip6_protocol_deliver_rcu+0x2e8/0x1680
  [ ]  ip6_input_finish+0x7f/0x160
  [ ]  ip6_input+0x9c/0xd0
  [ ]  ipv6_rcv+0x28e/0x3c0

It was caused by sctp_input_cb->header/IP6CB(skb) still used in sctp rx
path decode_session6() but some members overwritten by sctp6_rcv().

This patch is to fix it by bring inet(6)_skb_parm back to sctp_input_cb
and not overwriting it in sctp4/6_rcv() and sctp_udp_rcv().

Reported-by: syzbot+5be8aebb1b7dfa90ef31@syzkaller.appspotmail.com
Fixes: a1dd2cf2f1ae ("sctp: allow changing transport encap_port by peer packets")
Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Link: https://lore.kernel.org/r/136c1a7a419341487c504be6d1996928d9d16e02.1604472932.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski

sctp: support for sending packet over udp4 sock

2020-10-30T22:24:30+00:00

This patch does what the rfc6951#section-5.3 says for ipv4:

  "Within the UDP header, the source port MUST be the local UDP
   encapsulation port number of the SCTP stack, and the destination port
   MUST be the remote UDP encapsulation port number maintained for the
   association and the destination address to which the packet is sent
   (see Section 5.1).

   Because the SCTP packet is the UDP payload, the length of the UDP
   packet MUST be the length of the SCTP packet plus the size of the UDP
   header.

   The SCTP checksum MUST be computed for IPv4 and IPv6, and the UDP
   checksum SHOULD be computed for IPv4 and IPv6."

Some places need to be adjusted in sctp_packet_transmit():

  1. For non-gso packets, when transport's encap_port is set, sctp
     checksum has to be done in sctp_packet_pack(), as the outer
     udp will use ip_summed = CHECKSUM_PARTIAL to do the offload
     setting for checksum.

  2. Delay calling dst_clone() and skb_dst_set() for non-udp packets
     until sctp_v4_xmit(), as for udp packets, skb_dst_set() is not
     needed before calling udp_tunnel_xmit_skb().

then in sctp_v4_xmit():

  1. Go to udp_tunnel_xmit_skb() only when transport->encap_port and
     net->sctp.udp_port both are set, as these are one for dst port
     and another for src port.

  2. For gso packet, SKB_GSO_UDP_TUNNEL_CSUM is set for gso_type, and
     with this udp checksum can be done in __skb_udp_tunnel_segment()
     for each segments after the sctp gso.

  3. inner_mac_header and inner_transport_header are set, as these
     will be needed in __skb_udp_tunnel_segment() to find the right
     headers.

  4. df and ttl are calculated, as these are the required params by
     udp_tunnel_xmit_skb().

  5. nocheck param has to be false, as "the UDP checksum SHOULD be
     computed for IPv4 and IPv6", says in rfc6951#section-5.3.

v1->v2:
  - Use sp->udp_port instead in sctp_v4_xmit(), which is more safe.

Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: Jakub Kicinski

sctp: allow changing transport encap_port by peer packets

2020-10-30T22:24:16+00:00

As rfc6951#section-5.4 says:

  "After finding the SCTP association (which
   includes checking the verification tag), the UDP source port MUST be
   stored as the encapsulation port for the destination address the SCTP
   packet is received from (see Section 5.1).

   When a non-encapsulated SCTP packet is received by the SCTP stack,
   the encapsulation of outgoing packets belonging to the same
   association and the corresponding destination address MUST be
   disabled."

transport encap_port should be updated by a validated incoming packet's
udp src port.

We save the udp src port in sctp_input_cb->encap_port, and then update
the transport in two places:

  1. right after vtag is verified, which is required by RFC, and this
     allows the existent transports to be updated by the chunks that
     can only be processed on an asoc.

  2. right before processing the 'init' where the transports are added,
     and this allows building a sctp over udp connection by client with
     the server not knowing the remote encap port.

  3. when processing ootb_pkt and creating the temporary transport for
     the reply pkt.

Note that sctp_input_cb->header is removed, as it's not used any more
in sctp.

v1->v2:
  - Change encap_port as __be16 for sctp_input_cb.

Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: Jakub Kicinski

sctp: add encap_port for netns sock asoc and transport

2020-10-30T22:24:06+00:00

encap_port is added as per netns/sock/assoc/transport, and the
latter one's encap_port inherits the former one's by default.
The transport's encap_port value would mostly decide if one
packet should go out with udp encapsulated or not.

This patch also allows users to set netns' encap_port by sysctl.

v1->v2:
  - Change to define encap_port as __be16 for sctp_sock, asoc and
    transport.
v2->v3:
  - No change.
v3->v4:
  - Add 'encap_port' entry in ip-sysctl.rst.
v4->v5:
  - Improve the description of encap_port in ip-sysctl.rst.

Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: Jakub Kicinski

sctp: add encap_err_lookup for udp encap socks

2020-10-30T22:24:00+00:00

As it says in rfc6951#section-5.5:

  "When receiving ICMP or ICMPv6 response packets, there might not be
   enough bytes in the payload to identify the SCTP association that the
   SCTP packet triggering the ICMP or ICMPv6 packet belongs to.  If a
   received ICMP or ICMPv6 packet cannot be related to a specific SCTP
   association or the verification tag cannot be verified, it MUST be
   discarded silently.  In particular, this means that the SCTP stack
   MUST NOT rely on receiving ICMP or ICMPv6 messages.  Implementation
   constraints could prevent processing received ICMP or ICMPv6
   messages."

ICMP or ICMPv6 packets need to be handled, and this is implemented by
udp encap sock .encap_err_lookup function.

The .encap_err_lookup function is called in __udp(6)_lib_err_encap()
to confirm this path does need to be updated. For sctp, what we can
do here is check if the corresponding asoc and transport exist.

Note that icmp packet process for sctp over udp is done by udp sock
.encap_err_lookup(), and it means for now we can't do as much as
sctp_v4/6_err() does. Also we can't do the two mappings mentioned
in rfc6951#section-5.5.

Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: Jakub Kicinski

sctp: create udp6 sock and set its encap_rcv

2020-10-30T22:23:56+00:00

This patch is to add the udp6 sock part in sctp_udp_sock_start/stop().
udp_conf.use_udp6_rx_checksums is set to true, as:

   "The SCTP checksum MUST be computed for IPv4 and IPv6, and the UDP
    checksum SHOULD be computed for IPv4 and IPv6"

says in rfc6951#section-5.3.

v1->v2:
  - Add pr_err() when fails to create udp v6 sock.
  - Add #if IS_ENABLED(CONFIG_IPV6) not to create v6 sock when ipv6 is
    disabled.

Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: Jakub Kicinski

sctp: create udp4 sock and add its encap_rcv

2020-10-30T22:23:52+00:00

This patch is to add the functions to create/release udp4 sock,
and set the sock's encap_rcv to process the incoming udp encap
sctp packets. In sctp_udp_rcv(), as we can see, all we need to
do is fix the transport header for sctp_rcv(), then it would
implement the part of rfc6951#section-5.4:

  "When an encapsulated packet is received, the UDP header is removed.
   Then, the generic lookup is performed, as done by an SCTP stack
   whenever a packet is received, to find the association for the
   received SCTP packet"

Note that these functions will be called in the last patch of
this patchset when enabling this feature.

v1->v2:
  - Add pr_err() when fails to create udp v4 sock.
v2->v3:
  - Add 'select NET_UDP_TUNNEL' in sctp Kconfig.
v3->v4:
  - No change.
v4->v5:
  - Change to set udp_port to 0 by default.

Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: Jakub Kicinski

net: sctp: protocol.c: delete duplicated words + punctuation

2020-08-24T23:21:43+00:00

Drop the repeated words "of" and "that".
Add some punctuation for readability.

Signed-off-by: Randy Dunlap 
Cc: Vlad Yasevich 
Cc: Neil Horman 
Cc: Marcelo Ricardo Leitner 
Cc: linux-sctp@vger.kernel.org
Cc: "David S. Miller" 
Cc: Jakub Kicinski 
Signed-off-by: David S. Miller

sctp: remove redundant initialization of variable status

2020-07-25T00:10:13+00:00

The variable status is being initialized with a value that is never read
and it is being updated later with a new value.  The initialization is
redundant and can be removed.  Also put the variable declarations into
reverse christmas tree order.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King 
Acked-by: Marcelo Ricardo Leitner 
Signed-off-by: David S. Miller

net/ipv4: remove compat_ip_{get,set}sockopt

2020-07-20T01:16:41+00:00

Handle the few cases that need special treatment in-line using
in_compat_syscall().

Signed-off-by: Christoph Hellwig 
Signed-off-by: David S. Miller