sctp: fix the check for _sctp_walk_params and _sctp_walk_errors
authorXin Long <lucien.xin@gmail.com>
Wed, 26 Jul 2017 08:24:59 +0000 (16:24 +0800)
committerDavid S. Miller <davem@davemloft.net>
Thu, 27 Jul 2017 07:03:12 +0000 (00:03 -0700)
commit6b84202c946cd3da3a8daa92c682510e9ed80321
tree017fb69be1e7083df03315af8a40b5c42709ff0b
parente90ce2fc27cad7e7b1e72b9e66201a7a4c124c2b
sctp: fix the check for _sctp_walk_params and _sctp_walk_errors

Commit b1f5bfc27a19 ("sctp: don't dereference ptr before leaving
_sctp_walk_{params, errors}()") tried to fix the issue that it
may overstep the chunk end for _sctp_walk_{params, errors} with
'chunk_end > offset(length) + sizeof(length)'.

But it introduced a side effect: When processing INIT, it verifies
the chunks with 'param.v == chunk_end' after iterating all params
by sctp_walk_params(). With the check 'chunk_end > offset(length)
+ sizeof(length)', it would return when the last param is not yet
accessed. Because the last param usually is fwdtsn supported param
whose size is 4 and 'chunk_end == offset(length) + sizeof(length)'

This is a badly issue even causing sctp couldn't process 4-shakes.
Client would always get abort when connecting to server, due to
the failure of INIT chunk verification on server.

The patch is to use 'chunk_end <= offset(length) + sizeof(length)'
instead of 'chunk_end < offset(length) + sizeof(length)' for both
_sctp_walk_params and _sctp_walk_errors.

Fixes: b1f5bfc27a19 ("sctp: don't dereference ptr before leaving _sctp_walk_{params, errors}()")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/net/sctp/sctp.h