Patch "sctp: fix the check for _sctp_walk_params and _sctp_walk_errors" has been added to the 4.12-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    sctp: fix the check for _sctp_walk_params and _sctp_walk_errors

to the 4.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sctp-fix-the-check-for-_sctp_walk_params-and-_sctp_walk_errors.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Tue Aug  8 16:27:29 PDT 2017
From: Xin Long <lucien.xin@gmail.com>
Date: Wed, 26 Jul 2017 16:24:59 +0800
Subject: sctp: fix the check for _sctp_walk_params and _sctp_walk_errors

From: Xin Long <lucien.xin@gmail.com>


[ Upstream commit 6b84202c946cd3da3a8daa92c682510e9ed80321 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/sctp/sctp.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -469,7 +469,7 @@ _sctp_walk_params((pos), (chunk), ntohs(
 
 #define _sctp_walk_params(pos, chunk, end, member)\
 for (pos.v = chunk->member;\
-     (pos.v + offsetof(struct sctp_paramhdr, length) + sizeof(pos.p->length) <\
+     (pos.v + offsetof(struct sctp_paramhdr, length) + sizeof(pos.p->length) <=\
       (void *)chunk + end) &&\
      pos.v <= (void *)chunk + end - ntohs(pos.p->length) &&\
      ntohs(pos.p->length) >= sizeof(sctp_paramhdr_t);\
@@ -481,7 +481,7 @@ _sctp_walk_errors((err), (chunk_hdr), nt
 #define _sctp_walk_errors(err, chunk_hdr, end)\
 for (err = (sctp_errhdr_t *)((void *)chunk_hdr + \
 	    sizeof(sctp_chunkhdr_t));\
-     ((void *)err + offsetof(sctp_errhdr_t, length) + sizeof(err->length) <\
+     ((void *)err + offsetof(sctp_errhdr_t, length) + sizeof(err->length) <=\
       (void *)chunk_hdr + end) &&\
      (void *)err <= (void *)chunk_hdr + end - ntohs(err->length) &&\
      ntohs(err->length) >= sizeof(sctp_errhdr_t); \


Patches currently in stable-queue which might be from lucien.xin@gmail.com are

queue-4.12/sctp-fix-the-check-for-_sctp_walk_params-and-_sctp_walk_errors.patch
queue-4.12/dccp-fix-a-memleak-that-dccp_ipv6-doesn-t-put-reqsk-properly.patch
queue-4.12/dccp-fix-a-memleak-that-dccp_ipv4-doesn-t-put-reqsk-properly.patch
queue-4.12/dccp-fix-a-memleak-for-dccp_feat_init-err-process.patch
queue-4.12/sctp-fix-an-array-overflow-when-all-ext-chunks-are-set.patch