Patch "sctp: fix the check for _sctp_walk_params and _sctp_walk_errors" has been added to the 4.4-stable tree

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 4.4-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-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
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 <[email protected]>

[ 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.

---
 include/net/sctp/sctp.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -444,7 +444,7 @@ _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);\

@@ -456,7 +456,7 @@ _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 [email protected] are

queue-4.4/sctp-fix-the-check-for-_sctp_walk_params-and-_sctp_walk_errors.patch queue-4.4/dccp-fix-a-memleak-that-dccp_ipv6-doesn-t-put-reqsk-properly.patch queue-4.4/dccp-fix-a-memleak-that-dccp_ipv4-doesn-t-put-reqsk-properly.patch queue-4.4/dccp-fix-a-memleak-for-dccp_feat_init-err-process.patch