4.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Xin Long <lucien.xin@xxxxxxxxx>
[ 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@xxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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); \