From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomas Bortoli Subject: [V9fs-developer] [PATCH] p9_check_errors() validate PDU length Date: Tue, 10 Jul 2018 00:43:23 +0200 Message-ID: <20180709224323.20597-1-tomasbortoli@gmail.com> Cc: davem@davemloft.net, v9fs-developer@lists.sourceforge.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller@googlegroups.com, Tomas Bortoli To: ericvh@gmail.com, rminnich@sandia.gov, lucho@ionkov.net Return-path: Received: from mail-wm0-f65.google.com ([74.125.82.65]:35229 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933166AbeGIWn3 (ORCPT ); Mon, 9 Jul 2018 18:43:29 -0400 Sender: netdev-owner@vger.kernel.org List-ID: p9_check_errors() does not validate the size of the PDU read in p9_parse_header(). Any size can be passed, provoking out-of-bound reads. Signed-off-by: Tomas Bortoli Reported-by: syzbot+65c6b72f284a39d416b4@syzkaller.appspotmail.com --- As suggested by Dominique: https://lkml.org/lkml/2018/7/9/688 Such check is not enough as it will prevent to read more than how it has been allocated but it won't prevent to read more than how it has been read So this patch will require some more changes to prevent bad sizes. net/9p/client.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/9p/client.c b/net/9p/client.c index 40f7c47f2f74..5b161b576b8a 100644 --- a/net/9p/client.c +++ b/net/9p/client.c @@ -520,10 +520,13 @@ EXPORT_SYMBOL(p9_parse_header); static int p9_check_errors(struct p9_client *c, struct p9_req_t *req) { int8_t type; + int32_t size; int err; int ecode; - err = p9_parse_header(req->rc, NULL, &type, NULL, 0); + err = p9_parse_header(req->rc, &size, &type, NULL, 0); + if (size > req->rc->capacity) + return -EINVAL; /* * dump the response from server * This should be after check errors which poplulate pdu_fcall. -- 2.11.0