From mboxrd@z Thu Jan 1 00:00:00 1970 From: piaojun Subject: Re: [V9fs-developer] [PATCH] p9_check_errors() validate PDU length Date: Tue, 10 Jul 2018 09:31:10 +0800 Message-ID: <5B440C5E.2040909@huawei.com> References: <20180709224323.20597-1-tomasbortoli@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Cc: , , , , To: Tomas Bortoli , , , Return-path: In-Reply-To: <20180709224323.20597-1-tomasbortoli@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi Tomas, On 2018/7/10 6:43, Tomas Bortoli wrote: > 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; I think we should print some error logs here to remind uppper users. Thanks, Jun > /* > * dump the response from server > * This should be after check errors which poplulate pdu_fcall. >