From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [PATCH net] sctp: make sure stream nums can match optlen in sctp_setsockopt_reset_streams Date: Mon, 11 Dec 2017 13:28:12 -0500 Message-ID: <20171211182812.GC18284@hmswarspite.think-freely.org> References: <20171211145434.GB18284@hmswarspite.think-freely.org> <20171211153639.GA3532@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Xin Long , network dev , linux-sctp@vger.kernel.org, davem@davemloft.net, syzkaller@googlegroups.com To: Marcelo Ricardo Leitner Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:46097 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752574AbdLKS3A (ORCPT ); Mon, 11 Dec 2017 13:29:00 -0500 Content-Disposition: inline In-Reply-To: <20171211153639.GA3532@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Dec 11, 2017 at 01:36:39PM -0200, Marcelo Ricardo Leitner wrote: > Hi, > > On Mon, Dec 11, 2017 at 09:54:34AM -0500, Neil Horman wrote: > > On Sun, Dec 10, 2017 at 03:40:51PM +0800, Xin Long wrote: > > > Now in sctp_setsockopt_reset_streams, it only does the check > > > optlen < sizeof(*params) for optlen. But it's not enough, as > > > params->srs_number_streams should also match optlen. > > > > > > If the streams in params->srs_stream_list are less than stream > > > nums in params->srs_number_streams, later when dereferencing > > > the stream list, it could cause a slab-out-of-bounds crash, as > > > reported by syzbot. > > > > > > This patch is to fix it by also checking the stream numbers in > > > sctp_setsockopt_reset_streams to make sure at least it's not > > > greater than the streams in the list. > > > > > > Fixes: 7f9d68ac944e ("sctp: implement sender-side procedures for SSN Reset Request Parameter") > > > Reported-by: Dmitry Vyukov > > > Signed-off-by: Xin Long > > > --- > > > net/sctp/socket.c | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > > > index 014847e..dbf140d 100644 > > > --- a/net/sctp/socket.c > > > +++ b/net/sctp/socket.c > > > @@ -3891,13 +3891,17 @@ static int sctp_setsockopt_reset_streams(struct sock *sk, > > > struct sctp_association *asoc; > > > int retval = -EINVAL; > > > > > > - if (optlen < sizeof(struct sctp_reset_streams)) > > > + if (optlen < sizeof(*params)) > > > return -EINVAL; > > > > > Is this going to work in all corner cases? IIRC struct > > sctp_reset_stream has variable length array at the end of it, and so > > sizeof(struct sctp_reset_streams) returns just the size of the > > struct, while sizeof(*params) returns the size of the entire object > > (including the array elements). If a user space task allocates a > > I don't think it can include the array elements as such information > can't be passed from the application to the kernel other than via > optlen parameter. There is no metadata around the struct that could > allow that, and sizeof() is a constant, it can't be assuming different > values in runtime. > > Cheers, > Marcelo >% Yup, you're right, its fine. Acked-by: Neil Horman > > static memory block to hold this struct and the array, and passes it > > in with a shorter optlen (if for example, they do not intend to use > > all the array elements), this will cause a failure, where no failure > > is truly warranted. It seems the correct check to me should be the > > origional sizeof(struct sctp_reset_streams) check, and the below > > check to ensure that there are at least the same number of array > > elements available as indicated in srs_nuber_streams. > > > > Regards > > Neil > > > > > params = memdup_user(optval, optlen); > > > if (IS_ERR(params)) > > > return PTR_ERR(params); > > > > > > + if (params->srs_number_streams * sizeof(__u16) > > > > + optlen - sizeof(*params)) > > > + goto out; > > > + > > > asoc = sctp_id2assoc(sk, params->srs_assoc_id); > > > if (!asoc) > > > goto out; > > > -- > > > 2.1.0 > > > > > > -- > > > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > > > the body of a message to majordomo@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >