From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Subject: Re: [PATCH net] sctp: check stream reset info len before making reconf chunk Date: Tue, 14 Nov 2017 17:06:54 -0200 Message-ID: <20171114190349.GI3675@localhost.localdomain> References: <9ad1a0713999f4771e6f1050f4d17dc2d9ab1fe8.1510551567.git.lucien.xin@gmail.com> <20171113150934.GB7876@hmswarspite.think-freely.org> <20171113195402.GG3675@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Neil Horman , network dev , linux-sctp@vger.kernel.org, davem , Dmitry Vyukov , syzkaller To: Xin Long Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32916 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754400AbdKNTG7 (ORCPT ); Tue, 14 Nov 2017 14:06:59 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Nov 14, 2017 at 04:27:41PM +0800, Xin Long wrote: > On Tue, Nov 14, 2017 at 3:54 AM, Marcelo Ricardo Leitner > wrote: > > On Mon, Nov 13, 2017 at 11:15:40PM +0800, Xin Long wrote: > >> On Mon, Nov 13, 2017 at 11:09 PM, Neil Horman wrote: > >> > On Mon, Nov 13, 2017 at 01:39:27PM +0800, Xin Long wrote: > >> >> Now when resetting stream, if both in and out flags are set, the info > >> >> len can reach: > >> >> sizeof(struct sctp_strreset_outreq) + SCTP_MAX_STREAM(65535) + > >> >> sizeof(struct sctp_strreset_inreq) + SCTP_MAX_STREAM(65535) > >> >> even without duplicated stream no, this value is far greater than the > >> >> chunk's max size. > >> >> > >> >> _sctp_make_chunk doesn't do any check for this, which would cause the > >> >> skb it allocs is huge, syzbot even reported a crash due to this. > >> >> > >> >> This patch is to check stream reset info len before making reconf > >> >> chunk and return NULL if the len exceeds chunk's capacity. > >> >> > >> >> Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk") > >> >> Reported-by: Dmitry Vyukov > >> >> Signed-off-by: Xin Long > >> >> --- > >> >> net/sctp/sm_make_chunk.c | 7 +++++-- > >> >> net/sctp/stream.c | 8 +++++--- > >> >> 2 files changed, 10 insertions(+), 5 deletions(-) > >> >> > >> >> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c > >> >> index 514465b..a21328a 100644 > >> >> --- a/net/sctp/sm_make_chunk.c > >> >> +++ b/net/sctp/sm_make_chunk.c > >> >> @@ -3598,14 +3598,17 @@ struct sctp_chunk *sctp_make_strreset_req( > >> >> __u16 stream_len = stream_num * 2; > > > > Unrelated, but.. won't stream_len overflow if stream_num >= 32768? > > When called form sctp_send_reset_streams() I don't see anything > > restricting it to such range. > right. > > > > >> >> struct sctp_strreset_inreq inreq; > >> >> struct sctp_chunk *retval; > >> >> - __u16 outlen, inlen; > >> >> + int outlen, inlen; > >> >> > >> >> outlen = (sizeof(outreq) + stream_len) * out; > >> >> inlen = (sizeof(inreq) + stream_len) * in; > >> >> > >> >> + if (outlen + inlen > SCTP_MAX_CHUNK_LEN - sizeof(struct sctp_chunkhdr)) > >> >> + return ERR_PTR(-EINVAL); > >> >> + > >> > Why all the ERR_PTR manipulations here? Just returning NULL, like the fuction > >> > has been doing is sufficient to set ENOMEM at both call sites > >> I don't like ERR_PTR handling here either, > >> But it shouldn't be ENOMEM, should it ? > >> > >> It may confuse users, but I'm also ok to let it just return > >> ENOMEM as you wish. wdyt ? > > > > Returning ENOMEM in the above error can be misleading. It's not that > > we cannot allocate it, it's that it won't fit the packet no matter how > > much memory we add to the system. > right. > > let's move the check into sctp_send_reset_streams() > > I believe this one fixes them both: > @@ -139,15 +139,31 @@ int sctp_send_reset_streams(struct sctp_association *asoc, > > str_nums = params->srs_number_streams; > str_list = params->srs_stream_list; > - if (out && str_nums) > - for (i = 0; i < str_nums; i++) > - if (str_list[i] >= stream->outcnt) > - goto out; > + if (str_nums) { > + int param_len = 0; > > - if (in && str_nums) > - for (i = 0; i < str_nums; i++) > - if (str_list[i] >= stream->incnt) > - goto out; > + if (out) { > + for (i = 0; i < str_nums; i++) > + if (str_list[i] >= stream->outcnt) > + goto out; > + > + param_len = str_nums * 2 + sizeof(__u16) --^ > + sizeof(struct sctp_strreset_outreq); > + } > + > + if (in) { > + for (i = 0; i < str_nums; i++) > + if (str_list[i] >= stream->incnt) > + goto out; > + > + param_len += str_nums * 2 + sizeof(__u16) --^ > + sizeof(struct sctp_strreset_inreq); > + } > + > + if (param_len > SCTP_MAX_CHUNK_LEN - > + sizeof(struct sctp_reconf_chunk)) > + goto out; > + } > > > and int this fix, it's good to do all checks only when str_nums !=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 > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Date: Tue, 14 Nov 2017 19:06:54 +0000 Subject: Re: [PATCH net] sctp: check stream reset info len before making reconf chunk Message-Id: <20171114190349.GI3675@localhost.localdomain> List-Id: References: <9ad1a0713999f4771e6f1050f4d17dc2d9ab1fe8.1510551567.git.lucien.xin@gmail.com> <20171113150934.GB7876@hmswarspite.think-freely.org> <20171113195402.GG3675@localhost.localdomain> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Xin Long Cc: Neil Horman , network dev , linux-sctp@vger.kernel.org, davem , Dmitry Vyukov , syzkaller On Tue, Nov 14, 2017 at 04:27:41PM +0800, Xin Long wrote: > On Tue, Nov 14, 2017 at 3:54 AM, Marcelo Ricardo Leitner > wrote: > > On Mon, Nov 13, 2017 at 11:15:40PM +0800, Xin Long wrote: > >> On Mon, Nov 13, 2017 at 11:09 PM, Neil Horman wrote: > >> > On Mon, Nov 13, 2017 at 01:39:27PM +0800, Xin Long wrote: > >> >> Now when resetting stream, if both in and out flags are set, the info > >> >> len can reach: > >> >> sizeof(struct sctp_strreset_outreq) + SCTP_MAX_STREAM(65535) + > >> >> sizeof(struct sctp_strreset_inreq) + SCTP_MAX_STREAM(65535) > >> >> even without duplicated stream no, this value is far greater than the > >> >> chunk's max size. > >> >> > >> >> _sctp_make_chunk doesn't do any check for this, which would cause the > >> >> skb it allocs is huge, syzbot even reported a crash due to this. > >> >> > >> >> This patch is to check stream reset info len before making reconf > >> >> chunk and return NULL if the len exceeds chunk's capacity. > >> >> > >> >> Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk") > >> >> Reported-by: Dmitry Vyukov > >> >> Signed-off-by: Xin Long > >> >> --- > >> >> net/sctp/sm_make_chunk.c | 7 +++++-- > >> >> net/sctp/stream.c | 8 +++++--- > >> >> 2 files changed, 10 insertions(+), 5 deletions(-) > >> >> > >> >> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c > >> >> index 514465b..a21328a 100644 > >> >> --- a/net/sctp/sm_make_chunk.c > >> >> +++ b/net/sctp/sm_make_chunk.c > >> >> @@ -3598,14 +3598,17 @@ struct sctp_chunk *sctp_make_strreset_req( > >> >> __u16 stream_len = stream_num * 2; > > > > Unrelated, but.. won't stream_len overflow if stream_num >= 32768? > > When called form sctp_send_reset_streams() I don't see anything > > restricting it to such range. > right. > > > > >> >> struct sctp_strreset_inreq inreq; > >> >> struct sctp_chunk *retval; > >> >> - __u16 outlen, inlen; > >> >> + int outlen, inlen; > >> >> > >> >> outlen = (sizeof(outreq) + stream_len) * out; > >> >> inlen = (sizeof(inreq) + stream_len) * in; > >> >> > >> >> + if (outlen + inlen > SCTP_MAX_CHUNK_LEN - sizeof(struct sctp_chunkhdr)) > >> >> + return ERR_PTR(-EINVAL); > >> >> + > >> > Why all the ERR_PTR manipulations here? Just returning NULL, like the fuction > >> > has been doing is sufficient to set ENOMEM at both call sites > >> I don't like ERR_PTR handling here either, > >> But it shouldn't be ENOMEM, should it ? > >> > >> It may confuse users, but I'm also ok to let it just return > >> ENOMEM as you wish. wdyt ? > > > > Returning ENOMEM in the above error can be misleading. It's not that > > we cannot allocate it, it's that it won't fit the packet no matter how > > much memory we add to the system. > right. > > let's move the check into sctp_send_reset_streams() > > I believe this one fixes them both: > @@ -139,15 +139,31 @@ int sctp_send_reset_streams(struct sctp_association *asoc, > > str_nums = params->srs_number_streams; > str_list = params->srs_stream_list; > - if (out && str_nums) > - for (i = 0; i < str_nums; i++) > - if (str_list[i] >= stream->outcnt) > - goto out; > + if (str_nums) { > + int param_len = 0; > > - if (in && str_nums) > - for (i = 0; i < str_nums; i++) > - if (str_list[i] >= stream->incnt) > - goto out; > + if (out) { > + for (i = 0; i < str_nums; i++) > + if (str_list[i] >= stream->outcnt) > + goto out; > + > + param_len = str_nums * 2 + sizeof(__u16) --^ > + sizeof(struct sctp_strreset_outreq); > + } > + > + if (in) { > + for (i = 0; i < str_nums; i++) > + if (str_list[i] >= stream->incnt) > + goto out; > + > + param_len += str_nums * 2 + sizeof(__u16) --^ > + sizeof(struct sctp_strreset_inreq); > + } > + > + if (param_len > SCTP_MAX_CHUNK_LEN - > + sizeof(struct sctp_reconf_chunk)) > + goto out; > + } > > > and int this fix, it's good to do all checks only when str_nums !=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 >