On Mon, Nov 13, 2017 at 11:09 PM, Neil Horman <nhorman@xxxxxxxxxxxxx> 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 <dvyukov@xxxxxxxxxx>
>> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
>> ---
>> 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;
>> 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 ?
>
> Neil
>
>> retval = sctp_make_reconf(asoc, outlen + inlen);
>> if (!retval)
>> - return NULL;
>> + return ERR_PTR(-ENOMEM);
>>
>> if (outlen) {
>> outreq.param_hdr.type = SCTP_PARAM_RESET_OUT_REQUEST;
>> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
>> index fa8371f..51a25bf 100644
>> --- a/net/sctp/stream.c
>> +++ b/net/sctp/stream.c
>> @@ -162,8 +162,8 @@ int sctp_send_reset_streams(struct sctp_association *asoc,
>>
>> kfree(nstr_list);
>>
>> - if (!chunk) {
>> - retval = -ENOMEM;
>> + if (IS_ERR(chunk)) {
>> + retval = PTR_ERR(chunk);
>> goto out;
>> }
>>
>> @@ -482,8 +482,10 @@ struct sctp_chunk *sctp_process_strreset_inreq(
>> }
>>
>> chunk = sctp_make_strreset_req(asoc, nums, str_p, 1, 0);
>> - if (!chunk)
>> + if (IS_ERR(chunk)) {
>> + chunk = NULL;
>> goto out;
>> + }
>>
>> if (nums)
>> for (i = 0; i < nums; i++)
>> --
>> 2.1.0
>>
>>
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