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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+4c9934f20522c0efd657@syzkaller.appspotmail.com,
        Xin Long <lucien.xin@gmail.com>,
        Neil Horman <nhorman@tuxdriver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.20 17/52] sctp: remove sched init from sctp_stream_init
Date:   Mon, 18 Mar 2019 10:25:04 +0100
Message-Id: <20190318083845.494264659@linuxfoundation.org>
In-Reply-To: <20190318083843.398913295@linuxfoundation.org>
References: <20190318083843.398913295@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 2e990dfd13974d9eae493006f42ffb48707970ef ]

syzbot reported a NULL-ptr deref caused by that sched->init() in
sctp_stream_init() set stream->rr_next = NULL.

  kasan: GPF could be caused by NULL-ptr deref or user memory access
  RIP: 0010:sctp_sched_rr_dequeue+0xd3/0x170 net/sctp/stream_sched_rr.c:141
  Call Trace:
    sctp_outq_dequeue_data net/sctp/outqueue.c:90 [inline]
    sctp_outq_flush_data net/sctp/outqueue.c:1079 [inline]
    sctp_outq_flush+0xba2/0x2790 net/sctp/outqueue.c:1205

All sched info is saved in sout->ext now, in sctp_stream_init()
sctp_stream_alloc_out() will not change it, there's no need to
call sched->init() again, since sctp_outq_init() has already
done it.

Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Reported-by: syzbot+4c9934f20522c0efd657@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sctp/stream.c |    2 --
 1 file changed, 2 deletions(-)

--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -230,8 +230,6 @@ int sctp_stream_init(struct sctp_stream
 	for (i = 0; i < stream->outcnt; i++)
 		SCTP_SO(stream, i)->state = SCTP_STREAM_OPEN;
 
-	sched->init(stream);
-
 in:
 	sctp_stream_interleave_init(stream);
 	if (!incnt)