From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomas Bortoli Subject: [PATCH] net/p9/trans_fd.c: fix double list_del() Date: Mon, 23 Jul 2018 14:19:02 +0200 Message-ID: <20180723121902.20201-1-tomasbortoli@gmail.com> Cc: asmadeus@codewreck.org, jiangyiwen@huawei.com, davem@davemloft.net, v9fs-developer@lists.sourceforge.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller@googlegroups.com, Tomas Bortoli To: ericvh@gmail.com, rminnich@sandia.gov, lucho@ionkov.net Return-path: Received: from mail-lj1-f194.google.com ([209.85.208.194]:42351 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387910AbeGWNUY (ORCPT ); Mon, 23 Jul 2018 09:20:24 -0400 Sender: netdev-owner@vger.kernel.org List-ID: A double list_del(&req->req_list) is possible in p9_fd_cancel() as shown by Syzbot. To prevent it we have to ensure that we have the client->lock when deleting the list. Furthermore, we have to update the status of the request before releasing the lock, to prevent the race. Signed-off-by: Tomas Bortoli Reported-by: syzbot+735d926e9d1317c3310c@syzkaller.appspotmail.com --- net/9p/trans_fd.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index a64b01c56e30..370c6c69a05c 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -199,15 +199,14 @@ static void p9_mux_poll_stop(struct p9_conn *m) static void p9_conn_cancel(struct p9_conn *m, int err) { struct p9_req_t *req, *rtmp; - unsigned long flags; LIST_HEAD(cancel_list); p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err); - spin_lock_irqsave(&m->client->lock, flags); + spin_lock(&m->client->lock); if (m->err) { - spin_unlock_irqrestore(&m->client->lock, flags); + spin_unlock(&m->client->lock); return; } @@ -219,7 +218,6 @@ static void p9_conn_cancel(struct p9_conn *m, int err) list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) { list_move(&req->req_list, &cancel_list); } - spin_unlock_irqrestore(&m->client->lock, flags); list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) { p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req); @@ -228,6 +226,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err) req->t_err = err; p9_client_cb(m->client, req, REQ_STATUS_ERROR); } + spin_unlock(&m->client->lock); } static __poll_t @@ -370,12 +369,12 @@ static void p9_read_work(struct work_struct *work) if (m->req->status != REQ_STATUS_ERROR) status = REQ_STATUS_RCVD; list_del(&m->req->req_list); - spin_unlock(&m->client->lock); p9_client_cb(m->client, m->req, status); m->rc.sdata = NULL; m->rc.offset = 0; m->rc.capacity = 0; m->req = NULL; + spin_unlock(&m->client->lock); } end_clear: -- 2.11.0