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Commit 4cd19526 authored by Tomas Bortoli's avatar Tomas Bortoli Committed by Greg Kroah-Hartman
Browse files

net/9p/trans_fd.c: fix race by holding the lock 

[ Upstream commit 9f476d7c540cb57556d3cc7e78704e6cd5100f5f ]

It may be possible to run p9_fd_cancel() with a deleted req->req_list
and incur in a double del. To fix hold the client->lock while changing
the status, so the other threads will be synchronized.

Link: http://lkml.kernel.org/r/20180723184253.6682-1-tomasbortoli@gmail.com


Signed-off-by: default avatarTomas Bortoli <tomasbortoli@gmail.com>
Reported-by: default avatar <syzbot+735d926e9d1317c3310c@syzkaller.appspotmail.com>
To: Eric Van Hensbergen <ericvh@gmail.com>
To: Ron Minnich <rminnich@sandia.gov>
To: Latchesar Ionkov <lucho@ionkov.net>
Cc: Yiwen Jiang <jiangyiwen@huwei.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: default avatarDominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5859129c

net/9p/trans_fd.c

+5 −5
Original line number Diff line number Diff line
@@ -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 int
@@ -385,8 +384,9 @@ 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);

		/* update req->status while holding client->lock  */

		p9_client_cb(m->client, m->req, status);

		spin_unlock(&m->client->lock);

		m->rc.sdata = NULL;

		m->rc.offset = 0;

		m->rc.capacity = 0;