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

BugLink: https://bugs.launchpad.net/bugs/1835972
[ 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: Tomas Bortoli <tomasbortoli@gmail.com>
Reported-by: 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: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index ef63ff6c2cee4d6b8cffbabed24ccbd8f69d49fe..774ff67f4dec3a90e7dd3d4f67e163f902375a03 100644 (file)
--- 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 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;