On 2018/7/23 20:19, Tomas Bortoli wrote: > 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 <tomasbort...@gmail.com> > Reported-by: syzbot+735d926e9d1317c33...@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);
If you want to expand the ranges of client->lock, the cancel_list will not be necessary, you can optimize this code. In addition, we delete some person because too many recipients are limited. Thanks, Yiwen. > } > > 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: >