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

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>
This commit is contained in:
Tomas Bortoli 2018-07-23 20:42:53 +02:00 committed by Dominique Martinet
parent 430ac66eb4
commit 9f476d7c54
1 changed files with 5 additions and 5 deletions
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10
net/9p/trans_fd.c
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@ -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
@ -375,8 +374,9 @@ 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;